Engine overheating

Welcome to Prius Chat!

How many miles on your Prius? Have you had the engine coolant changed recently? Any other work done in the recent past? How is the heat in the car (is it working fine)?

 

is your radiator getting warm?
if not, the thermostat is stuck/

 

I assume you checked your radiator fluid level? StarCaller's suggestion is good too - check that the radiator gets warm.

It's also possible it could be bad head gasket. If you have exhaust leaking into the radiator and causing air bubbles, this would cause overheating. Might try an easy check before you go through the bother of checking cylinder compression (don't need to pull plugs, just test whole engine at once):

 

If you have a head gasket problem most time the coolant expansions tank level be higher, discoloration of coolant dark dark red to brown instead of bright red, some times one can smell a odor in coolant, there also a test kit that detects hydrocarbons in coolant, pressuriding he coolant system to see if there a leak down some times it's a Crack cylinder head or block! the only way I know to test thermostats is to remove it and put it boiling water to see if it opens ! better to have a well season mechanic check it out!

 

Another thing it could be is the water pump. It would have the same symptoms (though I think the Prius would throw a code? Someone with more specific knowledge might know).

I've replaced a thermostat on a 85 Camry. They haven't changed much since then. Can be done at home, directions for most cars:

http://www.toyota.com/toyota-owners-online-theme/pdf/ThermoHowToBroch.pdf

Not sure where it's located, but if you look for a circular connector with two bolts on your engine with a radiator tube fitted, that's most likely it.

They're usually around $20, so if you're accessing it, you might as well buy a replacement. Be sure to get one that opens at the right temp - should be 85C if my scanguage coolant temp is correct.

 

+1 for TSTAT

 

Good to hear!

I would be inclined to replace it anyway though, before too long. At least watch it closely.

If it's got stuck once, it could be performing outside of spec, the opening and closing times, and have gaskets starting to harden and fray. When you do replace: place both thermostats in a pot of water on stove, watch their behavior as you raise temperature. If you've managed to get to it you're now comfortable with the process, and looking at maybe $30~50 for a replacement?

 

don't take a chance; rather get a new one //