Overheat Issue
 

I have a 1992 Mazda 929. If I run the car without the thermostat, it does not overheat. As soon as I put it in, and drive it for about 5 minutes,it overheats. It also makes a whisteling noise like a tea kettle, ready to boil over.I checked the thermostat in boiling waterand it is ok. I recently used block-seal because I was told that I have a bad head gasket, after a pressure test of the system in a garage. I cannot figure out whatis going on. If you have suggestions/ideas, feel free to respond.

Thanx,
CO2Man [:-]

RE: Overheat Issue
 

I think you've got a bad thermostat.

Try a lower temp thermostat, I think you can get 165, 180 or 195 degree stats.

You want the thermostat to trip before the water gets to boiling.

RE: Overheat Issue
 

here's how to test your thermostat - remove it from the engine and put it in a boiling water. the spring should move, and if it works it should open widely, and it opens slightly or not at all i suggest you replaced your mazda thermostat with a new one.

RE: Overheat Issue
 

Assuming that your thermostat works properly (and is not a high temperature one) then is it installed correctly?

You can switch to a lower temperature thermostat to see if that resolves your problem, but you don't want to run without a thermostat at all.

Your engine is designed to operate at a given temperature. Below that temperature your car is not operating efficiently... If you don't have a thermostat (or as in my case it was broken open) then what happens is that your coolant flows continually from the start of the car and keeps the engine cooler than it should be. If you have a thermostat in it keeps the coolant in the engine until it reaches the operating temperature. Once that temperature is reached the thermostat opens, and allows the coolant to flow. That usually causes the thermostat to close again... After a few cycles like that the temperature of the coolant stabilises and the thermostat stays open. But the engine is hotter...

So, double check your thermostat is the right one. Replace it if it isn't working properly, or try a 160 if you've got a 180... But don't run without a thermostat. You might want to check your radiator cap too... It might be the wrong one, releasing at a lower pressure than is intended.

Z.