Car Corner: Base Engine Testing

hi welcome to car corner my name is Richard Saxton I'm the coordinator of the automotive programs here at the Community College of Philadelphia in today's episode Dan Reid is going to get your engines revving with his discussion on base engine testing if you have any questions about the automotive programs here at the college please check this out at the website okay now it's time to get your car in gear hi I'm Dan Reed with Community College of Philadelphia welcome to car corner today we're going to be talking about what happens on the inside of an internal combustion engine more specifically what happens when parts fail and really why the mechanical parts inside an engine break and what happens when they do break and it's interesting to note that all of the layers of the electronics that modern cars come with today at their core they still share the same exact basic parts that the original internal combustion engines did from the very first automobiles and gas engines ever produced the fact is is that those core parts still don't actually have any electronics attached to them we can actually use the world of physics at our disposal to measure to determine whether or not those components are functioning properly so first let's talk briefly about some of the basic components that are inside a four cycle internal combustion engine what we have here on the bench is this is what's known as a cylinder head now a cylinder head is a large metallic component that sits on top of the engine block assembly inside the engine block assembly we have things you may have heard of before pistons and a crankshaft and a oil pump and things like that cars still have them and they've always had them the cylinder head itself contains components like camshafts and valves those are other components you may have heard of as well so this type of camshaft is what's known as an overhead camshaft cylinder head what it is is its first of all it's made out of aluminum they used to be made out of cast iron today since probably the mid-1970s manufacturers started making them out of aluminum because it was lighter weight and anything that saves weight helps save fuel which makes cars faster and more fuel efficient so our cylinder head itself is made out of aluminum which is a relatively soft a weak metal when compared to things like cast iron but it works great and it's where it's located it doesn't get too hot and it's cooled pretty well these components here across the top these are what's known as valve springs now valve springs are attached to valves and I got a couple valves here the valves themselves can come in different sizes depending on the size of the engine and if it's a different type of internal combustion engine like say a locomotive a diesel locomotive or a tugboat or something like that the components just get larger as those engines physically get larger if we have something small like a lawnmower perhaps the components just get smaller so they're pretty scalable for a lot of different cars and valves generally work pretty pretty quietly they don't really do much of anything in terms of the way of having explosive forces occurring inside of them but what they do is they allow an opening closing of the cylinder head to allow fresh air in and exhaust gases out and one of the things that can happen with valves is that the valves themselves can actually Bend and if you've ever heard somebody say all of the cylinder head has a bent valve that's what a bent valve looks like the valve is supposed to slide up and down and it's a housing called a valve guide and if the valve gets bent it can't slide anymore and likewise if it's sliding up and down like this it's not closing properly against its ceilings surface inside the head if we look at the underside of a cylinder head we can see the undersides of these valves in cars typically are going to have at least two valves sometimes more per cylinder and on this engine we have intake and exhaust valves and the way this engine is laid out these guys are actually the I believe these are the intake valves and these are the exhaust valves the shape on the underside of the cylinder head is is dictated by the engineering requirements of the car what type of car it's supposed to be the fuel economy it gets that type of thing hot rodders like to modify this area of the cylinder head so when they talk about doing cylinder head work this might be one of the areas by changing the shape of this we can change how the combustion process happens when it happens in that type of thing so these valves open and close and this valve right here is in is in a open state the valve itself is off the seat and with the cylinder head on the engine block deck with the valve open what that's going to allow is that's going to allow air in or out of the combustion chamber this round area right here is where my Pistons would be sitting so the Pistons are going to come right up against the underside of the cylinder head and then they're going to allow air in and out through these valves so a couple things worth mentioning about the cylinder head and the valves while we're here you can see this residue on the cylinder head and what this is is this is residue left over from a component which separates the cylinder head and the block assembly called a head gasket a head gasket has a really really difficult job because not only is it is it making sure that the cylinder head seals against the engine block but you can see also that there's these holes and ports all around here and what we have is sometimes we'll have oil or will have coolant passing in and out of those ports as we lubricate components or cool components so a head gasket is is a is an important part it's really a sealing surface but it also helps separate and make sure that we don't mix and combine coolant oil oil being oil and coolant being mostly water oil and water don't mix and we certainly don't want that mixing inside our engine when you have a cylinder head gasket fail you have to remove the cylinder head generally we have to clean the cylinder head and inspect it and that can be that can be a pretty big job removing a cylinder head from a car's time-consuming and it's too long can be a long and expensive process so we try not to have too many cylinder head failures with our with in terms of head gaskets all right so the the other component I'm going to swing this around here going to point this around the front is we have this cog on the end of the cylinder head this is attached to the camshaft in the engine and normally we'd have a rubber toothed belt that would attach this cog on the camshaft down to another cog on the crankshaft of the engine so as the crankshaft turns it's going to actually be connected to the COG of the camshaft and that in turn is going to help us open our closure valve so before I get too deep into the rest of the engine functions I want to go over exactly how an internal engine works so let me grab a couple components here and we'll sort of set this up here on the bench and first we're going to have our piston and the piston is going to be in the lower half of the engine in the block and then we're going to have two valves I'm going to have an intake and an exhaust valve and what I'm going to do with these is I'm going to talk about how the engine functions so what we're going to do is sort of have a little diorama here set up air and fuel are going to have to come into the engine now the piston is going to be able to travel up and down in its cylinder and these valves are going to be able to open and close and then we're going to have a spark plug there in between the two and the first cycle out of a four cycle engine which is another term you may have heard of before there's four cycles to actually get the piston to do any work so the first cycle is known as intake and what we do on the intake so I as we open our intake valve and the piston is at what's known as top dead center it's the highest the piston goes inside the block and the piston starts to get drawn downward by a crankshaft the crankshaft works just like the cranks on a bicycle if you could imagine your feet literally being the Pistons as you're turning that crank you're turning that center bar and that's actually going to ultimately be attached to the transmission and drive the wheels of the vehicle so our piston goes down and as our piston goes down it creates a negative air space vacuum and with the intake valve open what we're doing is we're going to take in a nice gulp of air and fuel and we're going to have another component which is going to be on the back side of the intake valve and that is our fuel injector so the fuel injector is going to spray some gasoline when that valve is open and it's going to get sucked into the chamber the combustion chamber of the engine at that point once we have the piston all the way at bottom dead center this section is now filled with a volatile air & fuel mixture but it's not quite ready for primetime yet we really have to compress that air fuel mixture to really extract that energy from it so as the piston starts to travel back up what we do is we close off our intake valve and I'm going to take the fuel injector away because we don't use that anymore at this point and the piston is going to travel up as the piston travels up the next cycle is what's known as compression and that's when we compress our air fuel ratio now I've squeezed this air fuel mixture and when I squeeze it it gets very hot and it's very volatile and when people talk about compression ratios and engine and engines literally the amount that we compress the piston as it comes up as we compress that air fuel mixture with our piston that volume of compression is our air as our compression ratio once we get this as high as it's going to go we're going to light off our spark plug and at that moment right then we start to create a flame front from our spark plug that's going to travel down up against the crown of our piston the piston at this point is now in powerstroke we have a controlled burn that's going to actually force the piston back down and that is the only point of which out of the four cycles we do any work that power stroke is what actually produces the energy to force the piston back down once we have the piston all the way again at bottom dead center the piston has to travel back up and the reason why is because we actually have a bunch of exhaust gas now in the cylinder we have to evacuate that gas so the last stroke or cycle that we have is what's known as the exhaust stroke the piston now is at bottom dead center and what I have is I have a cylinder full of exhaust gas what I'm going to do is I'm going to open the exhaust valve and I'm going to push the piston up as the piston travels up it's going to push out those collected exhaust gases out through the exhaust port of the cylinder head which goes into the exhaust manifold and then down to the catalytic converter and the muffler and out the tailpipe once the piston has reached top dead center I'm going to close that exhaust valve and I'm going to start to open my intake valve and at that point the piston is going to start to travel back down as does I'm going to bring my fuel injector back in it's going to spray some fuel in piston is going to travel back down to bottom dead center again and this entire cycle repeats so the cycles our intake compression power exhaust intake compression power exhaust each cylinder of the engine goes through those four cycles of operation as the engines running the other thing that I can show you is that I have an engine right here on a stand and let me bring that over so I can kind of demonstrate some of these components while they're all in motion and how their time together so what I have here is this is a modern dual overhead cam v6 Toyota engine block and it's an all aluminum engine so the block the lower half here is aluminum the Pistons are steel and then we have two cylinder head banks right here and what we have is instead of a belt this vehicle design uses a chain it uses a large bicycle chain like link chain together to make sure that the crankshaft down here is timed with the camshafts and while the engines turning you can see how this would all move in sequence and one of the things that technicians like my students who took this engine apart and then expertly put it back together did is you have to be very very careful when we're working with timing chain assemblies or timing belt assemblies to make sure that we get these components all lined up right you just can't put the chain back on like a bicycle and everything will be okay the fact is is if the piston is at the wrong section of the stroke while a valve opens at the wrong point the engine literally won't run even though you may have put it back together correctly so timing chain assemblies and timing belt assemblies or something that you know if you don't know what you're doing you should not mess with inside the engine and you may notice these these links these colored links here on on the chain that is designed for the technician when they go to line this up there's literally marks that they're going to have to line up on the camshafts and the crankshaft to line up with those chains so they know exactly where everything goes when they go to put it back together so again this is the operation and you can see that as I turn the crank the chain is pushing my camshafts around and they're turning and what I'm going to do now is rotate the engine sideways so you can see the camshafts pushing down on the valves which is going to open and close the valves and then what I have is I have a special camera that can show us what's happening inside the engine as I turn it and we can take a look at it in real time and see what's happening so let me turn this and put this guy right here so on the cylinder head this this cylinder Bank right here this is the exhaust camshaft and so exhaust gases would come out here this is the intake camshaft and what we have is we have a set of lobes these pointy parts right here on the camshaft are what's known as camshaft lobes they're going to swing around and push down on top of the valves and actually open the valve so when you see these lobes up in this direction it means those valves are actually closed when the lobe comes around it actually pushes down on the valve and forces the valve open which is going to at that point allow an air fuel mixture to come in so let's take a look at that as that rotates around see how that all works now well this is happening inside the engine it's happening literally so fast that you would just see it as a blur the other thing is is we have a cover on here called the cam cover used to call it a valve cover and there'd be a rubber gasket in between here and there'd be I'll slinging around on the inside of this and that's part of the lubrication system but let me get my borescope and show you exactly the operation of these valves opening and closing we can see we'll be able to see the piston go up and down inside a cylinder so what I want to do is I have a tool called a video borescope and the video borescope is a camera on the end of a wand and what I'm able to do is I'm going to show you what happens to the piston on the inside of the combustion chamber while the engine is running so I'm going to drop this in and I'm putting this in through the spark plug port and when we come down through the inside here what we're looking at that silver disc is the head of the head of the piston and when I crank the engine over we're going to see that start to come up and when it reaches its highest point that's what's known as top dead center as the piston starts to drop away inside the combustion chamber we can really start to see the entire piston we can kind of look we can see a little bit of the cylinder walls inside there and some of the other parts of the in the where the combustion process takes place so this tool is really useful because it allows a technician to basically look inside an engine without having to actually take anything apart and if you had an engine where maybe either was a possible issue you know this would just basically help a technician find what the problem just verify what the problem could be not necessarily use this to fix anything but just help verify the diagnosis the other thing we can do here is I can pull this out and we can look at the inside of the intake valve and it was I crank this open as this camshaft comes around on the top here should be able to see those valves open on the inside just right there so by looking at you know say the intake valve or an exhaust valve or the head of the piston with a borescope you know again it just gives the technician a good idea of what's going on inside the engine and allows me to do an inspection without having to really disassemble the entire engine so that's that's pretty useful so now that we have a good idea of what the main components are inside our engine let's take a look at some of the tools that we're going to use to actually diagnose an engine performance concern in other words what's going to happen when we go through and try to figure out what's wrong with one of these components so now that we have a good idea of what some of the components are inside the engine and how they go together let's take a look at some of the basic tools that a technician is going to use to determine the overall engine health or what the problem might be now again these tools go back to the first internal combustion engines and literally if I took these tools and I went a time machine back to 1920 I could use all of these tools on a car from 1920 and I would get pretty much the same results that I get from a car from today in terms of what I would expect and how the car would function so you'll note there's no scan tools here there's nothing really fancy high-end expensive tools for me to plug into a diagnostic port or anything like that when you have an engine that runs poorly you really have to start with the basics and that's what these tools help give me a framework a baseline kind of the overall engine health inside the car so the first test that we have the first tester that I have here is is what's known as an engine compression tester and what this is is this is a pressure gauge and we screw this into the spark plug port of an engine and then we crank the engine over and we use the electric starter motor and based on the amount of pressure that we develop in the cylinders it's going to tell us a couple things it's going to tell us is you know is the intake valve opening on the intake stroke to let air in is the engine able to compress an air fuel mixture and if so what is the pressure of that air that we're going to be able to compress our air fuel mixture to when we actually look at it on the gauge so the compression gauge is going to be able to tell me exactly how much pressure we can develop in the cylinder specifically how much compression can we make on the compression stroke if I can make you know something over maybe a hundred psi and that's what the manufacturer calls for that's a that's a good number that's going to tell me that the internal operation of that cylinder is functional the intake valve and the exhaust valve are opening and closing they're sealing properly and then the Pistons and cylinder walls are all in good shape as well so that's really going to be a useful test the other gauge that I have which is really kind of an old-school tool is what's known as a vacuum gauge and a vacuum gauge hooks up to a line behind the throttle plate on the intake manifold and what it allows me to do is measure the relative vacuum or suction that the engine is developing now if you remember back to the four cycles of engine operation the intake stroke that piston is coming down is creating a negative air space and we're going to draw in an air fuel mixture I'm able to measure that suction of that piston with a vacuum gauge and generally speaking a good healthy engine while its operating should be somewhere between maybe 17 to 22 inches of mercury on my gauge and the needle should be steady it shouldn't it shouldn't bounce it shouldn't waver around as the cars running if I open and close the throttle while the engines running I'm going to get movement on my vacuum gauge and that's fine but again I'm kind of looking for a nice steady non vibrating needle reading here with my vacuum gauge somewhere between 17 and 22 if I have that chances are the overall engine health is really good in fact if I go to actually buy a used vehicle a lot of times I'll hook up a vacuum gauge just to kind of give myself peace of mind that I know that the internals of the engine are good if I there's a problem with an intake valve or an exhaust valve or a piston that needle is going to fluctuate as that cylinder has that fault and you're going to see it on the gauge so it doesn't really tell me exactly what's wrong with the inside of the engine or which cylinder is at fault but it is going to tell me exactly that the engine has an internal engine problem and I have to do further diagnosis the last gauge that we have is what's known as a cylinder leakage tester now this is a diagnostic tool that you have to have a compressed air source for and I'll demo this later on the engine but what we do is we hook up a compressed air outlet here from our air compressor on the shop there's a regulator attached and what we do with this end is we actually blow compressed air into the cylinder and what this gauge over here with the red the yellow and the green indicates is this is the amount of air that's leaking out of the cylinder versus the amount of air I'm pumping into the cylinder so if the cylinder isn't sealing somewhere I'm going to be able to get a relative reading of exactly how much of this is actually how much air is leaking out and obviously I want it to be somewhere in the green area to tell me that the engine that that specific cylinder doesn't have a fault so there's two other pieces as well and these are just going to help me with something known as misfire diagnosis now this this piece right here this is a spark tester and what this does is this looks a lot like a spark plug and what I do with a spark tester is I disconnect the spark plug boot from the engine I connect it to this end of the tester and I ground the this end of the tester somewhere on the engine block and when I crank the engine what I'm going to see is I'm going to see a nice I should see a nice bright blue purple spark here on my spark tester if I see that that means that the ignition system is probably functioning and that it's going to be the reason that the engine is you know the ignition system is functioning okay so it's not the reason why the engines running poorly however I could still have a problem with a spark plug but since we're going to take them out anyway when we do a compression test well we'll see what we got there the last piece I have and probably the more modern piece of test equipment which I might have is what's known as a noid light or an injector light what these testers do is they are basically 12-volt lights they're very small and we can plug these into the fuel injector harness of our car when we run the car the fuel injector is going to open and close and Alette fuel into the cylinder as the intake valve opens that fuel injector works on an electrical signal so if I remove the injector and I replace it with a light bulb the light bulb should blink as that injector opens and closes so what these allowed me to do is these little metal prongs here allow me to plug into the injector harness and then actually go through and see if the injector is getting power and if I get a blinking light here while the car is running at that injector it means that that injector is the wiring and the computer and everything back back from there is good and there could be a fall possibly with a width injector but chances are that's not the problem so all right let's take these let's move these tools out of the way and I just want to briefly switch back here for a second and I just want to talk about Pistons and going back to the piston in terms of damaged pistons have rings the Rings are what's going to seal inside our cylinders and these rings generally when the when it's in the engine these ring these gaps are going to close up very tight these top two rings what they do is they seal the combustion chamber this last ring this what's known as a three piece oil control ring is what helps control oil from getting into the combustion chamber we do lubricate the cylinder walls a little bit and this special ring acts like a squeegee so the ring is really used to squeegee the oil back down into the crankcase it's not used for combustion gases remember the head of the piston of the crown of the piston is what we saw on the inside of that other engine and this is where you know I have a lot a lot of heat damage and things like that this is really the part that really gets punched in the face while the engine is running along those lines if we have a defect with our engine you can see the difference these are not from the same engine but you can see that piston damage can definitely occur inside an engine this engine had some mechanical damage and we can see that the area where the Rings sit the ring is actually broken it's cracked and then we have all the scoring on the skirt of the piston this engine obviously was was done it was there was no saving at at this point you can't fix this with any type of special additive to the oil or anything like that this has to come out at that point and be replaced and what we ended up doing was just actually replacing the entire engine because every cylinder and this engine looked as bad but that happened in part because of a some serious neglect on the owners part basically they ran the wrong fuel in it and it was also had the wrong whale in it and consequently it didn't last too long after they did that so now that we're done taking a look at our pistons let's take a look at the car behind me which has a genuine engine performance problem so what we have here is we have our Honda Accord and it has possibly an internal engine problem it has it has a misfire which is a way of saying out of the four cylinders one of them doesn't seem to be contributing any power now what we're going to do is we're going to run through a couple basic tests and this car will start and run but it but it runs badly it runs poorly it misses it has a lack of power and you can you can act we hear that the car doesn't sound right while it cranks and consequently if it doesn't sound right when it cranks there's a good chance that there's internal something going on internally with this engine doesn't have to be catastrophic but it's probably not going to be an easier cheap repair but we can narrow down our Diagnostics using some of the tools that we've talked about from before so let's get on with it what I'm going to do is I'm going to I'm going to turn turn around I'm going to turn the ignition on and then what I have is I have a remote starter switch here and what that's going to allow me to do is start the vehicle from outside the car and this is necessary when you're doing a compression test or something like that because I have to be able to look at the gauges while the car is running and I want to be able to start the car from underneath the hood so that's why I have this gauge just remember if you do use a remote starter switch make sure the car is not in gear if the car starts and runs while it's in gear the car will literally just drive and run you over so please be very very careful while you're using a remote starter switch okay and start the car up yeah doesn't run great that that stutter we shut that off that stutter is a classic sound of an engine misfire what that means is that one of these cylinders is literally just not doing its job the reason why the engine was kind of jumping around so much is because out of those four cylinders they're all balanced against each other and they're balanced literally against the amount of energy that they'll produce if one cylinder is not producing enough energy it throws the engine out of balance and we get that shaking roughness which US technicians refer to as misfire so the question is is what cylinder is is misfiring and what we're able to do is we're going to do a quick test here where I'm going to unplug a fuel injector while the engines running and what that's going to do is that's going to determine if the engine runs any any better or worse and if the engine does not seem to change while I had that injector unplug there's a good chance that that's the cylinder that I can focus my diagnosis on that test is referred to as a power balance test some newer cars have the ability to do a power balance test through the computer the technician can literally command the computer do one this vehicle doesn't have that ability so we have to do on the old-fashioned way so we'll just give it a shot the other thing I'm going to do is we're going to hook up my vacuum gauge here and I'm going to be able to take a look at my engine vacuum and try to figure out exactly if I have an internal engine problem if I do we'll just have to dig a little deeper so let me unplug this line here and hook up my vacuum gauge right here position this guy all right you know turn the ignition back on I'll give this another try well remember I talked about the needle dancing around if there's a problem yet this car definitely has something internal going on so let me shut it off all right you saw how much that needle was jumping around while the car was trying to idle and again that is a classic sign of an internal engine problem so what I'm going to do is the engine actually doesn't really run well enough for me to try to figure out exactly which cylinder is a fault so what I'm going to do is I'm just going to start with a compression test I have a good clue that that's what the problem is because because of the needle movement on my vacuum gauge so to start a compression test what I'm going to do is I'm going to pull out the spark plug boots and if I had to these ones are basically installed by length so I don't really have to label them but if I had something like a v8 or v6 I'd be very careful to make sure that it labeled these so they went back in the correct cylinders I wouldn't want to mix that up so let's get started on that the next thing I'm going to do is I'm going to pull the spark plugs out and when I do this I'm going to use a ratchet and a socket with an extension and a special socket called a spark plug socket now the spark plug socket has a rubber grip on the inside of it and what it's going to allow me to do is make sure I can pick up that spark plug when it falls out so it doesn't fall down inside the tunnel that it's in if I don't have a special spark plug socket it's probably okay to still use another socket but these are pretty inexpensive and they do a great job it can be a little difficult when you go to reinstall the spark plugs when we're all done here to make sure that everything is lined up sometimes you can use a magnet or a piece of vacuum hose to pull them out put them back in but we have the right tool so we'll use that you as I do this if this area the engine was really really dirty or anything I'd actually want to blow this out maybe with some compressed air to make sure I didn't have any debris fall inside of the engine I don't want to make things any worse than they already are the other thing is is as I pull the plugs out I'm going to be getting some clues the fact that this plug is sort of dark darkish color almost like a like a charcoal color gives me the indication that this engine has not been run long enough to have the plug breach it's self-cleaning temperature if this gets really bad it's referred to as carbon fouling and the plugs when they come out should be kind of like a wait ish like almost like a biscuity color like a color of a like a sandwich biscuit or something like that the other thing I want to do is I want to make sure that it keeps these in order because I can gather clues by that on terms of my diagnosis so this is number one there right there go into number two yeah take a look at this here's plug it looks nothing like the plug I just pulled out and it smells like gasoline what I got is I definitely have some some difference in color now this tells me that if it smells like gasoline I could have a stuck open injector or I could have combustion not occurring in that cylinder because maybe there's internal engine damage which takes me back to the fluctuating vacuum gauge so we'll keep this guy's cylinder number two and we'll move on take a look at the other plugs in Tripoli there's plug number three and that looks a lot like the first plug we've pulled out and then this is plug number four and that plug also looks pretty pretty much like one and three so this cylinder right here too is definitely my suspect cylinder now the next step I'm going to do is I'm going to do a compression test and the basic rules of a compression test are is first of all I don't want the ignition on I actually have to disable the the ignition coil if I'm going to use the ignition key and I'm going to unplug my fuel injectors back here to make sure I don't have any fuel spray into the engine while I'm cranking it now I don't have to really worry about that because I'm going to be using this remote starter switch which I have hooked up but if I were to use the ignition key I'd also definitely want to make sure I disabled my ignition system if not I'd get shocked and that won't feel good and more importantly aside for me getting hurt I also run the risk of burning out the computer on the car because running the ignition system open can cause a surge of electricity to go back and actually fry the computer so to make sure that doesn't happen plug this line back in alright the next thing I have to do is I have to make sure that I get a screw driver and I block the throttle plate open I want to make sure that I hold that throttle plate open while I crank the engine and I'm also going to go get a booster pack for my battery I have to make sure that the engine cranks at the same speed for each cylinder so I get a consistent reading so let me get those tools and I'll be right back so I'm going to take a screwdriver and I'm going to block my throttle plate open and that's important to do because I want to make sure that I hold the throttle plate wide open so that way as I crank the engine I get a good gulp of air into the cylinders it's an important step you shouldn't forget it if you are doing a compression test the other thing I have is I have a booster pack right here and what I'm going to do with this is hook it up to the car battery that way I have a good power source to keep the starter spinning at a constant speed while I do my compression test there we go all right so now that I've got my engine all set up what I'm going to do is I'm going to take my compression gauge and I'm going to thread it into the first spark plug hole so a couple important things to keep track of when you do a compression test normally I'd write down all the numbers now on a four cylinder it's not too hard to remember all the numbers that you get but when you do something like a v8 or v6 or a v12 or v10 it's good idea have a notepad handy so you can keep track of the numbers that you get when you run this test the other thing is is the test is an interpretation manufacturer of this car says that minimum compression spec is a hundred and twenty psi so that's a minimum number I'm looking for each cylinder but really when we do a compression test what we're looking for our values within ten percent of each other so when you do a compression test you actually have to do it on all the cylinders at the same time you have to take all the spark plugs out because cylinders actually can leak into one another through that head gasket so let's see what we get when we go through here and do this when we run our compression test I'm going to double check first and make sure my ignition key is added the ignition and it is out of the ignition and I'm ready to run my test now my gauge hooks up with a collar to the port where I plug it in there's no tool I just use the torque of my hand to actually tighten this down and there's a thumb release a pressure release on the side of the gauge I have to make sure I don't have my thumb on that as I crank the engine over so I'm going to crank my engine over I look at my gauge and see what I get I'm going to crank it four times you'll hear the engine turn over one two three four and that final gauge reading is what I'm going to get out of the cylinder so you like that jump yeah I forget about how loud that can be you try that again so let me take a look at my gauge and let's see what we get and when we got there I got about looks like almost 200 psi now that's pretty good the manufacturer says the minimum minimum was 120 to 200 is is great if I have really high compression on all my cylinders what that can indicate is that I have carbon buildup inside the engine generally carbon buildup is going to lead to a possibility of the engine actually running too hot or overheating possibly failing an emissions test it's not really going to affect necessarily how the engine starts and runs but it's something to watch out for and it's interesting to see how high it is on this engine this is one of our school cars and it doesn't really don't drive our cars here at the school we run them in class but we don't take them out on the highway and blow them out like you would with your personal car so I'm not surprised that there's some carbon buildup in here but let me release this and we'll go on to cylinder number two and here we go with cylinder number two that doesn't sound too good does it and you can you can hear that the engine doesn't sound like it's doing anything with cylinder number two in fact it's just freewheeling and I have absolutely no compression on my gauge that's a problem that means that cylinder number two has no compression cylinder number two is that on the compression stroke nothing is happening so that means that the air is either not getting into the cylinder or the air that we're getting into the cylinder isn't able to be contained in the cylinder and we're losing some of that air one of the tricks that we can do at this point is we can actually take a little bit of oil and pour it into the cylinder and then rerun the test the idea is that while the oil sits on the head of the piston which is basically the floor of my combustion chamber if those rings are bad the oil is going to help seal those rings a little bit and I should get the gauge to go up if I don't get the gauge to go up that means that is the intake valve or the exhaust valve or possibly the head gasket is at fault where I have a major major failure on the cylinder with the Rings or the head of the piston so let me get some well and we'll take a look at that so this is my oil squirter when I squeeze the trigger puts out about one tablespoon of oil it's important at this point to realize that you don't want to basically you don't want to flood the cylinder with oil I just want to put a couple squirts in there wait a second and then rerun the test so give this a shot there's one and there's two wait a second and right now the oil is running down the inside of the cylinder hopefully it's sealing things up if not we're going to see what we get that oil made absolutely no difference whatsoever so that means that the problem in cylinder number two is either the intake valve the exhaust valve or there's a catastrophic failure in that cylinder so at this point we're just going to move on and we'll check cylinders three and four just to make sure that there's no issues with them there's a possibility if it was the head gasket that had failed that cylinder 3 and cylinder 2 could actually be leaking compression into each other so I want to make sure that I check cylinder 3 before I go on with the rest of my diagnosis yeah and cylinder 3 got to 210 psi definitely within 10 percent of cylinder number 1 which was 200 psi so will vent that and because it just takes a second we'll do cylinder number 4 and that way we'll have a good baseline across the board yep 2:10 again so cylinders 1 3 & 4 have excellent compression cylinder 2 has no compression so at this point the news isn't good we know that there is definitely a problem with the internals of this engine and specifically it's either with the most likely with the valves on cylinder number 2 but I can still do a little more diagnosis if I were going to tell a customer exactly what the problem was at this point they're looking at an expensive repair bill so I want to give them the most accurate diagnosis I can so the other tool that I'm going to use now is now that we know that cylinder number 2 as a problem is we're going to use our cylinder leakage tester and I'm going to hook up a compressed air line to this what I have to do first though is there's a another gauge that I put in here what I have to do is I have to bring that cylinder number 2 to top dead center and I have to make sure that both my intake and exhaust valves are closed so what I have is I have another piece that looks just like it's part of the compression tester I'm going to screw this in but it has a whistle attached to it and when we hear the whistle what I'm going to do is I'm going to stop turning the engine now my whistle is this little guy right here and what I'm going to do is I'm going to take a breaker bar and I'm going to go down onto the crank shaft of the engine and I'm going to manually rotate the engine and when I hear the whistle start to whistle I'm going to stop rotating the engine now the whistle want to hear it means that both my intake and exhaust valves are closed and they should be sealed and also the piston is on its upward stroke so let me get that done okay so I got my whistle and I'm going to hook up my compression gauge on cylinder leak down tester get this set up and I'm going to blow air into the cylinder so what I have now is I have some compressed air I'm going to force into the cylinder now as I do this I'm going to listen specifically for a couple things if I hear air hissing out of the tailpipe of the car it means an exhaust valve is stuck open if I hear air hissing out of the throttle body it means that the intake valve is stuck open and I'm going to do two things I'm going to take off the oil cap if I hear air hissing out of here it means my rings are damaged and I'm going to take off the radiator cap and if I see bubbles out of my coolant it means my head gasket has failed so let's hook it up and see where we have our leakage and how much leakage we have and right here while this is running you can see the gauge immediately went to almost the red zone of my tester which means I have pretty much high leakage I have a high cylinder leakage now I don't feel any air coming out of my oil fill cap I can put my hand over it I don't really hear any change there so I know that the Rings are okay and I can see over here in the in the radiator I don't have any bubbles I don't hear any bubbles coming out of my coolant so that means it's either out of the the intake manifold tip little screwdriver out I don't really hear any air changing there so what that probably means is that my air is escaping out of my tailpipe at this point and that would lead me to a problem with one of the exhaust valves and cylinder number two I could go back and I could listen to that and I'd probably hear or feel a little bit of air the air that I'm pumping into this is basically leaking in through this hose going into the cylinder and it's forced out through the exhaust manifold as the as the system's pressurized so what I'm going to do now is I'm going to go back and I'm going to use that borescope and we're going to look inside the cylinder and see what we find in terms of a of a possible fault now generally when a shop does this if it's a four-cylinder engine you can see that it doesn't take a real long time to do this test most shops will charge you in an hour which is a very fair labor rate for base engine Diagnostics like this the more cylinders the engine has or the more difficult the cylinders are to get to the longer that test can take so if you had something like a v8 or v6 where maybe four of the plugs are very hard to get to in the back of the engine this test could actually take possibly two hours to do so let me get the borescope and we'll take a look inside the cylinder and see what we find so what I have on the borescope is I have an angle adapter and what this is going to do is it's going to allow me to look at the sides of the cylinder walls it should also allow me to see the intake valves in the exhaust valves and see if we have any damage or of anything stuck open so let's take a look going to cord and going down through the inside here and making my way down inside the cylinder clean this guy off so there's the threads on the spark plug one right down there that's the threads on the spark plug so now we're inside the combustion chamber and can I see anything inside here this guy around pull this angle adapter off and it's hard to see what I'm looking at right there isn't looking at the head of the piston and I can see all that oil that I put in there when I did that that wet part of the compression test didn't change much so that actually looks okay I don't really see any damage here on the the sides of the cylinder walls they look okay I don't see any scoring or damage and pull this out and put our angle adapter back on and see if we can see anything and to get a look turn this around and right there that line that line right there that is the lip of my exhaust valve hung open and that shouldn't be hung open that guy should be closed it should be sealed up at this point so that tells me that one of the two exhaust valves on cylinder number two are stuck open just like our tests showed us so this engine is unfortunately going to probably have to have the cylinder head examined and come off and at that point we'll be able to to come up with a full workup of exactly what it needs but needs more help that we can give it right now I'm Dan Reed thanks for watching drive safely too great hi I'm Dan Reid with the Community College of Philadelphia welcome to car corner left normal intro that sounds okay and by 8:15 mi-8 59 minutes yet okay I did this valve open on the side I'm gonna do this I'm gonna I'm going to present here and I'll just print rapper Fetty here yeah let me try don't go like this yeah stop move over ah you

Channel: CCPTV53

Views: 138,167

Rating: 4.8168573 out of 5

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Id: 6O6Jzrj5HDs

Length: 59min 12sec (3552 seconds)

Published: Tue Sep 17 2013