Cold here now in south Texas, okay cold to us, my son has a 1994 ZJ with a 5.2, heater does not seem to work, it may not have any tstat in it, what is the correct temperature rating for that year? 160 or 185.

 

Correct t-stat is 195 degree. No heat could be several possible issues. Plugged heater core or stuck blend door in the heater box are common causes as well.

 

Uninformed peeps like to remove the thermostat instead of properly diagnosing cooling system issues.

 

Believe it or don't, but the computer needs the engine temp to be at least 195* to operate in closed loop mode for proper fuel trim. Below that, it's relying on programmed data on it's chip. Normal operating temps are between 195* and 220*. People get nervous when it get above 210*.

Remember, a 50-50 mix of coolant at 16 psi boils at 260* and then steam pressure rises exponentially causing radiators and hoses to explode. Actually on a high speed run, no thermostat can cause it to overheat because the coolant is going thru the radiator to fast to give up it's heat! We found that in racing.

 

THX 4 the responses, no stat or incorrect one would explain what I consider a high idle condition, a core flush would confirm part B, what is the proper test for the blend door? This jeep is a limited with the high end climate control.

 

The automatic climate control has a built-in diagnostic check with trouble codes, but IDK how to enter it. I'll check my FSM and get back to you, but now I have to get ready for work. Sorry.

 

Dave did you use restrictor rings in place of the thermostat to regulate temps in your race cars? I used them since 1995 had a set of 6 of them made of thin brass looked like large washers the size of a thermostat. Started in the middle came to operating temps then changed them till I reached desired temp.

 

Of course, Fred! We started by just taking the valve out of a normal t-stat and in most cases that worked fine. If we needed one a little smaller, we could flatten out the flare part. Then there was always a Dremel! As a toolmaker, I had .030" brass shim stock available to make whatever we needed and my boss didn't care! He was one of the racers!