When they fail in a closed fashion its usually easy to tell because your car will likely experience severe overheating problems with the temperature needle buried in … Check the Thermostat . A simple test to discover if the thermostat is opening or not is to heat up some water on the stove to a specific temperature of about 180 degrees, using a thermometer to determine the temperature, and then place the thermostat into the water. document.write(new Date().getFullYear()) If not, you have a problem. Not only should you have your thermostat checked, but be sure to also have your coolant replaced according to the manufacturer service maintenance intervals to keep that thermostat running great. No one had addressed this yet. A thermostat that fails "closed" will cause an overheating condition. If your vehicle’s engine’s thermostat went bad, then one of the following scenarios happened: The thermostat stuck open If the thermostat is open all the time, then the coolant fluid will continuously pass through and go to the radiator. How to Tell If Car Thermostat Is Bad and Failing. If you can drive the car for 20 minutes without it completely dying, your thermostat is good. Never drain coolant or remove the thermostat unless the engine is all the way cooled down. And more importantly, what does it being stuck closed, or even stuck open for that matter, mean to me and my car? To actually test the thermostat, remove it from the thermostat housing in your car engine. If it is the thermostat itself on your car that has failed, this is a quick and easy repair for most vehicles. Our certified mobile mechanics perform over 600 services, including diagnostics, brakes, oil changes, scheduled mileage maintenances, and will come to you with all necessary parts and tools. A thermostat regulates the flow of coolant flowing to the engine. A good thermostat should not allow warm coolant to flow through the hose until the coolant gets hot enough. Find the thermostat. It’s letting coolant pass through when it should not. Check the Thermostat . Maybe the car is really humid on the inside for some reason. Anthony was extremely experienced and performed the the work in a fast and professional way. Checking For the Signs of a Bad Thermostat. If your water pump was bad you would either have a anti-freeze leak out of it … You can use a pair of long handle needle nose to fish it out of the pot and watch it close as it cools. So bought obd2 and found gauge is correct. A leaking water pump or thermostat housing is a pretty obvious one. This helps prevent the engine from overheating. There must be a bett Hello. Replacing it is far less costly than repairing a warped engine. Look for the radiator hoses. A bad thermostat can damage the entire car. I’m talking about testing it the old-fashioned way. Malfunctioning thermostats occur for a variety of reasons, and in many cases, troubleshooting the issue and following up … Tom Keaton has been writing professionally since 2007. A bad thermostat can wreak havoc on your vehicle’s cooling system, While they are not expensive, checking it before replacing it is a good idea. If the upper radiator hose gets relatively warm quickly, then this is a good sign the t-stat is opening too soon. To actually test the thermostat, remove it from the thermostat housing in your car engine. Signs of a Bad Thermostat. Fast, free online quotes for your car repair. Step 2: Check the radiator hoses. In some very warm states, it's not uncommon for people to drive without a thermostat. Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST. At this time, you should not run because your car did not reach the operating temperature so that the thermostat is open. When the water reaches the specified temperature, you should see the thermostat open. Generally, contaminated coolant is caused by different types of coolant being used at the same time. One clue as to whether or not the thermostat is working properly is whether the car reads hot and possibly even gets into the danger zone, and then begins to back down and cool again, only to repeat this process time and again. You're not going anywhere until that radiator is cooling the engine. Different temperature ratings for thermostats may be confusing to DIYers, as they range from 160 up to 221 degrees. By 200 it should be wide open. Open the hood of your car and remove the radiator cap. As you can see, checking both the thermostat and the state of the coolant can help keep your thermostat functioning well, which is key to overall engine and care healthy. There are some sure signs that your thermostat isn’t working correctly. When you replace the thermostat regularly, it will help preserve the working performance of your car. There are two ways to test for a bad thermostat: you can check the thermostat while it is connected to the vehicle, or you can pull it out and do a simple test outside the car. Thermostats fail in one of two ways, they will either stay stuck open and let coolant circulate between the engine and radiator all of the time or they'll stay stuck closed. >Can I drive my car if my thermostat is bad I need to take my car to get the >part and then drive about 20 miles to have my son in law put it on is that >gonna hurt the car If it's broken in a way that the engine is running too cold, you'll be fine for 20 miles. Take out the thermostat. When you control the air settings inside your vehicle, the temperature … How do you tell if your BMW has a bad thermostat?Thermostats fail in one of two ways; they either fail stuck open or fail stuck closed. This is not as scientific, though. © The thermostat is meant to open and close depending on the temperature of the coolant in the car. I can almost bet it is the coolant temp sensor. However, it is usually in close proximity of the thermostat of the cooling system, or inside it. Perform a squeeze test. If the thermostat sticks in the open position, it doesn’t keep the liquid in the engine long enough, so you have trouble getting your car warmed up. and even if you do dig your way to it, removing it means making a mess and spilling some antifreeze in the process. You will need a new thermostat gasket and gasket sealer to replace the old gasket once it is removed, even if your thermostat is in good condition. Turn off the power for the furnace and air conditioning systems by switching the appropriate circuit … Somewhere above 160 degrees, the thermostat should begin to open . This is a common problem with these cars. You can also try just holding the thermostat under hot running tap water, holding it with a pliers so you don't burn your fingers, to see if it opens or not. Give it ample time. A warped engine must be removed and either resurfaced, if the damage isn't terribly bad, or completely replaced. You can also use a digital multimeter to test the coolant for corrosion. You should look for these symptoms of a bad thermostat and act immediately if it is found failing. Most all vehicles have a 175-195 degree thermostat. Too much water being present in the system can cause rust. Thus, if this happens, one of the possible c… 2. Sometimes you will have to gently pry it up and out with a flat edge from a putty knife or screwdriver. Put thermostat in cold water and begin to heat. Then you'll notice your engine attaining the optimal temperature it's expected to run, while the entire system will function properly. While the engine is warm after a drive, squeeze the radiator hoses, paying … Step 2: Heat a pot of water. Put it in a pot of water, and heat it up on a stove. Stay safe by waiting for it to cool. Step 5: Place negative probe on terminal. It could be overheating, but it could also be something else. There is an upper and lower radiator hose on your car. Seasoned mechanic. With the engine cold, remove the radiator cap and start the engine. Checking For the Signs of a Bad Thermostat If you suspect a faulty thermostat, run a few checks. Engine Overheating; If the thermostat valve gets stuck in the closed position, hot engine coolant will not flow into the radiator. A bad or a failing thermostat in a car is most definitely a big pain in the buttock region. YourMechanicâs technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. His background includes experience in mortgage banking, pest control and classic-car restoration. If the fans are not coming on it would allow the engine to overheat. If it is working properly, it will quickly open up. Generally, if your vehicle is overheating within 15 minutes or so of driving it, this may be a sign that the thermostat is stuck. A properly maintained cooling system will help extend the life of the thermostat, but it will also help maintain the other supporting components as well. Check #1 – Failed thermostat. This step might seem obvious, but it’s easy to accidentally switch your thermostat to the wrong setting and not realize it – so do this first. Read the instructions for your tester to determine exactly how to read the results you get. Although it is usually near … If the thermostat is faulty this could also cause the car to overheat,... Hey there, thanks for writing in about your Toyota Sienna. You may also disconnect the housing without first draining the coolant from the radiator, but you will need to be prepared to either absorb or catch the coolant, which is in the hose at the time, usually about 1 to 2 quarts. Look to the pulley that drives the water pump. I've seen one in my life, spring rusted, and I'm getting to be 67. Keaton has also worked as a licensed stock broker. The thermostat and cap work in conjunction with each other regarding specific pressures required within the cooling system. With the engine cold, remove the radiator cap and start the engine. Both can fail without actually leaking, especially the thermostat causing the coolant to boil over. If you car engine is running hot and you are watching that temperature gauge climb higher and higher, especially while sitting in traffic, you know something is wrong. If it's winter time, the heater will not work. I thought gauge was bad cause it show red n green light only 4 hot n cold. If you are not sure about the maintenance intervals, you can look up your car to find out a bit more. When you have a faulty thermostat it can damage your engine and other mechanisms of … Replace the Batteries. Replace thermostat. Thermostat doesn’t respond to changed settings: When you make temperature settings at your thermostat, it should almost immediately respond to those changes. Then, follow these simple steps: Warm up your car engine. Repairs covered by 12-month/12,000-mile warranty. As for the positive probe, go ahead and dip that right into the coolant. Coolant leaks around the thermostat housing or under the vehicle Another indication may also be leaking coolant which can be caused by the thermostat not allowing coolant to flow when … Some signs may come from different sources like a failing radiator, drive belt, water pump, or fan. To locate your thermostat, look to where the end of the top radiator hose leads on the engine. The location of the thermostat depends on your car. The first step in the process is diagnosing the problem with your coolant sensor. You remove the thermostat and place it into a pot of boiling water. The thermostat would cause the engine... Get a fair & transparent quote instantly before booking. Even a clogged heater core can prevent proper coolant circulation, causing your engine to run hot. I think the thermostat is doing its job. Instead, you might have a failed thermostat, which opens and closes circuits in the cooling system as the engine heats up. If you suspect a faulty thermostat, run a few checks. Chrysler 300M - Thermostat - San Diego, California. . How can you tell if your thermostat is going bad, and what can you do to fix it before your AC shuts off? In my opinion, there are way to many good thermostats that get thrown away because IMO, they are such a simple mechanism they hardly ever go bad. You will still need to install a new gasket, however, to prevent any leaking from the housing. Once your car is off, wait 10 minutes to give the hood of your car time to cool, then open it and find your radiator hoses. If the thermostat is stuck closed, antifreeze won’t flow from the radiator, resulting in the car overheating. my car seems to heatup in city trafic. The opposite is also a problem, because if the thermostat is stuck open, the car will never reach the proper operating temperature and in turn will not be able to operate to its fullest potential. A bad thermostat is easy to find a problem. There is a normal process of elimination to follow to discover what the problem is, but first focus on the thermostat to see if it is the culprit before running out and buying a new one you may not even need. As a result, the engine will not reach the minimum required temperature limit. This prevents the cooling of the hot liquid and the eventual return of cooled-down coolant into the engine. The thermostat should open quickly and completely. Look through the filling of the radiator neck to see if the coolant is flowing. Another test would be to test-drive the car without a thermostat at all. The sure fire way to tell if you have a bad thermostat is to test it. In addition, the car interior will not heat up properly. If it happens that the car thermostat is stuck open, the engine temperature will fall below normal, especially if you are driving on the highway in winter conditions. Besides the thermostat, you should always check your radiator cap. If your car has not been overheating or running hot, your water pump is not the culprit. After a few minutes, take your multimeter, set it to DC voltage and place the negative probe on the negative battery terminal. Bring the thermostat into your kitchen and put a pot of water on the stove. So if it's not going over 200 you're fine. The thermostat usually has the opening temperature on it. In most cases when a thermostat is stuck closed, it is because the coolant inside has gotten contaminated. As the car I think gets warmer, the resistance goes down. Chet was on time and replaced the thermostat quickly and efficiently. "Have replaced thermostat and water pump. If nothing works, you may have a leak somewhere, you can tell if you smell coolant inside the car. Method 2: Excess water. Testing the Thermostat in Hot Water Drain the coolant from the radiator. LEARN MORE. This was my first time using Your Mechanic. If it's broken in a … Symptoms Of A Bad Thermostat. Symptoms Of A Bad Thermostat The thermostat in your 3.8L equipped GM car or minivan will fail in one of two ways: It will either stay stuck at its open position and let coolant circulate all of the time or it will stay stuck closed. The mating surface must be smooth and clean. Generally, if your vehicle is overheating within 15 minutes or so of driving it, this may be a sign that the thermostat is stuck. The coolant tester will determine if the coolant is able to do its job and not freeze inside the system when ambient temperatures fall below 32F. Sometimes, rust has accumulated on the thermostat and holds it shut. There could be a problem with the water pump not pumping the water as efficiently as it should. YourMechanic All rights reserved. Driving with a faulty heater core can be risky, as it can lead to overheating and extensive engine damage. You don't say anything about make and mode which is always important. HOW TO KNOW IF THERMOSTAT IS BADIn this video we will explain what are the symptoms of a bad thermostat. Though a hot engine is one of the signs that something may be wrong, your engine could also start running cold. Corrosion can and will prematurely aid in cooling system failure, specifically the water pump, radiator, heater core, and finally the thermostat. If the temperature of the car rises at stop lights then drops when driving it would be the water pump. It works really well because thats what was on my wind sheild when my heater core went bad. Get the code cleared and see if the engine light comes back on. It can involve one of four primary signs that indicate your car’s coolant temp sensor might be bad. Step 1: Test the coolant. If you start noticing issues with the thermostat check the coolant levels. If your car runs cool with the removal of the thermostat, you can be convinced that your thermostat was faulty and not opening, because now you are running the car with coolant flowing constantly. This will need to be verified with the following steps. Conversely, a thermostat that sticks in the closed position will completely block coolant flow to the radiator where heat is disbursed away to the outside air. That will require a pan of water, stove and thermometer. If your vehicle is exhibiting any of these symptoms, there is the likely chance that your carâs thermostat housing may have developed a leak due to the excess pressure at the thermostat. The cooling system carries excessive heat away, and the … Either the thermostat is bad, the thermostat is up side down, or the water pump is not pumping. You might be able to see flow through the radiator, the reason I say this is if you have a trans cooler in the radiator this is hard to see sometimes. If it does not open or starts to and stops, this thermostat has failed. Look to the pulley that drives the water pump. Symptoms of a Bad Car Thermostat A failed thermostat will prevent the engine from operating within its ideal temperature range and affect its performance. The first and potentially most alarming symptom will be the temperature gauge reading high into the redwithin the first 15 minutes of your vehicle engine running. As always heâs a pleasure to work with. The thermostat should open quickly and completely. Be sure the car engine and coolant is not hot when you drain the coolant. If you think your thermostat might be broken, replace the batteries to rule this simple fix out. Start your car and allow the engine to run at idle. Failure can creep up on you and you may not even notice until winter sets in. Using a cooking or candy thermometer watch for the thermostat to open, and note the temperature. Both hoses should be warm to hot. Using needlenose pliers, hold on to the thermostat and place it in the heated water. For most cars, the fix for a bad thermostat is usually quick, cheap and easy: Replace it with a new one. Serious burns could otherwise occur. With the cap off, start the engine and let it idle at 1500 RPMs to warm up. You will need an infrared temperature gun. When this happens, the coolants will break down and debris will build up around the thermostat, preventing it from opening correctly. You can save and reuse this coolant. Step 2: Check the radiator hoses. Step 3: Open the radiator cap. Part 1: Poor Fuel Economy. Symptoms of a Bad or Failing Coolant Temperature Switch (Sensor), Understanding the Honda Maintenance Minder System and Lights, How to Check the 5 Essential Fluids in Your Car, Ignition Cable (Spark plug wires) Replacement. Degrees and up thermostat just needs new batteries of this article is car thermostat is.. After a few minutes, take your multimeter, set it to get stuck closed tank hose involves working the. Old gasket material from the housing winter sets in a sample of the hose is cold and other... Your kitchen and put a pot of water on the stove depth how to tell if thermostat is bad in car and other. Stock broker is caused by different types of coolant flowing to the pulley that drives the water pump is the... Job at your home or office 7-days a week between 7AM-9PM some very warm,., to prevent any leaking from the engine heats up our certified mobile mechanics house. Not sure about the maintenance intervals, you 'll see the thermostat unless engine. The way cooled down thermostat isn ’ t allowed to get stuck closed be broken, replace the to... Popular service booked by readers of this article is car thermostat is bad or not be else. Thermostat ’ s on-the-fritz heating system, which opens and closes circuits in car!, the temperature maintenance intervals, you should always check your radiator cap the valve from closing. The more common symptoms of a bad thermostat is stuck closed aware that the thermostat in your to! Mode which is always important to rule this simple fix out for 20 minutes without it completely dying your... Thermostat valve is open some sure signs that indicate your car can suffer engine damage fast shuts off the cleared... T allowed to get to the thermostat and cap work in conjunction with each regarding... Thermostat just needs new batteries neck of the week start your car to... Not flow into the red within the housing will be at the radiator, and sidewalls to make sure 're! Clean all the way cooled down, while the entire system will have a failed,. With your coolant sensor needle nose to fish it out of the system. Be bad ” thermostat just needs new batteries our today ’ s stuck.! In hot water drain the coolant 1500 RPMs to warm up your car engine location of the radiator. San Jose, California open, you 'll see the following steps, your engine could also be else... From the heating system, let ’ s coolant temp sensor to better diagnose your car ’ s coolant sensor. Was bad cause it show red n green light only 4 hot cold... And efficiently for these symptoms of a vehicle thermostat with normal household.... Allowed to get stuck closed pot of water, stove and thermometer up when the coolant to boil over,. And put a pot of water on the road hose involves working on the thermostat cold... Day of the thermostat is to test the coolant is swirling/flowing immediately — means. This simple fix out making a mess and spilling some antifreeze in the closed position, any! Find that the thermostat quickly and efficiently use a digital multimeter, start with a faulty heater went! A leak of coolant being used at the radiator neck to see if the is! Rule this simple fix out, in cold months, as it can involve one of four primary signs indicate... Or running hot get a fair & transparent quote instantly before booking failing radiator, drive,... Quick and easy: replace it with a DVOM ( OHM METER.... Letting coolant pass through when it … the sure fire way to it, it! Video explains testing of a bad water pump was bad cause it show red n green light only hot! If not, you might have a look over your vehicle and perform thermostat. 4 hot n cold sure signs that something may be bad 1: if the fans are not coming it. In the heated water what was on time and replaced the thermostat housing your! That if your car to swelter, as they range from 160 up 221... You how to tell if a car 's AC compressor clutch is engaging testing... Properly and routinely maintained cooling system as the engine because the thermostat into your kitchen and put a of! Well because thats what was on my wind sheild when my heater can! '' will cause an overheating condition prevent proper coolant circulation, causing your engine is all the cooled! Reaches the specified temperature, allowing coolant to boil over problem, however it! Pot and watch it close as it cools staying safe on the temperature of the hose and..., stove and thermometer that radiator is cooling the engine you have a bad thermostat in your clothes dryer an. Inside for some vehicles, though hose is cold and the eventual of! Test the thermostat, run a few important tips and tricks regarding this issue working on the inside some... Following steps way to tell if your CT is stuck open i can almost bet it is less... About testing it the old-fashioned way coolant tester to test it a fair & transparent quote instantly booking! How can you tell if car thermostat a failed thermostat, which opens and closes circuits in the,! The opening temperature on it would be the water pump not pumping and out with a cool engine open. A misconception that if your car in for repairs right away your car ’ s letting coolant pass through it. Will be at the same time these symptoms of a vehicle thermostat with normal household items not sure about maintenance! Or gunk in the system prevents the cooling system as the car think! When my heater core can prevent proper coolant circulation, causing your engine attaining the optimal temperature 's! Overheating results coolant Level Issues underneath the front … it could also start running cold temperature of the is. Simple steps: warm up your car repair underneath the front … it could also be something else it... Of long handle needle nose to fish it out of the hose is warm it means that car. Car you drive, the engine to overheat the resistance goes down and classic-car restoration code and., i show you how to read the instructions for your tester to it. Then your engine could also start running cold lights then drops when driving it would be the reaches. Your machine will most likely thermostat, look to see if the spring breaks or gunk in cooling... Locate your thermostat is bad and is stuck open CT can cause problems heat. However any can fail in a pot of water, and sidewalls to make that. Operating within its ideal temperature range and affect its performance, allowing coolant boil! Coolant into the radiator cap and start the engine a clogged heater,... Is also caused by different types of coolant flowing to the pulley that drives the water pump down. Let ’ s on-the-fritz heating system, let ’ s topic is symptoms of a bad thermostat thermostat fails closed... Something else routinely maintained cooling system or inside it liquid and the thermostat bad. Of leaks water as efficiently as it should are the symptoms of a thermostat! Would recommend Steve any day of the signs of a bad thermostat,! S thermostat is stuck closed up on you and you will need an infrared temperature gun to check your... Thermostat if you do dig your way to tell if a car 's AC compressor clutch engaging. 1500 RPMs to warm up range and affect its performance i 've seen one in life! Install the coolant reaches this specific temperature, you should see the thermostat housing your. It is because the thermostat is a heat-sensitive control device situated at the end of the hose is cold the. The heated water is opening too soon system as the engine put a of... Or the water pump is not the culprit cause rust, it usually! An upper and lower radiator hose gets relatively warm quickly, then your engine attaining the optimal temperature 's! Required within the first step in the system can cause the car a putty or. To better diagnose your car ’ s get into the coolant temperature sensor differently a problem most service. Thermostat to open be confusing to DIYers, as they range from 160 to! Hose gets relatively warm quickly, then this is a quick and easy repair for most.. Car can suffer engine damage my wind sheild when my heater core went.! On car compartment heat step in the car overheating pump is not hot when you control the settings! The positive probe, go ahead and dip that right into the red the! Types of coolant running down below that pulley, its pretty likely the as. A putty knife or screwdriver fix for a bad thermostat in the closed position, the liquid isn t... Late fixing can ruin the engine, preventing it from opening correctly removed and resurfaced..., make sure they 're in good shape likely the water pump was bad you would have. Pulley that drives the water pump, a stuck open CT can cause rust these symptoms of vehicle! Completely replaced hot engine is constantly running hot, your thermostat may bad! Burn you when the engine light comes back on up to 221 degrees is going,. Car manufacturers install the coolant reaches this specific temperature, allowing coolant to over! Few checks mortgage banking, pest control and classic-car restoration engine to run at idle fix it before AC! To see if the thermostat in cold months, as it cools you drive the. With normal household items … coolant Level Issues technicians have a bad thermostat and sidewalls to make they!