Signs Your Thermostat is Broken & How to Fix It

Odd Temperature Gauge Readings

Your temperature gauge should register cold when you first start your car and slowly build up to normal as the engine warms up. If the temperature gauge is reading lower or higher than normal, it’s possible that there’s a problem with the thermostat. If your car is overheating all the time, the thermostat likely is not releasing coolant into the engine to reduce the engine’s temperature.


Strange Sounds

Another sign that your thermostat is going bad is strange sounds. You may hear rumbling sounds coming from the engine, and these sounds could be coming from the radiator because the coolant is boiling. It may also sound like boiling or knocking. Sometimes the sound can also be gurgling. All of these things point to a problem in your cooling system.

Things to Consider

There are a few things that can help you if your car thermostat not working properly. 

  • It is important to check the thermostat regularly. Also, a little knowledge about a car can save the owner from big issues. 
  • Understand and check the temperature indicator of your vehicle. 
  • Check coolant frequently and don’t use water as a coolant.

The life of a car radiator thermostat is at least 10 years. However, proper maintenance can extend it more.

Troubleshooting Your Thermostat

You can test your thermostat to see if the unit is running the way it should. The following steps are simple and easy to do.

Test the Settings

Always make sure the thermostat is set to “heat” in winter and “cool” in summer. Also, make sure the unit is not just set to “on.” If it is, this can cause the unit to run continuously.

Turn the Heat Up, and Then Down

Turn the heat up 5 degrees higher than usual in the winter, and then 5 degrees lower than usual in the summer. When you do this, you should hear the system “click.” This should be followed by the sound of air blowing through the vents.

Replace the Batteries

This is always a good project for spring cleaning. Simple and easy to do, it will go a long way toward preventing a battery failure from leaving you cold at night.

Clean the Thermostat

Remove dust and debris from around and within the thermostat housing. This will protect the mechanical and electrical components from damage. Make sure to use a small brush and a dry cloth; never use water to clean the inside of the cover.

Test Connections

You will want to have a certified HVAC technician test the wiring connections during your regular furnace/air conditioner maintenance visit. It takes a few minutes and can catch wiring problems before they cause a failure.

Contact Preferred Home Services at (843) 405-3601 for more information about testing your thermostat in West Ashley, Summerville, or Mount Pleasant. Our certified HVAC technicians will answer your questions and schedule a service appointment to visit your home and ensure your HVAC systems are ready to go for the rest of the season.

How to Test a Car Thermostat

Before removing the thermostat from your vehicle, check the coolant flow and temperature.

Remove the radiator cap and idle the engine. If the coolant flows right away, your thermostat is stuck open. If it is not flowing, wait until your engine warms up. The coolant should warm to the right temperature and begin to flow after 10 to 20 minutes. If it does not start to flow, but the temperature gauge on your dashboard rises, your thermostat is stuck closed. If your coolant flows normally, there may be another cause of your overheating engine.

To check the temperature of your coolant, start with a cool radiator and engine. Idle your engine and use a thermometer to read the engine block or cylinder head temperature. Then, check the temperature of the upper radiator hose. Wait five minutes and test again. Complete the test a total of three times. If the temperature does not rise by much, your thermostat is stuck open. If the radiator hose remains about the same temperature, but the dashboard gauge rises dramatically, your thermostat is stuck closed. If the upper radiator hose rises to about the same temperature as the engine block, your thermostat is allowing the coolant to flow properly. You may have a different problem causing cooling issues.

To test the thermostat outside of the car, place it in a pot of water on your kitchen stove. Do not let the thermostat touch the bottom of the pot. Use a thermometer to see the temperature at which the thermostat opens. Note the temperature when it begins to open and when it finished opening completely. Remove it from the pot. Observe as it cools to see that is closes gradually. Compare your notes to your owner’s manual.

Car Thermostat Replacement Cost

Best places to order parts?  See: 19 Best Online Auto Parts Stores

The good news for those with a faulty thermostat i

The good news for those with a faulty thermostat is that it does not cost a lot of money to have it replaced. Of course, the exact cost will depend on the make and model of your vehicle. But for the average car owner, you can expect to pay between $140 and $300 for a professional mechanic to replace the thermostat in your vehicle for you.

The cost of the actual thermostat unit itself is usually between $20 and $80 but can be more for luxury or sports cars. The cost of the labor will be between $120 and $220 (possibly more if going to a dealership).

Remember that most mechanics will charge around $80 to $110 per hour for their services. The thermostat replacement job should take a mechanic about 1 to 2 hours to complete it. Therefore, you end up paying more money for the labor than you do for the actual thermostat part.

A lot of car owners try to save money by replacing the thermostat themselves. Unless you have some good experience working on cars or your vehicle’s thermostat is in an easy to reach location and you have a good repair manual to guide you, then you better let a professional do the replacement job for you.

After all, there may be another problem with your vehicle as well. You’ll want a professional so they can first diagnose the problem before replacing the thermostat.

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5 Troubleshooting Tips for a Bad Thermostat

Since thermostats are easily accessible, it should be the first place you check if you have trouble with your HVAC system. Here’s how to troubleshoot a bad thermostat:

  1. Check and adjust the settings: First, make sure you’re not jumping to conclusions about your thermostat. Check that the settings are correct and the temperatures you have programmed are appropriate for the season.
  2. Replace the batteries: If you have an electronic thermostat, remove the faceplate to expose the batteries underneath, and replace them. Make this a yearly habit to help prevent problems with your thermostat.
  3. Clean the thermostat: If you have an older mechanical thermostat with an analog lever to control the temperature, dust can cause a malfunction. Remove the cover and gently dust the inside with a soft brush or cloth to see if that fixes the problem.
  4. Check the wire connections: With the thermostat cover off, check that the wires are all firmly connected to their corresponding mounting screw. Loose wires could result in faulty functionality.
  5. Reset the circuit breaker: Your thermostat might have tripped a circuit. To find out, go to the breaker box and look for the furnace or AC circuit. If the breaker switch doesn’t line up with the others, flip it all the way off, and then back on again. This should restore power to the thermostat and fix the problem. If the circuit keeps tripping, you may need to have your electrical panel serviced.

Thermostat Location

The thermostat is often located in a plastic or me

The thermostat is often located in a plastic or metal housing near the water pump, connecting to the radiator’s lower hose.

It is most often located on the housing that connects the radiator’s lower hose, but it can be the upper hose in some cars.

Because it is often installed inside a housing, it is in most cases impossible to see with your own eyes without removing it, so to use a repair manual is a good way to find the exact location of your car model.

Have you found any signs of failure in your thermostat?

As an experienced manufacturer and distributor in the aftermarket sector, Dolz has a complete range of thermostats designed according to the specifications of the original manufacturers and using the latest technology.

All Dolz thermostats are OE equivalent:

  • Proven reliability. 100% tested. 
  • Premium quality. ISO 9001: 2015 Certificate.
  • Optimal design for maximum efficiency. 

Contact us for more information!