How to Find and Fix Vacuum Leaks - Ultimate Guide

hey how's it going do it yourselfers today I'm going to show you what are some symptoms of a vacuum leak and also hike and find and fix any vacuum leak on your car alright so first things first vacuuming is any amount of on meter or unmeasured air that enters your engine as you may know your map sensor which stands for mass airflow sensor is the metering sensor that measures the amount of air that enters your engine and your computer uses the information received from this sensor to calculate the exact air fuel mixture necessary for running your engine under different conditions so that basically means has this sensor all your air hoses your vacuum lines or your intake manifold gaskets or any other type of vacuum line needs to be in good shape and airtight in other words any air that escapes into the system has this sensor is going to be considered a vacuum leak and if you have a vacuum leak that's going to throw off their fuel mixture causing your engine to have performance issues now those issues can vary depending on the size and some degree location of the vacuum leak as I want to show you so first let's start with a small vacuum leak symptoms of a small vacuum leaks are generally speaking either fluctuating rpm at idle or a high rpm at idle if your car has no symptoms and again I'm generalizing here but the main culprit is going to be all the different vacuum lines the small vacuum lines that are coming out of your intake manifold it's very common for these vacuum lines to get both dry and brittle then start developing cracks and then their leaks through these lines into your engine now this car doesn't have any vacuum leaks but I'm going to create a small one for you so you can see the symptoms for yourself so first I'm going to start the car and then pull a vacuum line so you guys can see the effect it has on the rpm now I'm do this on a warm engine but as you can see our idle speed is about 750 rpms so now on the engine side we're just going to pull one of these vacuum lines to cause a small vacuum leak and see the effect it has on the RPM and this vacuum line looks as good as any there yeah I hope you guys can tell but running a little rough the RPM is slower now your o2 sensors are stabilizing the system so there's too much air in the exhaust therefore your computer is not hiding whew and now it's smoothing out and actually in fact now the RPM is well it's higher than where we started all right so what happened there was that when the other vacuum the extra air that gets into the system throws up throws out the air fuel mixture and when your computer senses that through your o2 sensors telling it that there's too much air in the exhaust fumes that are coming out of the engine it puts more gas in there to once again bring the ratio back into balance and the more gas and more air you have your engines gotta run faster therefore you see the rise in rpm now I think I need to mention that whenever you're looking for small vacuum leaks like we had here you're generally going to notice this these leaks at when the engine is cold at idle because on warm engine as you saw your o2 sensors are going to help your computer to make adjustments the fuel air fuel mixture and being your rpm back to its normal range which was 750 for this car so you notice these vacuum leaks when the engine is cold because when the engine is called your computer only goes by the readings from your MAF sensor all right so next let's talk about the symptoms of a large vacuum leak so a large vacuum leak is usually again accompanied by a rough idle but a low idling car but furthermore you might have a hard time starting your car if the leak is in the right place and it's big enough you may not be able to start your car at all but besides that you're also going to have a heart time to get your car going from a dead stop you might feel it hesitating or bogging down as you're trying to get going from a dead stop all those are symptoms of a rather large I can be and if you speak the large vacuum leak or have those symptoms I would start off by checking this air hose this air hole just like the vacuum lines gets old dry and brittle and starts breaking apart and I've seen it break apart right in between these areas where it's very hard to see where the times underneath it where it's easy to miss now the other culprit for a vacuum leak with no symptoms is your intake manifold gaskets either upper or lower intake manifold gaskets if your course has done now in the middle so if I can exactly find all these different vacuum leaks but for now let's cause a large vacuum leak on this guy and see how it goes and for a large vacuum leak I've already used in this clamp so I'm just going to pull this air hose out and simulate the condition of a large Mattingly CRO CRO fire engine is running it's almost going to die if I pull it out further and this large of a leak doesn't matter you owe it to censor tell your computers too much air in the system it just can't compensate for that you can also hear the hiss of the leak - and if I pull this completely out I can even kill the engine - all right well next let me show you what are some things that I do your solver can do in order to pinpoint the vacuuming all right one way to find a vacuum leak is to use some propane and the way this works is you open the regulator allowing propane to come out of the tank and then without lighting your propane torch obviously you start going to run all the areas or the suspected areas that you could have the vacuum leak you start after your map sensor you can go around the city main air hose then go to your throttle body gasket all the vacuum lines around your intake manifold and throttle body and then around your intake manifold gaskets and you want to be slow and methodical with this and cover all your bases again all the vacuum lines also don't forget around your fuel injectors if you can reach them and whatever area notice the difference in the RPM that's where your vacuum leak is that's because as you may know propane is combustible and when you list your engine through your vacuum leak it's going to affect your rpm and you're going to notice it this may seem dangerous to some people but this is actually safer than the next method I about to show you which is to use starting fluid to find a vacuum leak and a danger in using these is that let's say you have a bark from one of your spark plug wires or your ignition coils and you get this near that arc and that arc or spark causes a fire if it's propane you know you're just going to be a just one maybe ball of fire if your face is really close to it you might lose your eyebrows and stuff but if it's a starting fluid then it's a liquid it's going to catch on fire and you might catch your engine on fire and then please forget out of hand where you go so what method you use make sure you have one of these and/or a garden hose nearby and like I said the next method is to use starting fluid instead of propane when you starting for it make sure you use this on a cold engine because not all these orcs can catch this on fire but also the heat from your exhaust manifold if the car is already warm and you spray this in one area soak whatever component you suspect as the leak wait a little bit wait a few seconds if there's no changes to the RPM then you will move on to the next component or next vacuum hose or whatever now there are a couple of components that could cause a vacuum leak that starting fluid or propane can pinpoint and those are your brake booster your PCV valve and your EGR valve if your brake booster develops a leak you know no matter how much propane or sorry fold you spray around it you're not going to notice the difference because it's inside that component you can't get that stuff inside your brake booster all right so here's a look at our brake booster and here's the vacuum line that goes from our intake manifold to our brake booster now this line if you spray starting fluid around it or propane keep get propane close to it if it has a crack then you'll notice a difference but if the brake booster itself is has a leak inside then you won't know but the way you can determine whether this is a problem or not is after you test this vacuum hose that goes from your intake manifold to it use the pair of locking pliers and pinch this vacuum hose and take your brake booster out of the system if your rpm goes back to normal or your engine starts running better then you know there's a leak inside the brake booster and it's very much the same thing for your PCV valve if the valve is stuck open because it's going to cause a vacuum leak at idle and propane nor starter fluid is going to tell you whether that valve is stuck open or not but the way you can find out is after you test this vacuum hose do the same thing use a pair of pliers you pinch this hose if your RPM improves then more than likely that valve is stuck open causing your vacuum leak now if you want to learn a little bit more about the PC and how that works I recently made a video showing you how you can exactly test it at how the PCV valve and system work and I'll link to that video right here on this side of the screen where you can click on and it's very much the same thing for your EGR valve if this valve gets stuck open due to either carbon buildup or it simply fails in that position then you're going to have a vacuum leak here now diagnose the problem through EGR valve or EGR system as a whole is a little more complicated but again if you're not I have another video on that one as well and pulley to that one on this side of the screen too but both EGR valve and the PCV valve generally fail in the closed position now sometimes again they fail in the open position causing you to have a vacuum leak and if you speak the vacuum leak and you've done everything else and you can't find it then I will recommend you go to those two valves and check them for vacuum this that's all there is to it folks that's my version of how to find a vacuum leak on your car and if you find anything useful in this video please give it a thumbs up subscribe if you want to see more like it and also consider checking out some of my other videos I'll put up on the screen as video links so you can just click on it alright thanks for watching you

Channel: Ratchets And Wrenches

Views: 1,804,294

Rating: 4.8858514 out of 5

Keywords: Ratchetsand Wrenches, idle problem, won't idle, rough idle, stalls, idle, idle problems, bad idle, car won't idle, truck won't idle, vacuum leak, intake leak, finding intake leak, intake vacuum, intake vacuum leak, how to repair, diagnosis, automotive diagnosis, engine diagnosis, performance, performance problem, truck repair, engine repair, engine, rough engine, diy, diy car repair, diy auto repair, automotive education, P0171, EGR, PCV, Power Brake Booster, Valve

Id: qTzDY95aqXg

Length: 10min 42sec (642 seconds)

Published: Sun Oct 18 2015