How do replace the car thermostat?
If the engine warms up slowly, or never reaches normal temperature, or the engine overheats quickly, the thermostat may fail.
In most cars the thermostat is set near the casing under the pump on the cylinder head;The housing is directly connected to the top radiator hose.In some cars, the thermostat is located near the bottom hose.
Quickly test the thermostat by cold starting the engine.Place your hands on the radiator or top hose, away from the fan.
If the thermostat is working properly, the hose will stay cool for a few minutes and then heat up quickly.
If the hose gets hot from the start, the thermostat will get stuck.If the hose temperature is not high, but the engine heats up quickly, the thermostat gets stuck in the off position.
Make sure the new thermostat fits your car.The temperature at which it begins to open is usually printed on it.
Remove and replace the thermostat
With a normal top-mounted thermostat, you only need to drain part of the cooling system.Do not drain the engine when it is hot, otherwise it may burn you.Wait for the engine to cool.
Drain coolant from the radiator faucet or bottom hose until it is below the height of the thermostat housing.
If you want to reuse it, drain it into a clean container and filter it with muslin before pouring back.
Loosen the hose clamp and carefully loosen the hose to disconnect the top hose from the thermostat housing.
Remove the nut holding the housing.If the shell is not easy to lift, beat it freely with a piece of wood.Do not pry it open with a screwdriver, otherwise it may damage it and cause it to leak later.
Lift the thermostat.If the engine is cold but the thermostat is on, it becomes stuck and must be replaced.Otherwise, test in a water pot.
Before inserting a new thermostat, use a scraper to remove all traces of the old housing gasket;Please take extra care to avoid damaging the case.
Use a nail brush or a piece of wood to avoid scratching the metal.When doing so, close the opening with rags to prevent the old gasket from falling in.
Insert the new thermostat and gently apply the new housing gasket with a non-solidifying sealant.Put it in place and hold it in place.Tighten the housing nut alternately to avoid deforming the housing.Be careful not to tighten them too tightly.
Fill the cooling system with water and repeat the hose contact test, noting leaks.
Testing a thermostat in a pan
Hang the thermostat on the waterline of the pan and heat the pan.The thermostat shall not touch the side or bottom - heat generated by the metal will break the test.
Dip the cook thermometer in water and note the temperature at which the thermostat starts to turn on.It should be within three or four degrees of the number on the thermostat.
Continue heating to check that the thermostatic valve is fully open.
Neither the thermostat nor the thermometer should touch the bottom.
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