How to Diagnose Car Thermostat Symptoms

Series Summary

The thermostat in your car regulates the temperature of the engine. If it gets stuck closed, then the engine can overheat, potentially damaging the head gasket and other key engine components. If it gets stuck open, your engine will run cooler and your heater will not work. Either way, it's a good idea to fix a damaged thermostat right away in order to keep your car in good running order.

In this free auto repair video, you will learn how to replace a car's thermostat. Our experienced mechanic will tell you how to diagnose a thermostat problem, then demonstrate how to drain your coolant and remove parts of the coolant system, such as the serpentine belt and thermostat housing in order to gain access to the thermostat. Then you will learn how to remove the faulty thermostat and replace it, then watch detailed videos how how to put everything back together again. That the complete Expert Village treatment.

Video Transcript

"NATHAN MCCULLOUGH: Hi, my name is Nate McCullough on behalf of Expert Village. In these clips, we're going to talk about the proper way to remove and replace your vehicle's thermostat. In this clip, we're going to talk about the proper ways to diagnose your vehicle's thermostat failures. On this particular vehicle, there isn't anything wrong with the thermostat. I purchased this truck, it's a '91 Ford Explorer out west in Nevada. In the desert, they put a lighter duty thermostat in than they do in Michigan where I happen to live. The thermostat in the engine right now is rated for 160 degrees. In Michigan, about 190 to 195 degrees is recommended. This is due to this severity of winter. I've been driving it for a few months, this winter, and I have virtually no heat. Another way, if your thermostat has actually failed, they can fail two possible ways; it can fail closed or it can fail opened. If your thermostat happens to fail open, you will notice the same condition that I have right now. It will be stuck partially open and your heat will have lost most of its intensity. You'll notice that the gauge on your dashboard, your engine will be running cooler than what you're used to seeing temperature. The other way they fail is failed closed. If they happen to fail close, your engine will overheat and can possibly destroy the head gaskets or various other components. This, in particular, is a thermostat that will fail open. It is design that if it enhance a mechanical failure, it will stick in the open position. The reasoning behind it-the engineering involved in it is that it's better to have no heat than it is to have a thermostat freeze up in a close position and overheat your engine possibly causing severe internal damage. This is a thermostat that will fail either way. It has no advanced engineering or technology put into it. It's the cheapest one on the shelf. It is also, however, the only one available for my Ford Explorer. You maybe able to purchase one of these, a fail safe-as I like to refer to them as the fail safe thermostat-you may be not be able to. It depends on the manufacturer."