How to Change a Thermostat

If you’re wondering how to change a thermostat then chances are the thermostat in your car has gone bad.  No vehicle manufacturers stipulate a regular interval for changing your thermostat so it’s only something you have to do if it’s bad.  Unless you’ve got a really new car with an electronically controlled thermostat, the only way to accurately test a thermostat is to remove it, put it in water and warm the water up and take note of the temperature at which the thermostat valve starts to open.

Since mechanical thermostats are one of the cheapest car parts you’ll ever buy, it’s usually a waste of time to test the old one.  Once you’ve gone through the work of pulling the old one out, It’s easy and cheap to just install a new one.  To help keep you from having to remove your thermostat “just in case” lets talk through the times you may want to replace your thermostat.

When to Change a Thermostat

  • If your engine has overheated
  • If your engine has gotten low on coolant
  • If your heat doesn’t blow hot enough air
  • If your car takes too long to warm up
  • Any time you’re draining your coolant

Any time your engine has overheated, it’s smart to change your thermostat.  If the coolant flowing through your thermostat gets too hot it can permanently deform the operating mechanism and can cause the thermostat to stick open or closed.  Similarly, if your vehicle isn’t making heat or takes a surprisingly long time to warm up it could indicate the thermostat is stuck open allowing too much coolant to run through your radiator.  Lastly, any time you drain the coolant from your cooling system say for a flush or to change another component, it’s worth sticking a new thermostat in due to the low cost and the benefit of knowing it’s working properly.

How to Change a ThermostatQuick Tips

  • Find it first!
    The thermostat in your vehicle is usually right near the end of one of the radiator hoses.  In most cars, it’s at the top of the engine at the end of the upper radiator hose.  In a Subaru, the thermostat is at the end of the lower radiator hose at the bottom of the engine.  In some cases, the thermostat may be hidden in an odd place and may be worth just taking it to a mechanic.
  • Make sure you get a gasket!
    Some thermostats come with a gasket.  Some don’t.  You should always install a new gasket with a new thermostat to prevent leaks so if the thermostat you purchased doesn’t have a gasket in the box, get one separately.  In some rare cases, the thermostat will use a form-in-place gasket.
  • Check your radiator hoses!
    while you’ve got your cooling system drained, it’s a good time to change anything else that is getting worn or needs to be changed.  If your radiator hoses are swollen or the rubber doesn’t feel firm you should consider changing them to prevent future breakdowns.
  • Use the right coolant!
    You can still get universal green coolant and it still works in almost every make and model car.  If you want to do things the right way, get the correct kind of coolant for your vehicle.  While this ensures the best protection it also will be the right color keeping your coolant color from getting muddy and brown just from mixing coolant colors.


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thermostat.jpg – By Mchebby – Licensed by Getty Images – Original Link