7 Common Symptoms of a Bad or Failing Thermostat

so if you have a vehicle that's having problems it's overheating or something like that and you think it might be the thermostat I thought I'd go over seven common symptoms of a bad or failing thermostat and how you go about telling if it is the thermostat or not and what are some common symptoms well there could be high temperature readings because the engine's overheating the engine might not be heating up at all when the weather's cold out the coolant fans can stay on constantly where they just stay on all the time they never shut off there could be erratic changes in the temperature so one minute it's cold and the next minute is overheating there could be unusual noises like gargling noises or something like that there might be coolant leaking out and so what is an engine thermostat well the engine thermostat is a pretty simple device it basically stays shut when the engine's cold and then as the engine warms up it'll start to open up and that is one way you could test these thermostat is that if you take it out and you stick it in hot water it'll open up and when it does that you know it's working right you could even put a thermometer in the water to see what the temperature is and the thermostat will have a rating on it like this one right here 180 degrees Fahrenheit and when the water hits that temperature it's going to open up and the thermostat's going to be located inside of a housing on the engine and when it opens it's going to let all that coolant flow past it go into the radiator the coolant to be cooled and then there'll be a hose down here at the bottom the coolant will flow back into the engine it'll cool the engine and it'll go into a cycle like this keeping the whole engine cool and that thermostat needs to stay closed when the engine's cold especially in cold weather so that it warms up if the weather is extremely cold and that thermostat's stuck open then the vehicle can never warm up and then it won't run its best and quite often the heater won't work in that kind of situation and so the thermostat is a simple device that just helps the engine warm up quickly and then it can also help to maintain the temperature and so the most common symptom when the thermostat goes bad is that it gets stuck closed and the engine starts to overheat and so the temperature gauge is going to go up as the engine warms up and then it's going to run too hot and then there's going to be overheating and when the engine overheats the fluid can bubble out it could come out to overflow on the radiator the reservoir can be low or go empty because all that fluid is going to blow out because it got hot and so the most common symptom is that the engine's overheating since that thermostat's still closed if the opposite happens if that thermostat stuck open all the time and especially if the weather is really cold out then the engine will never warm up since that thermostat's not blocking the flow of the coolant and so that can be the symptom is that the weather is really cold out and that engine won't warm up and it just stays cold all the time you go to turn on the heater and it's not working because that coolant isn't getting hot then the thermostat is probably stuck open it needs to be replaced another symptom when the thermostat goes bad when it's left closed is when the engine overheats is that these radiator coolant fans are just going to run all the time they're never going to stop and they quite often will be inside of high mode it's going to vary it's going to depend on the vehicle sometimes there'll be one fan sometimes there'll be two fans but if the radiator coolant fan it's just running all the time and it never shuts off and that is a sign that the engine's overheating and that that thermostat is stuck closed another sign when that thermostat's not working correctly is that sometimes it will open and then sometimes it'll close it'll do different things but it's not doing it at the right time and when that happens the engine can be hot and then it could be really cold and then it can be hot and then cold so if your temperature changes are erratic and just all over the place then that can't be a symptom that that thermostat has failed another symptoms you can hear unusual noises going on like gurgling noises or things like this and this is because the engine's overheating and the pressure's building up and that fluid is moving about inside of there so if you hear any noises like that like any kind of gurgling or hissing or things like that then that can't be a symptom that the thermostat has failed another possible symptom is that there could be coolant leaking out and again this is because it's overheating and when that happens the coolant can blow out the Overflow or things like this and so if there is coolant leaking out and it's overheating then that's a sign that the thermostat's failed and so what are some ways you could go about telling if the thermostat's failed how can you go about testing it well like I said before you can't take it out and stick it in hot water you can even see what the rated temperature it is set at to open and if you put a thermometer in there with it and check to see if it opens then that can tell you if it's failed or not of course these thermostats are low-cost devices so if you do take it out it's usually best to replace it with a new one but how would you go about testing it without taking it out well a common method to go about testing is usually a temperature gun and basically what you do is you start the engine up you warm it up and if that thermostat opens then the temperature should be the same on both sides of the housing or very close to each other so if you took a temperature reading before the thermostat housing then the temperature coming out the other side should be close to each other if the temperature before the thermostat housing is really high compared to after then that's a sign that is stuck closed because that coolant should be flowing through and so the temperature on both sides of the thermostat should be fairly close to the same but if it's much hotter over here than it is over here then you're going to get some big changes in your temperature readings and these temperature guns are fairly low cost items you get them like for like 20 30 on like Amazon or Ebay but that's a very common method to go about testing the thermostat while it's still in the vehicle there is an old school method that you go about testing these which I don't recommend but many mechanics will do is that basically they'll start up the engine to warm it up and then they'll squeeze this hose right here to see if any coolant is flowing through it because if you squeeze it real hard you should be able to feel the coolant coming through this hose if you don't feel any coolant coming through then you know that thermostat is stuck closed if you do feel it coming through then you know it's open I don't recommend this method because this hose can get very hot you could burn your hands so I would recommend using a temperature gun but many people do it but like I said I don't recommend that method and so that's basically it I just wanted to make a video on some common symptoms of a bad or family thermostat if you have anything to add please comment down below if you have any questions ask me and I'll try to answer them if this video helps you please click like please click subscribe and have a good day

Channel: HVAC Mechanic

Views: 183,589

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Id: SZ4121zceNQ

Length: 5min 19sec (319 seconds)

Published: Sat Jun 24 2023