It's not stuck open, the thermostat I took out did the same thing. When driving it will hit the 195º and the temp on the gauge will drop. I covered most of the rad and that helped so the mechanical fan is coming out this weekend.
Jeep Question
- Thread starter pontiacgp
- Start date
- Status
Bonnewagon said:"both heater hoses are as hot as the rad hose. " If the heater core was transferring heat into the passenger compartment, the return hose would be COOLER than the inlet hose. Not my logic, that's from the '01 Jeep manual. I'm thinking you should disconnect the hoses and blow both ways- see what comes out- if anything. I once saw a guy's hose blocked solid with crud, he thought anti freeze was a scam so he only used tap water!
My old Parcel Post diesel truck wouldn't even get warm without cardboard in front of the grill- it seems the maintenance garage felt no thermostat at all would prevent overheating in Summer.
My 00 S10 had no heat. It ended up being a plugged heater core. The Dexcool had turned it to brown mud in there. I flushed it, then the whole system and the Dexcool did it again. I flushed again and used Green cheapo antifreeze, been problem free for a couple years now.
My dad works at the VMF for the post office. It sounds like they only replace the broken parts, not what is causing the problem in the first place.
Steve, if the thermo-clutch fan is working properly, when cool it should free wheel. Maybe yours is stuck and is blowing all the time? I put a new one ($26 at RockAuto) on her's and you can hear it engage/disengage. By the way, did those hotter plugs help at all? 
the fan clutch does seem to be working but it still pulls the air just free spinning so maybe it's not as free as it should be. I heard that can be a problem. As for the hotter plugs I have them on order.. 
I havn't had time to play with it but I got out my laser temperature gun and the rad hose coming out of the thermostat is only at 145º after a 1/2 hour. I have the rad blocked completely with about 32 sq inches left exposed. The new Napa thermostat id coming out and I'll pick on up from the dealer. On a few videos they show a gasket like the one I got with the Napa thermostat and another round gasket that is used as well. I have also read that the only thermostats that work properly in a Jeep is one from the dealer. I don't know if that is bs or if I just had a bad one from Napa but the one before that acted the same as this Napa one does. The inlet heater hose is the same temp as the rad hose and the return line is a few degrees lower. I have never had a problem getting an engine to run hot except for this one. The cabin warms up after a while but my concern is the 4.0 engine needs to run around 210º to get their best gas mileage.
Steve, did you test those "bad" thermostats in a pot of water? I use a candy/frying thermometer and you wouldn't believe how many fail that test. A lot DON'T close when they should.
I'll test the one I remove and I think I still have the one I removed...with the amount of the rad I have blocked you'd think I can have no thermostat and it'd warm up... :?
Mark, I think I found the problem, on a video of a change of a thermostat on a 4.0 using a mopar part there is a gasket like the one I used plus a ring that goes on top of the gasket and it seals the thermostat. That ring wasn't in the box and it can't be found online. The thermostat I removed has no ring either. I'm thinking without that ring the coolant is bypassing the thermostat. I'll head to the dealer later and see if they have that ring without buying another thermostat
you'll see what I mean starting at the 50 sec mark...
[youtube]GbyFYLrGqVU[/youtube]
you'll see what I mean starting at the 50 sec mark...
[youtube]GbyFYLrGqVU[/youtube]
I'm familiar with the '00 and '01 4.0 motors and they do not use that ring, just a regular gasket. I also have been drilling a steam hole in every thermostat I use for years. It sure helps it burp all the air out. I hope that is your problem Steve, but I got my doubts.
- Status
Similar threads
