While performing the cooling system replacement, I removed the cooling system thermostat and housing in order to test it. I wanted to make sure that it was functioning properly as a part of the cooling system replacement.

The thermostat plays a very important role in the cooling system. It's a little valve in a three way junction that controls the flow of the coolant. When the coolant flowing through the thermostat housing is below a certain temperature, the valve stays closed and the coolant bypasses the radiator. As the engine temperature increases, the coolant temperature will increase along with it. Once it surpasses that certain temperature, the thermostat valve will open, allowing the coolant to flow through the radiator enabling it to cool more quickly.

An easy way to test the thermostat is to put in in some water that's heated on a stove. The valve in the thermostat should start closed, but once the water passes that temperature, you should be able to see it physically open.

I stuck a pot on a hot plate and dropped the thermostat and housing into the pot. You can take it out of the housing, which would make it easier, but I didn't. I also had a kitchen thermometer with me to track the temperature of the water to ensure that it opens within the spec. I wanted to put the spec here, but I don't have my manual as I'm writing this. Hopefully, I'll remember to come back and update it.

I tracked the temperature of the water and made sure that the valve opened at a temperature within the spec. The image below shows a comparison of the thermostat before and after the test.

You can see that the valve on the right (post-heat) is opened a little bit, meaning that it's working properly. There's also a spec for how much it should open, so I measured the width of the opening and confirmed that as well. Once this was done, I could confidently put it back in the car to to finish off the cooling system replacement!

Still interested? Go back to the Project Car page and check out how other things work!