I have noticed a strange temperature issue with my truck since putting a rebuilt 22RE in it about 9000mi ago. The old one had a BHG and the previous owner put Blue Devil in it and drove it for 60k that way. I figured a new engine was better than fixing whatever he'd done to the old one.

Issue 1: When warming up, the temp gage will continue to climb until it nearly hits the red, then after a minute will fairly quickly drop back down to about 1/4 on the gage(normal). This only happens when it's cool or cold out; over the summer it was fine. I used a new thermostat with the new engine. It seems like it's either sticking or not getting hot enough fast enough. Would poking a 1/4" hole in the rim of the t-stat help?

Issue 2: When I open the heater valve, the temp immediately rises somewhat and then slowly returns, then rises, returns, etc. My windows don't fog up with the heater on and my coolant is staying put, so I don't suspect the heater core. My old man had a '94 just like mine and his temp stayed rock solid all the time no matter what.

Opinions?

 

Does this sound similar to your problem?
http://www.4crawler.com/4x4/CheapTri...tml#Thermostat

Mine does it, too.

 

Just based on the behavior I'm seeing, I have been suspecting that this engine didn't employ a water bypass. I figured that the cool water under the 'stat wasn't moving, so the engine would heat up before it opened. That link confirms my suspicion.

 

mine does that to except it rises to the red in the summer then drops and it acts normal in the winter...ive changed everything and i just learned to ignore it

 

Living out here in the desert, I can't learn to ignore anything weird with a cooling system. I had a long line of cars with varying cooling problems, so I always have one eye on the road and the other on the gages.

My dad's '94 only overheated once when the top of the stock 230k radiator exploded.