A broken thermostat can perfectly play the role of an unlikely villain, as it messes with the engine and cooling system. This control valve regulates the stream of coolant or water that flows into the engine, allowing it to warm up and operate at a safe temperature range. Depending on the temperature, this valve may open so that coolant will flow and may close when the coolant is no longer too hot. When this valve malfunctions, it may not respond to a certain temperature reading or signal or may get stuck in an open or closed position. This can be the cause of engine problems, resulting in blown head gaskets, car breakdowns, and warped heads. What could be a simple 10-dollar replacement can then lead to thousands of dollars' worth of repair. So before it's too late, know the symptoms of a faulty car thermostat.
Symptoms to watch out for
The engine overheats.
The engine will overheat if this control valve gets locked in a closed position, which keeps the coolant from flowing into the car engine just when it's running too hot.
The engine underheats.
If the valve stays in open position and doesn't respond to changes in operating temperature, coolant will be streamed into the engine even when it hasn't fully warmed up yet.
The engine temperature fluctuates.
A malfunctioning control valve may close and open randomly, which will result in irregular coolant flow to the engine. The engine temperature can swing wildly, making it run too hot or too cold. This will result in poor engine performance.
There are leaks in the housing.
A gasket fills in the gap between the thermostat and manifold. When this seal breaks, radiator fluid may escape and run onto the manifold, causing engine inefficiency and trouble. If there are leaks around the housing, you have to check the gasket that seals this control valve to the engine manifold.
The dashboard's temperature gauge isn't working properly.
The wild swings or any odd behavior of the temperature gauge on the dashboard can be a sign of a malfunctioning thermostat. If you notice these inconsistencies or irregularities, check the part to see if it's stuck or broken.
The MPG drops.
The control valve may be stuck or defective if you notice a decrease in gas mileage. A faulty part prevents a more efficient fuel burn, causing condensation in the cylinders that leads to poor fuel efficiency.
Replacing a defective thermostat
This control valve is typically enclosed in a metal housing. An inlet hose from the radiator is attached to the unit. It is sealed to the engine with bolts. In case this is your first time to check or fix it, you may use a manual to locate the part.
To remove the bolts that secure it in place, you'll need a ratchet. For easy access, you may use an extender to reach through the tight spots. The bolts may be a bit difficult to remove because of the heating and cooling cycle that makes them expand and contract. Once the bolts are out, you have to pull out the housing and remove the gasket. Before you put in a new gasket and sealer, make sure that all of the gasket material had been removed and that the area is clean.