Thermostat & Housing

What is an automotive thermostat and where is it located?

The thermostat in your car or truck helps regulate the engine’s temperature by controlling the flow of coolant to and from the engine. It sits inside a thermostat housing connected by hoses to the engine on one side and the radiator on the other. It can be found between the vehicle’s engine and radiator. 

The purpose of an automotive thermostat is to keep the engine around its optimal operating temperature. It performs this duty through relatively simple means, by blocking the flow of coolant from the automobile’s engine to the radiator until the engine has heated up and reached its optimal running temperature. When the engine is cold, coolant does not flow through the vehicle’s engine.  When you start your vehicle and the engine begins to get warm though, the coolant within it gets hot, and the wax pellet inside of the thermostat expands due to the heat. It usually does this around 195 degrees Fahrenheit but can vary. The expanding wax, in turn, pushes a rod that, due to the tension, springs open a valve that allows the hot coolant to flow through the engine and to the vehicle’s cooling system. The radiator then cools down the hot coolant and sends it back to the engine. This cools the automobile’s engine down, preventing it from overheating, which would derail whatever trip you had planned to take. As the coolant’s temperature starts to drop, the wax cools off and contracts, which allows the thermostat to partially or fully close, restricting the flow of the coolant. Due to these cycles of opening and closing, a relatively constant engine operating temperature is maintained.

How do I know if my thermostat needs to be replaced?

The most common problem with automotive thermostats is that the valve becomes stuck in either the open or closed position due to the wax binding up, debris becoming caught in the valve, or simple corrosion or wear. If the valve is stuck closed, then it won’t allow coolant to flow to the engine, causing the engine to overheat. The most obvious sign that the thermostat might be stuck in the closed position is if the engine overheats, as indicated by the dashboard temperature gauge reading in the red zone, or the appropriate warning light coming on. A knocking sound, like you might hear in a steam heat pipe, may be another indicator that overheating occurring from a broken automotive thermostat is occurring.

One way to check if your truck or car thermostat valve is stuck closed is to remove it, put it in a pot of water with a cooking thermometer, and raise the water temperature to about 195 degrees. If the valve doesn’t open, then it is not functioning properly. On the plus side, if this is the case, you’ve already removed the thermostat and are roughly halfway to replacing it. If the thermostat valve is stuck closed, it is important to get a thermostat replacement for your car or truck so that repeated overheating does not damage other parts of the engine. 

If the valve becomes stuck open, then coolant will perpetually flow to the engine, not allowing it to reach its optimal running temperature. If this happens in the winter, you may notice that your heater not blowing hot air. Other symptoms of a thermostat valve stuck open can be poor gas mileage or trouble shifting to higher gears in vehicles with automatic transmissions. 

In some cases, the thermostat valve may become stuck partially open. This causes some flow of coolant all the time, but never an optimal flow. This makes the engine take longer to warm-up, causing it to run sub-optimally, and then to eventually overheat. 

Can I replace an automotive thermostat myself?

Yes, if you have determined that you need a thermostat replacement for your car or truck, it is certainly possible to replace it yourself, although the difficulty of doing so will vary somewhat from vehicle to vehicle. The exact place of the thermostat will vary from one car to another, and it may be necessary to temporarily remove other parts to gain access to the thermostat. It would be advisable to find directions specific to your model before setting out on this particular repair. You’ll also want to allow the vehicle’s engine to cool down (especially if it has just overheated), and to have a bucket on hand to capture any leaking coolant, which can be dangerous to pets and children.

What is a thermostat housing and where is it located?

The thermostat housing (along with similar coolant ports) serves as an access point between the engine and other parts of the cooling system. It contains the thermostat, which helps regulate an engine’s temperature by controlling the flow of coolant to and from the engine. It is connected by hoses to the engine on one side and the radiator on the other and can be found between the engine and radiator. 

The thermostat housing acts as a cover for a vehicle’s thermostat and protects it from harm while also preventing coolant from leaking out. Thermostat housings were once primarily made of metal, but in more recent years manufacturers have opted to make these housings out of plastic instead to allow for easier manufacturing of complex designs while also lowering costs. However, the plastic housings can become brittle from heat and break due to over tightening fasteners or hoses upon installation.

How do I know if my thermostat housing needs to be replaced?

Thermostat housings can break down over time, which can lead to coolant leaks and damage to the thermostat itself. Coolant leaks can cause poor cooling and overheating, which can damage the thermostat. This can cause overheating to become a perpetual problem. Coolant also becomes acidic as it breaks down, so coolant leaks can damage other nearby parts. Pitting on the outside of the thermostat housing can be a sign that the thermostat cover is facing damage from the outside. If this occurs, it could allow in debris which can damage the thermostat.  Also, due to thermal expansion and contraction over time, the mating surfaces on the housing can warp or crack.

Can I replace a thermostat cover myself?

Yes, it is certainly possible to replace the thermostat housing cover yourself, although the difficulty of doing so will vary somewhat from vehicle to vehicle. The exact placement of the thermostat housing will vary from one car to another, and it may be necessary to temporarily remove other parts to gain access to the thermostat housing. Like the thermostat itself, it would be advisable to find directions specific to your model before setting out on this particular repair. Again, you’ll also want to allow the engine to cool down and to have a bucket on hand to drain the coolant, which can be dangerous to pets and children.