- In this page you will learn what a thermostat is, how it works and its location.
We will show you how to replace the thermostat in your car truck or SUV in this and the following pages with a step by step guide enhanced with pictures.

- What is a thermostat?
A thermostat is a device in your engine used to maintain a constant antifreeze/coolant temperature inside your engine.
Without a thermostat, the coolant in your car or truck would flow to the radiator all the time causing your vehicle to run below its operating temperature.
This would cause the following problems:
The car wouldn't be able to go in to closed loop due to the cold engine temperature, this translates in to higher emissions, poor fuel economy, and decreased engine efficiency.
Also in the winter your car would run so cold that your heater wouldn't work properly, causing the air expelled by the heater to be barely warm, if not cold.
So.......It is not good for a car to operate without a thermostat.

How do you diagnose a bad thermostat ?
There are two common problems associated with a bad thermostat, and they are:
1- THERMOSTAT IS STUCK OPEN:
This is the most desirable out of the two, because when you have a thermostat that is stuck in its open position, it will cause the coolant in your engine to circulate through the radiator all the time just like it would if your engine didn't have one, the way to know if your thermostat is stuck open is to start the engine when is cold, remove the radiator cap and look inside the radiator, if you see the coolant flowing, more likely the thermostat is stuck open, also, if you feel the temperature of the upper radiator hose, its temperature will be equal to your engine's temperature.

- THERMOSTAT STUCK CLOSED:
The least desirable of the two, this symptom will cause your engine to overheat extremely fast!!, causing a potential permanent damage to your engine like a blown head gasket, warped cylinder head(s) etc.
The way to diagnose a thermostat stuck in its closed position is to start the car and watch the temperature gauge in your dash, if it climbs to 3/4 and the thermostat is not open ; meaning that you can feel the temperature in the upper radiator hose and the radiator itself and it feels cold, while the engine's temperature is hot, stop the engine, you have a thermostat stuck in its closed position, ( assuming that your engine coolant level is normal), remember: A thermostat won't open if  the coolant level is low, because the way it is designed, the spring in the thermostat housing that makes it open and close, reacts to the antifreeze/coolant temperature, if the level is low, it won't reach the spring in the thermostat causing it to remain closed even if your engine is overheating, so make sure that your antifreeze/coolant level is in its normal level.

- Where is the thermostat located at?
Every make and model varies the location of the thermostat, but as a rule of thumb, it is usually located in the water outlet that leads to the upper radiator hose, very few makes and models have it reversed ( in the water outlet that leads to the lower radiator hose ), but there are some of them.
So, all you need to do, is follow your upper radiator hose, and locate the water outlet that is attached to the cylinder head, is very likely to have the thermostat in it.
Some vehicles equipped with a remote coolant reservoir, have the thermostat inside the radiator cap, and it is very easy to replace, just remove the radiator cap, and pull it out, the rest of the designs involve removing the water outlet.


Click on image to learn how to replace the thermostat
on 1986-1989 Honda Accord equipped with 2.0 L Engine 


In this page we will show you how to replace the thermostat in a Nissan pick-up with a 2.4 L four cylinder Z engine, and remember, these steps apply to most makes and models, however, as we get them in our shop, we will document the process to perform this job in different makes and models, that way you will have specific instructions that fit your make and model.