How To Replace A Bad Thermostat In Your Car

The small and inexpensive vehicle thermostat is critical to engine performance. When it fails, your engine will not operate properly, which could lead to more expensive engine work down the road. Fortunately, car thermostat replacement is easy enough. Here’s a walkthrough on how to replace a thermostat.

What A Vehicle Thermostat Does?

The thermostat is essentially a temperature-controlled valve that allows coolant to flow through some or all of the coolant system. Its design is simple: It contains a wax element that melts when temperatures reach a certain level, opening the valve, and the wax solidifies again when it cools down.

On starting your engine, the coolant is cold and the thermostat is closed, so the coolant only circulates in the engine passages. As the engine warms up, the coolant gets hot, and the thermostat opens. This allows the coolant to circulate through the radiator and back to the engine. Here’s a full breakdown of the thermostat and other cooling system parts.

5 Symptoms of A Bad Car Thermostat

Your car, truck, utility vehicle, or van’s thermostat is responsible for releasing coolant into the engine once it starts to get too hot. This temperature gauge can go bad after about 10 years, so if you drive an older automobile, it’s a good idea to know the signs that the thermostat is having problems. Accurate Auto lists these signs below.

1. 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.

2. Air Temperature Changes

The thermostat can also affect the temperature of the air that flows into your vehicle through the vents. If the air temperature goes from hot to cold or cold to hot, this is a sign that your thermostat is not working properly. Oftentimes, these temperature changes are erratic and sudden. It’s important to have your vehicle inspected when you experience these interior temperature changes.

3. Coolant Leaks

Oftentimes when the thermostat fails, it remains in its closed position. As the engine overheats, coolant will overflow out of the thermostat housing. This means that coolant leaking out of your engine could be a sign that your thermostat has gone bad. It can also be a sign that you have a problem with your radiator hoses, the radiator itself, or the seals and gaskets.

4. 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.

5. Heater Problems

Finally, if your thermostat is stuck in the open position, no matter how high you turn up the heater in your automobile, you won’t get hot air blowing through the vents. You may not notice this problem right now since we’re quickly heading into summer, but if you did have problems with your heater last winter, bring your vehicle into our shop for an inspection.

How to Replacing a Car Thermostat: Step-by-Step Instructions

How to Replacing a Car Thermostat
  1. Locate your thermostat if you haven’t already done so. Most thermostats are located where the top radiator hose joins the engine, so these steps deal with this type. If your thermostat is in the bottom radiator hose, the principle is the same.
  2. Place a bucket under where you’re going to be working. Some fluid will escape, so have a clean two-gallon container handy to catch it, and return the fluid to the radiator when you finish the job.
  3. Remove the clamp. Follow your radiator hose to where your thermostat is located.
  4. Pull off the hose. This is when some fluid will escape and drain into your bucket.
  5. Remove the bolts that hold the thermostat housing in place and lift out the old thermostat. Compare the new thermostat and its gasket with the old ones. If the new thermostat and the gasket that’s included with it aren’t exactly like the old ones, go back to the store for the right ones.
  6. Lay the new gasket in place. There’s a gasket around the hole where the thermostat was located take that off, too. Scrape off any pieces of gasket that may be stuck, but be sure not to let these pieces fall into the hole!
  7. Drop in and secure the new thermostat. Make sure to place the spring-side down; then replace the bolts.
  8. Replace the hose and hose clamp. If your hose clamp uses screws, screw it down tightly but not tight enough to cut into the hose.
  9. Replace whatever fluid ran out of the hose by pouring it from the container into the radiator fill hole or coolant reservoir. Be sure not to pour it on the ground where children and animals can be endangered by it. If you accidentally spill fluid, wipe it up thoroughly before hosing down the area, and then place the rags in a sealed plastic bag before disposing of them.

Car Thermostat Replacement Cost

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. 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.