Dan Ferrell writes around do-it-yourself vehicle maintenance and also repair. He has certifications in automation and also control technology.

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Car thermostat troubles happen unexpectedly. Usually, you'll begin to notification that your vehicle begins come overheat shortly after you fire up the engine, or the temperature gauge on her dashboard remains below its normal temperature point.

But how do you recognize it is the thermostat acting up? ~ all, few of these exact same symptoms might come native a failing water pump, radiator, fan, or also a loose drive belt.

In general, as soon as a thermostat offers out, it it s okay stuck in a closed or opened position. Everything its failing state, you'll discover out in a couple of minutes using one or much more of the tests explained in this guide. Yet first, you must take a rapid look at exactly how it operates so the you recognize the logic behind these an easy tests.


What walk a vehicle Thermostat Do?

The Thermostat in ~ Work

Bad auto Thermostat Symptoms

Common reasons for Abnormal Engine Temperature

How carry out I understand If My automobile Needs a Thermostat?

Checking Coolant Flow

Checking Coolant Temperature

How to test a auto Thermostat


What does a automobile Thermostat Do?

As any type of other water-cooled engine on a passenger vehicle, the engine in your car operates in ~ a temperature range of approximately 195–220 °F (91–104 ºC). To help it operate within this range, your auto engine provides a thermostat.

In simple terms, the thermostat responds to changes in temperature—in this case, coolant temperature—by opening or closing a valve to regulate coolant flow between the radiator and engine. The valve itself operates through a wax-container element. Thus, the thermostat is small, basic and effective. The expanding element container in the thermostat faces and also contacts the engine coolant. Together the coolant temperature rises, the liquid (or wax) in the container starts to melt and expand, advertise a small rod the separates a facility plate indigenous its bordering mounting base to open up the valve.

The Thermostat in ~ Work

The thermostat starts in ~ a close up door position when you begin the engine to aid it reach operating temperature. Together coolant temperature rises, it starts to open. The opening allows hot coolant in the engine to circulation into the radiator, while the water pump pushes lower-temperature coolant from the radiator right into the engine. Once the lower-temperature coolant get the thermostat container, the expanding fluid starts to contract, closing the thermostat's valve.

During engine operation, though, the thermostat actually never totally closes or opens, yet gradually nears either state to manage coolant flow, depending upon engine operating conditions. This permit the engine to run at the ideal temperature. This ideal engine-operating temperature accomplishes numerous goals: It help engine oil come lubricate efficiently and to eliminate harmful deposits. That reduces emissions and gas consumption, and also contributes to engine performance. Thus, the thermostat has an influence on her engine's health and also longevity.

Symptoms of a Bad car Thermostat

A fail thermostat will avoid the engine from operating within its appropriate temperature variety and impact its performance. For example:

A thermostat stuck opened up will cause a consistent flow the coolant, causing a lower operating temperature. Because the oil operates below temperature, the condition accelerates parts' wear, reducing engine efficiency and also increasing emissions end time.On the various other hand, a thermostat stuck in the closed position will protect against coolant flow and also cause the temperature to stability rise. If you fail to an alert and keep your engine running, in a matter of minutes your engine self-destructs. Literally.

Either way, her engine will suffer damage. The distinction is just in the amount of time it takes. Still, a failing thermostat is no the only cause for an abnormal engine operation temperature.

Other reasons include low coolant level, a poor water pump, a worn out or loosened water pump belt, cooling device leaks, a clogged radiator, a fail radiator fan and a fell down radiator hose. Whatever the cause, it's a an excellent idea to begin looking right into the problem prior to it's as well late.

Common causes of Abnormal Engine Temperatures

Bad thermostatLow coolant levelBad water pumpWorn-out water pump beltLoose water pump beltCooling system leaksClogged radiatorBad radiator fanCollapsed radiator hose


How carry out I understand If My car Needs a Thermostat?

Now that you have actually an idea of just how the thermostat operates, you have the right to use that knowledge to inspection the problem.

First, open up the hood and also make certain the engine and also radiator are cool.Then, situate the thermostat. If you follow the top radiator hose towards the engine, you will check out the end of this hose connecting to the thermostat housing. Within this real estate resides the thermostat. ~ above some automobile models, though, the thermostat housing connects to the reduced radiator hose.If you need aid to find the thermostat, top your car service manual. You have the right to buy one in ~ your regional auto parts store or online. You could likewise check the referral section of your public library.Once you've uncovered the thermostat, perform one of two basic tests: If girlfriend have accessibility to the radiator cap on her car, use the adhering to troubleshooting procedure: check Coolant Flow. If the radiator cap is no accessible, or you don't check out the cap, go to the following troubleshooting procedure: check Coolant Temperature.

Some Recommendations prior to You Start:

Even if her radiator cap is accessible, you can actually execute both tests, due to the fact that neither calls for removing the thermostat from your car and also they both just take a couple of minutes.

With an overheating engine problem, it's a an excellent idea to have actually an assistant behind the wheel come shut off the engine if the temperature get an unsafe level while testing.

If one of two people of her tests points come a bad thermostat, monitor up v the 3rd procedure below, how Do ns Test a vehicle Thermostat, to check it outside of the vehicle and also make sure you must replace it.

If you space performing one of these tests due to the fact that your engine is overheating, it's a great idea to have an assistant behind the wheel to shut off the engine if the temperature will an unsafe level while you do the test.

How to examine Coolant Flow

Wait for the radiator and engine come cool.Engage the parking brake and block the wheels.Remove the radiator cap, fire up the engine and also let the idle.Verify the the coolant is not flowing. Girlfriend can check this by looking with the radiator filler neck. The coolant shouldn't be flowing since the coolant has not reached sufficient temperature to reason the thermostat come open.If the coolant is not flowing, walk to action 7.Wait for around 10 to 20 minute so the engine reaches operating temperature. About this time, you'll check out the coolant through the radiator filler neck start to flow. The coolant starts to circulation at this suggest because it has actually reached a high sufficient temperature to reason the thermostat come open.If friend don't see the coolant flowing and the temperature gauge on her dashboard is increasing steadily, you have actually a thermostat stuck in the close up door position. Shut turn off the engine and also refer to the section, after ~ the next procedure, just how Do i Test a vehicle Thermostat.However, if the coolant begins to flow but the engine still overheats, girlfriend have another problem affecting the cooling system. Examine the troubleshooting section of your vehicle repair manual to check out other causes for engines overheating.


How to check Coolant Temperature

A simple way to check for coolant temperature, and hence, thermostat operation, is to use your own hands.

Engage the parking brake and collection your transmission to Neutral (manual) or Park (automatic).Start the engine and also let that idle.Touch the top radiator hose and also lower radiator hose, so that you have the right to feel the hoses' temperature. Be careful with engine moving parts when doing this.Wait about 10 minutes and repeat step 3. Girlfriend should notice the hoses' have risen in temperature. This method the thermostat is opening. If the hoses' temperature have actually remained about the same, the thermostat is stuck closed.

If girlfriend want, you deserve to do a much more accurate test. For this test, you deserve to use a needle type, kitchen thermometer or an infrared thermometer type.

Make certain the radiator and engine are cool, connect the parking brake and also block the wheels.Start the engine and let the idle.Get a temperature reading on the engine block or cylinder head surface near the thermostat housing. Then, obtain a temperature reading of the upper radiator hose two to 3 inches far from the thermostat housing.After five minutes, check out the temperature again top top these same two test points and also compare this readings come the ahead ones.Wait because that five much more minutes and also take one more reading.At this time, you'll begin to notice the temperature on the engine block or cylinder head rising while the radiator hose temperature remains about the same.

Interpreting her results:

If both check points stay at around the same low temperature, your vehicle thermostat is grounding opened. This means the coolant is flow continuously, maintaining the engine from getting to operating temperature. This will certainly confirm the continuously low temperature reading of the temperature gauge on your dashboard. Change the thermostat.It takes between 15 and 20 minutes because that the engine to reach operation temperature. In ~ this time, hot coolant reasons the thermostat to open. If girlfriend take another temperature reading on your 2 test points, you'll notification the radiator water tap temperature virtually as high as the engine’s temperature. This means the thermostat has opened and also hot coolant is flowing with the radiator hose.If coolant doesn't flow, you'll notice the temperature ~ above the upper radiator hose remaining around the same, and also the temperature gauge on her dashboard obtaining close to the red zone. This way you have actually a stuck closed thermostat.If necessary, troubleshoot the thermostat as explained in the next section.If the temperature on the upper radiator water tap rises, though, coolant is flowing. If her engine is still overheating, friend have one more problem affecting the cooling system. Inspect the troubleshooting section of your vehicle repair manual to view other causes that might be affect the cooling system.


How to test a vehicle Thermostat

Checking your vehicle thermostat is the best means to know if the unit has actually actually failed. The experimentation procedure requires a kitchen thermostat and also a pair of needle nose pliers. First, you need to remove the thermostat from her car.

The thermostat housing is easily accessible in many cars, however you still should follow part precautions that might use to your specific model. If you need much more help, the best way is to follow the accuse in the repair hands-on for your certain vehicle make and model.

Once you have removed the thermostat from your car:

Visually check the thermostat. It should be in the closeup of the door position. If the is opened, replace it.Place a kitchen pot on a stove. Pour enough water right into the pot come cover the thermostat.Submerge the thermostat in the kitchen pot, but don't let the touch the bottom that the pot. Use a pair the needle sleep pliers because that this.Start heater the water and also place the kitchen thermostat in the pot, but don't permit the thermostat come touch the pot. You just want to monitor the water's temperature.Watch very closely and an alert at what temperature the thermostat starts to open.Make a note of the temperature in ~ which your thermostat began to open.Wait for the thermostat to open totally and make a note of the temperature. Then, eliminate the thermostat indigenous the pot and check the the thermostat progressively closes completely.Compare your notes come the thermostat operation temperature specifications in your automobile repair manual. If your thermostat deviates from the specifications, or the thermostat mechanical activity deviates from the one described above, change it.

Most vehicle engines run at a temperature range of roughly 195–220 ºF (91–104 ºC). Examine your automobile repair hands-on for the thermostat operation range, and also make certain you have the exactly one for her application. Or change it, if necessary.

The next video gives you an idea about replacing a thermostat in a car.

How to change a negative Thermostat

Car thermostat troubles can it is in diagnosed with these an easy troubleshooting procedures. They just take a couple of minutes and will assist you uncover the cause of an inexplicable engine operating temperature.

Even more, they'll assist you save your engine—and her wallet—from damage. If your troubleshooting procedures tell friend the thermostat is working, find the reason of the difficulty as quickly as possible. In this case, the auto repair hand-operated for your details car make and model will be of good help.

This article is accurate and also true to the ideal of the author’s knowledge. Contents is for informational or entertainment objectives only and also does not substitute for personal counsel or experienced advice in business, financial, legal, or technological matters.

Questions & Answers

Question: Where carry out I put the coolant in my car?

Answer: eliminate the radiator cap and pour the coolant v the opening. Monitor the accuse in your auto owner's hands-on or fix manual. You'll have to purge the system.

Question: just how long after instead of the thermostat does it take to obtain heat up?

Answer: The engine generally reaches operating temperature in around 15 come 20 minutes. That's as soon as the cooling fans kick in.

Question: I'm no getting any heat within my 2003 Jeep Liberty. What could cause an early 2000s Jeep come not warm properly?

Answer: Make certain there’s sufficient coolant in the system. Also, your heater core can be plugged and also not allowing coolant to circulate, or an actuator might be bad.

Question: mine 2003 Hyundai Sonata operation great, however the temperature gauge is constantly in the middle of cold and also hot. Is the overheating?

Answer: If the gauge is no in the red zone, it could be functioning fine. Otherwise, examine that the fan for the condenser is working fine when transforming the AC. Other potential problems could be a failing AC compressor, error in the cooling system, or a bad coolant temperature sensor.

Question: I just replaced my thermostat and now my car is end heating, and it wasn't doing that before. Do you understand what can be bring about my vehicle to overheat?

Answer: There could be waiting in the system. Examine your fix manual. If you don't have the manual, this post may help:


Question: ~ how many miles must a thermostat be replaced?

Answer: Usually, there's not a time structure to change the thermostat, yet keep an eye on the after five years.

Question: My truck won't start after the overheated what need to I check?

Answer: If that still cranks, inspect for spark and fuel delivery.

If the doesn't crank, eliminate the spark plugs and also see if that cranks. If the doesn't but the starter motor is engaging more than likely there's damages to the head gasket or engine.

Question: Why does my low coolant light remain on?

Answer: If the coolant level is OK, and the engine is not overheating, check the coolant level sensor.

Question: My automobile is overheating, yet the problem is the it sometimes overheats fast and also sometimes ~ 25 minute of driving. What might be the cause of my car's overheating?

Answer: There could be a trouble with the water pump. The bearing or impeller can be worn and not functioning constantly. If the pump is run by a journey belt, inspect the belt's tension as well.

Question: I have a 2005 Chrysler 300 Touring. When I to be cutting mine air on, it began to overheat, however today ns purchased this bars seal, and also it leaked from the head gasket. Now my automobile is running warm whether the wait is top top or not. What execute you suggest the trouble is? ns purchased the 32 disagreement bottle. What perform you think the trouble is?

Answer: If the head gasket is leaking coolant, it is no circulating correctly in the system. More than likely the bars seal won't cut it. You'll need to replace the head gasket.

Question: I have a 96 Mustang. The temperature gauge will obtain just under the red mark and also then drop down to the normal range. What could be wrong v my temperature gauge?

Answer: usual possibilities: the coolant temperature sensor or water pump is going bad, yet this can also be caused by a clogging radiator. A malfunctioning water pump can develop hot spots and also trigger the gauge to walk up.

Question: What wake up if I remove the thermostat from mine car?

Answer: there is no a thermostat, the engine will never reach the correct operating temperature. As well as an engine running below efficiency, engine materials wear will certainly accelerate. So, it's not a an excellent idea to operation an engine there is no a thermostat.

Question: have the right to I drive a short distance with a faulty thermostat?

Answer: just keep an eye top top the temperature gauge. Once you view the needle getting to the red line, pull to the side and wait for the engine come cool, if necessary. What you desire to protect against is engine overheating.

Question: The engine is no overheating and also everything else is functioning fine. However, the engine pan comes on as soon as ns switch the automobile on. Will certainly this cause problems as the winter to adjust in?

Answer: more than likely the engine coolant temperature switch, relay or wire in the circuit is faulty. Shot unplugging the switch and also start the engine. If the cooling pan doesn't come on, is more than likely the switch. If that keeps running, a relay may be stuck. You may want to inspect the diagram for your particular model and see if there's a relay in the circuit. And also check the wiring. Return rare, a manage unit may offer you trouble together well. This other post may help:


Question: Why am I gaining water in my spark plugs on my 2001 Ford Expedition?

Answer: interior leak: A leaking head or input gasket could be the problem. Various other possibilities incorporate a cracked head or block.

External leak: On some Ford explorer models the cowl deserve to actually leak rainwater right into one or more plugs. Water seeps v the well and can reason a misfire. Haven’t heard the this same concern on Expeditions. Yet check the boot and well because that signs.

Question: I have actually a Toyota Corolla 2005 I'm having actually heating and air problems. The heat blows cold wait in the winter, and also now that it's gaining hot the cold air wants to blow warm now. All of my vents and also everything works completely fine, and also it's filled with coolant. Might opening the thermostat cause this issue?

Answer: check the temperature gauge - unexplained readings may suggest a bad thermostat. You might want to inspect the refrigerant level and also condition, and also flow valve.

Question: What is the trouble when really hot waiting is blow on the warm or cool dial?

Answer: examine the refrigerant level. This issue additionally may be led to by a faulty condenser or part other problem in the system. This other article may help:


Question: go a thermostat in a vehicle have a switch?

Answer: The thermostat itself has actually a wax capsule that works as a sensor/switch, yet there’s more than likely a cooling pan thermostat temperature switch sensor.

Question: I have actually 2006 Honda Civic. Temperature gauge shows normal reading once fan off, however when I turn the heat on, the temperature gauge drops come minimum. AC functions fine. What might be the reason?

Answer: You probably need to replace the thermostat.

Question: have the right to just the real estate on a car thermostat it is in replaced?

Answer: Yes, you deserve to replace the thermostat housing. Walk to your local auto parts store or stimulate online. You’ll need the automobile make, model and also engine size to acquire the correct part for your application.

Question: exactly how do I know what thermostat have to I usage for a 2008 Chrysler PT Cruiser? It appears that there space some that can resist an ext temperature.

Answer: The thermostat need to be calibrated because that your details model. Just ask the males at the auto parts, lock should give you the right one for her application. If necessary, use your car's VIN number come avoid any confusion.

Question: I have a 2005 Chevy refer 1500. I adjusted the coolant sensor and also the thermostat yet my temperature gauge is still on cold. What have the right to be the trouble at this point?

Answer: check the wiring and connection in between the gauge and the sender or switch. You might need the wiring chart for your model and a check light or digital multimeter. Friend can find in your vehicle repair manual. If you don't have the manual, stop by your local auto components store. This other short article may help:


Question: I have actually a 2008 PT Cruiser. I confirm the radiator lid on it. It was poor so I replaced it. I thought that was the problem. My temperature began to rise, for this reason I reduced the auto off, let the cool for a while, then placed water earlier in the radiator. Then ns noticed coolant was leaking indigenous the optimal of the radiator yet the radiator appears fine. Might a faulty thermostat cause it to do that?

Answer: examine the radiator neck; an additional possibility is the radiator tank.

Question: I have actually a Toyota 80 collection Cruiser. I hooked mine float as much as go to an event. Drove 30kms and also it overheated. I drove home unhooked and drove 130kms come the occasion with no rise no problems. What could the worry be?

Answer: examine the pan hub, most likely the oil is leaking or there's something wrong through the assembly. This is typically the problem.

Question: I have a 2000 BMW E46 and also every 2 month the expansion tank cracks. Carry out I need to replace the thermostat?

Answer: This type of growth tank is under pressure. Make sure the tank's cap is working properly and also venting. Still, there might be one overheating difficulty or/and pressure issue. There might be several factors for this. Make sure you space not overfilling the system. Consult your car repair manual. A poor thermostat, cooling fan, water pump can cause the problem. Also, too much pressure is acquiring to the tank from; sometimes, a faulty (cracked) engine block, head gasket or cylinder head. This other post may help:


Question: I have actually a 2013 Toyota Yaris model and started overheating after ~ one hour drive on 120 speed. What can be the problem?

Answer: There could be several reasons for an engine to overheat. A faulty thermostat is only among them. This other short article can help you diagnose and, possibly, solve the problem.


Question: I have actually "Top-up Coolant" warning irradiate coming top top an turn off sporadically in mine car. The garage has actually charged me because that a turbo valve yet the trouble is persistent. I am convinced it is a thermostat issue yet no one will believe me together my vehicle is no showing any kind of other faults in a diagnostic test. Can you you re welcome help?

Answer: inspect the coolant level sensor. There could be something dorn in the circuit or the sensor itself. Friend probably deserve to do it if you have the repair manual for her model.

See more: What Area Code Is 559 In California, Fresno, Ca Local Phone Numbers

Question: How vital is replacing the thermostat casing?

Answer: If the thermostat housing is worn, damaged (cracked) or has start to leak, it's much better to change it. Coolant supplies the housing as a flow-connecting allude into the radiator. Some theremostat-housing come together a single assembly, for this reason you need to replace them together. If your is still good, and also seals good, girlfriend still have the right to re-install it.

Question: mine 2008 Ford explorer is tho overheating after an altering the totality radiator and water system. What is the cause?