I've been getting an intermittent high temp reading and thought I would replace the thermostat in the truck since it was cheap and easy. I bought the thermostat and o-ring from autozone a few weeks back and have a question or two.

No gasket? Only the o-ring? Do I need to RTV thermostat housing to the block? Any gotchas? Any problems burping/refilling the system afterwards?

Do the factory thermostats stick open when they fail? I replaced the thermostat in my 89 Mustang a few days ago with an aftermarket piece that stated that if it failed, it would fail in the open position.

In my truck, about 2-3 times a summer for the past 2 years, the temp gauge will rise quickly and then the A/c will start blowing warm air. I would then turn the A/C off, crank the heater on high and then the temp would come down. Two minutes later, I turn the a/c back on with no overheating. I figured that the computer switched the a/c off if the engine got hot. This only happens about 2-3 times a summer. I watch the gauges when I drive, but my wife doesn't so much and she is driving the truck the next few days.

Coolant is fresh (flushed last fall).

Sorry for the long post.
Thanks,
Casey

 

If you clean the O ring channel properly there is no need for RTV, However I always apply a thin film (****).
Make sure the air bleed hole (T stat) is installed at the 12 o'clock positin and it will burp properly.
Dont over torque T stat housing bolts, (aluminum manifold).
When first starting after T stat change, open temp control to full, run engine until T stat opens, check for leaks, let cool, top up your fluids.

 

Thanks for the tips. I'll apply a thin film around the o-ring for good measure.

Casey