SYMPTOMS OF A BAD THERMOSTAT
purpose
The purpose of the thermostat is to help the engine run at operating temperature. When the engine gets very hot, the thermostat opens up to let coolant flow through the radiator to cool it down and recirculate back to the engine. This prevents the engine from overheating.
On the flip side, when the engine is cold, the thermostat is closed to help the engine warm up faster.
Location
The thermostat can be found by following the lower radiator hose that goes straight to the engine. Although in some cars it could be found following the upper hose.
Normal operating temperature should be from 195° - 220° F.
When it comes to symptoms of a bad thermostat it can go in 2 different directions. There can be symptoms of a stuck open thermostat and there could be symptoms of a stuck closed thermostat.
symptoms
ENGINE LIGHT
The first symptom you might be experiencing with a stuck open thermostat is having an engine light on. A code known for this cause is P0128. This code means the coolant is taking longer than usual to reach operating temperature.
Ensure you can access your car's diagnostic codes by acquiring an OBD2 scanner here.
The thermostat can still be bad with the engine light off, so let’s move on to the next symptom.
warm up delay
The second symptom of a stuck open thermostat could be the temperature gauge taking longer than usual to reach the halfway mark. A stuck-open thermostat allows coolant to travel from the engine through the radiator which cools down the coolant and goes back into the engine.
Since the coolant process repeats over and over, it delays the time for the engine to reach the operation temperature.
lack of heat
The third symptom of a stuck open thermostat could be poor heating performance in the interior of the car. Since a stuck open thermostat will have coolant always flowing through the radiator to get cooled, it’s going to affect the heat in your car. A good thermostat will close at proper times allowing the coolant to heat up faster improving the quality of heat in the interior.
Temperature gauge on the hot position
The fourth symptom is your temperature gauge on the hot position. This means your engine is overheating. A stuck-closed thermostat can be the cause of this. Since the thermostat never opens, it will never be able to go through the radiator, which cools down the coolant that goes back to the engine.
leaking coolant
The fifth symptom of a closed thermostat is leaking coolant. The coolant could be leaking from the thermostat housing or it could leak from one of the hoses. This happens because as temperature rises, pressure rises, causing items to expand until they pop. In this case, results in a leak.
When the engine is warmed up, a quick tip to see if your thermostat is stuck closed is by feeling both hoses. If one hose is hot and the other one never gets warm, the thermostat could be the culprit.
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