Wondering How to Tell If a Car Thermostat Is Bad ? Here’s a Complete List of Signs

September 9, 2020Car Care and Revamp
Blake Shaw

Bostonian and residential moving and packing expert. Blake Shaw enjoys bar-hopping, music, and writing insightful content.

As a driver, you know that the vehicles can malfunction at any given moment, some more unexpected than the others. However, figuring out how to tell if car thermostat is bad should be on the top of your priority list. With this knowledge, you will be able to prevent the engine from breaking down entirely and making a huge mess inside your machine.

Before you get down to work, you should know the answers to questions like How can a driver tell when their four-wheeler needs fixing? What are the signs of failing machinery? How do you test a car thermostat?  In order to help you with your DIY repair project, we created a guide that will successfully take you through the whole car fixing process.

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What Is Actually a Car Thermostat?

A car thermostat (CT), is an essential part of the vehicle’s cooling system. Its two main functions are to heat up the engine and keep it at the optimum temperature. CT usually uses a chamber containing a wax capsule that melts and gets bigger at a set temperature. Then this process operates a rod to unlock a valve that allows antifreeze into the radiator.

How Does a Car Thermostat Work

Vehicles with water-cooled engines need to maintain a specific temperature range in order to work. Depending on the make and model, all engines should operate at temperatures between 195 and 220F.

CT works as a control device that lets coolant fluid to go to the radiator at higher temperatures and not move at lower ones. Basically, it helps keep the temperature in the desired range, ensuring the best performance.

How Is It Related to Cooling in Your Vehicle

Did you know that an auto going down the freeway can produce enough energy to heat two average-sized homes? Since more than 70% of gasoline energy converts into heat, the job of CT is, and the whole cooling system is to stop the machine from overheating.

car engine
Get to know what the CT is before repairing it.

How to Tell If Car Thermostat Is Bad and Failing

Before you decide to pop the hood of your car and try to fix it, you have to know how to tell if your thermostat is bad and failing. However, if you know that there is something wrong with your four-wheeler, don’t hesitate to get down to business, especially if CT is the failing part. When your CT is bad, it will prevent the engine from operating in ideal conditions, which will later affect its overall performance.

How to Tell If the Thermostat Is Stuck Open or Closed

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. Additionally, a stuck open CT can cause problems with heat from the heating system.

On the other hand, if your CT is stuck closed, your machine will most likely overheat. If you don’t notice this and keep driving, your machine will self-destruct.

One way or another, your car will suffer damage. That’s why it is crucial to pay attention to all the warning signs your four-wheeler is showing.

Guide on How to Unstick a Thermostat in a Car

Sticking CT can cause serious problems to your vehicle because it is one of the most important cooling system components. If you are a gearhead who likes to tinker around machines, avoid a trip to a mechanic and fix the problem on your own in a few steps:

  • Step 1: Park on flat terrain and have emergency brakes on
  • Step 2: Wait until the machine is completely cooled
  • Step 3: Pop the hood and examine fluid levels, and ensure that they are not coming from the liquid tank.
  • Step 4: Locate CT, cause its location varies depending on a model of the auto.
  • Step 5: Unscrew the radiator cap and have somebody start the auto while you are carefully watching if the fluid is going to the motor.
  • Step 6: turn down the car and inspect CT pipes. The lower ones should be hotter than the top ones.
  • Step 7: Disconnect the pipes and see if there is any physical block in them. If they can’t move up and down, you located the main issue.
  • Step 8: Change valves in pipes. However, if the pipes are not the problem, you will have to figure out how to fix a thermostat in a car and replace it.
man fixing car
Follow the step by step guide, and you won't have problems.

What Are the Most Common Symptoms of a Bad Thermostat

You figured out how to recognize the signs that your CT is failing and that it needs to be replaced, but there are some symptoms that can tell your car needs fixing before it is too late. How to tell if a thermostat is bad without actually tinkering around the machine? While driving pay close attention to the way your auto is behaving, every different detail, no matter how small it can indicate that something is wrong.

The Bad Radiator Can Be One of the Signs of a Bad Thermostat

How to tell if your thermostat or water pump is bad or it’s the whole radiator? You will notice a few symptoms while behind the wheel that will surely tell you radiator, and with it CT, needs fixing.

Do you have shifting issues while driving? If so, know that fluid became polluted with coolant, and if not fixed, it can cause cracks and faults in the system. Additionally, if you notice that the passenger heater is not working, there might be a problem with heating. Since the heater relies on hot coolant, the radiator is probably clogged, or your water pump malfunctioned if the hot air doesn’t reach you. Take a look under your four-wheeler, if there are red, green, or yellow stains on the ground, the heating system is leaking, and when the fluid levels become too low, your machine will be in trouble.

How to Tell If Car Thermostat Is Bad When the Engine Works Badly

How do you know if your thermostat is bad in your car just by driving? Let’s be real, you know how your four-wheeler runs, so it will be easy to tell if it’s underperforming. Malfunctioning CT will decrease the performance of your machine. If not fixed immediately, this problem can cause reduced gas mileage and some more serious damages that will knock a lot of money out of your wallet.

How to Tell If the Thermostat Is Bad When the Temperature Fluctuates

When erratic changes in temperature in the motor happen, faulty CT is to blame. These strange heat fluctuations occur because the thermostat is not stuck in one position, meaning that cooling fluid won’t flow normally.

Overheating Is One of the Signs That Car Thermostat Is Not Working Properly

As a driver, you know that overheating can cause almost fatal consequences to your machine. It can occur if the cooling structure is failing, which includes CT, which can no longer run the way it should. When you notice the alarming heat, it is time to pop the hood open and fix the problem before the motor stops working completely.

man fixing car
Pay close attention to symptoms, and your car won't break down completely.

How to Test Car Thermostat on Your Own

Figuring out how to check a thermostat on your own is not hard, and it can tell you a lot about the shape your machine is in. Before you start testing, get nose pliers, and some gloves.

Put the gloves on and remove CT. Carefully inspect it and pay attention to its position. If it looks closed, everything will be okay. However, if it’s open, you should get a new one. Now, put a pot on a stove and pour enough water to cover the thermostat. When you submerge it, don’t let it touch the bottom of the pot. Use nose pliers for this. Start heating the water and observe the temperature. When your thermostat begins to open, write down the exact degree. Don’t pull it out of the water, wait until it is fully open, and write down when it happens.

When it is fully spread, pull it out of the pot, and then you can compare notes with the specification on your four-wheeler. If the results deviate from the specifications, you need to replace CT.

How to Check the Thermostat in the Car in Two Troubleshooting Steps

Are you wondering how to know if the thermostat is bad for sure? There are two troubleshooting steps that will undoubtedly show you if there is anything that needs fixing. The first one is checking coolant flow since your car is not moving, the liquid should not be flowing. If it’s flowing, it shows your CT is broken. However, if for some reason, you are unable to access a radiator cap, try the second troubleshooting procedure and check the coolant’s temperature, which should be between 195 and 220 F if it’s higher or lower it is time for CT replacement.

Use all the right tools, and troubleshooting shouldn't be hard.

Step by Step Guide on How to Replace a Thermostat in the Car

You figured out how to tell if your car thermostat is bad now it is time to get to work and put its replacement in. To help you through this process, we made step by step guide that will ensure your car is up and running in no time:

  • Before you start, the car should be parked on a ground level, and the machinery should be cold.
  • Get a screwdriver and remove the radiator hose clamps.
  • When pulling off the hoes, be prepared for some antifreeze to drip out.
  • Get a wrench and loosen the bolts that keep CT in place. Then just lift the cover, and the old CT will go out as well.
  • Clean out the dirt from the housing.
  • Get a new CT and put it spring side down in housing. Take bolts and reattach them. Do the same with hose and clams.
  • Check to see if you need to add more antifreeze.
  • Turn on the car and wait for it to reach the operating heat.
  • When it does take it for a test drive.

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How Much Does It Cost to Replace Engine’s Thermostat

Sometimes life gets in the way of your DIY projects. If you don’t have the time to figure out how to check the thermostat in your four-wheeler on your own, professional assistance is a solution. The price of replacement will depend on many factors, starting with the company you choose to handle your car. Additionally, the model and make of your auto will play a role in the final cost, as well as labor and antifreeze replacement. To get the exact price you will need to stop by the shop, let the professionals check your car before giving you the estimate. At the same time, while you are at the shop, schedule the next regular maintenance, and prevent your auto from breaking down again.

Regular maintenance is the best way to prevent damage.

Get a New Car and Enjoy the Trouble-Free Ride

When you are done with grease smudges and fixing up your four-wheeler, maybe it is time to start thinking about getting a new one. There are so many ways you can obtain a machine, like buying a car online, getting one of the top-rated SUVs, or even treating yourself with cool imported auto.

No matter which machine you get, you will need a reliable car shipping company to transport it to your home. Find an auto transport company that offers a variety of services, starting with open trailer car shipping and enclosed auto transport. Also, look into the door to door auto transport and terminal to terminal car shipping. While professionals handle your new toy, you can kick back, relax, and not think about fixing anything for a while.

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