Thermostat Replacement


By Steven Bull

A common misconception with engines is the cooler, the better. That’s why your car warns you when it’s getting too warm, right? Wrong. Overheating IS a problem, but so is underheating.

Internal combustion engines are controlled explosions happening over and over. The bursts create heat and the engine is designed for that. In fact, they are designed to run at an optimal temperature — and that varies from engine to engine.

If you run it too cold, you’re not getting full performance because you’re not burning all the gas that comes through the engine. That also doesn’t do the environment any favours. Run it too hot and there is the risk of serious damage.

Luckily the wizards that design engines have a small, and straightforward, part that helps control this. And if you find your engine isn’t running at optimal temperature, the thermostat is a great place to start.

It’s not like what you have on the wall at your house, this is a small, round part with a spring that opens or closes depending on the temperature and that controls when the engine gets cooled.

The middle part is the vernatherm, to be hyper-precise, is a thermostatic bypass valve that is designed to open at a predetermined temperature to allow coolant to flow.

Scrabble triple-word-score words aside, all you need to know is if the number stamped on it matches your engine’s temperature. For this engine, it’s 160. When it reaches that temperature, the magic happens. The thermostat opens and, whoosh, comes the coolant to keep the engine from overheating.

If it’s not working, it will either let coolant flow when not needed or prevent it from flowing when it is needed.

This device is so special it has its own unique housing with a few hoses connected to it.

To get at it, remove the clamps and hoses and take off the housing. Be careful when you lift it not to drop the gaskets or debris back into the opening.

Sometimes the old gaskets are stuck on really well to the housing and need to be, carefully, removed with a knife.

While trying to remove the old thermostat, thinking it, too, is stuck and pulling hard with pliers is a common mistake. There’s a round, plastic housing that holds it in place that needs to be removed first.

Once it’s out and the old gasket gunk is removed, simply drop in the new thermostat and line up the notch on the plastic housing to slide it back in place.

Use sealing compound around the rim and place on the new gasket, then replace the entire metal thermostat housing on the engine.

Once you reconnect the hoses you’re good to go.

It’s one of the most under-appreciated parts of an engine, but one of the most important. Replacing it is so easy it can quickly be done in an hour if you have an easy to access engine!