Do you even know how
AO Gold Member
Join Date: Sep 2007
Location: South Africa
County: Western Cape
That thermostat in the picture is neither new, nor closed. It should be absolutely closed.
Why I say it's not new is because it is all rusty inside. I am going to give pointers on how to properly care for your thermostat in order to ensure that it works correctly:
1. Always inspect before fitting, and test it. It should be fully closed when at room temperature and once placed in boiling water it should be fully open. As the water cools to below 80 degrees it should start cooling again, being fully closed at around 50 degrees.
2. Always, always, always drain your coolant when replacing your stat. The rust and scale affects the operation leading to premature failure.
3. Replace coolant and add rust inhibitor to your coolant. Use at least 50/50 coolant mix. Even if you are in a temperate climate. It contains additives to protect your water pump, thermostat, rad hoses and prevent rust.
4. An open stat will eventually fail closed and cost you your engine.
5. An open stat will eventually fail closed and cost you your engine.
6. Revert to point 4 and point 5 above.
Please also note that the coolant should be replaced every 2 years, at which time it also makes sense to replace the thermostat. Even if longlife coolant is used, the thermostat will only last 2 to 3 years anyway.
A correctly functioning thermostat heats the engine up to 90 degrees within 7 minutes. The temperature should stay absolutely still at 90 degrees in town driving, only moving one needle width at most. If it ever moves more, for example to 95 degrees, then replace the stat. See points 4 and 5 above.
At freeway speeds the engine will cool to a minimum of 70 degrees (the line between 50 and 90). If the engine ever cools below 70 degrees then replace the stat. See points 4 and 5 above.
Last edited by Ian Lusso; 19-08-16 at 13:01.