I've searched, and followed many of the suggestions I've found, but at this point, I don't know what else to do.

Basic Info:
1998 Jeep Cherokee Sport
146k miles

Symptoms:
Running warm, even at speed, around 212-215. In stop and go traffic, it runs up over 222. With the air on, it runs up over 222. If I leave the air on in stop and go traffic, or am in traffic for an extended amount of time with the air off, it will all of the sudden jump from 222 to 248 in less than a second. It will sit there around 250 for a minute or two, and then drop just as quickly back down to 222.

Attempted Fixes:
New Radiator
New Radiator cap
New mechanical fan clutch
New electric fan
New temperature sending unit
New thermostat
Flushed the Radiator when replacing the t-stat

Misc info:
Lower hose has the spring in it, so it doesn't appear to be collapsing
Upper hose is hot to the touch, so coolant is flowing at least part of the time
No leaks anywhere visible


Any additional suggestions would be greatly appreciated at this point. Only thing I can think of is the water pump.

thanks.

 

Hi, sounds like it needs to be "burped" for an air bubble. Raise the front end up off the ground and take off the cap then squeeze the upper hose while its running OR you can do it the easy way for $3.99 from AZone and get a "Prestone flush kit" and just take the cap off the "T" connector...Tj

 

I would have expected the shop that did the flush and t-stat replacement (because I live on a hill and didn't have time to do it myself) would have done that. Same symptoms exist before and after the flush, but I'll give it a shot. If I have the jeep pointed up hill, would that be enough, or does it really need to be raised?

 

That would be good and I dont think the shop would know it had to be done...Tj

 

It Is A "Jeep" Thing...lol...Tj

 

No dice on the burping, pulled off cap, started engine, no bubbles, just overflow out of the radiator as it heated up.

 

Anyone have any other ideas/suggestions?

 

One thing I don't see...waterpump. That very well may be the culprit. From what I have gathered even if it isn't leaking from the weep hole, it still may be on it's way out.

I'd also check to be sure the belt tension is correct. It may not be letting the mechanical fan run as efficiently as it should.

May also want to be sure the new t-stat is working correctly. Even out of the box items sometimes don't work.

 

I'm gonna second the water pump.

 

Hate to offer a simple idea...but make sure you use the correct cap. My system had a constant but minor leak. DPO had installed a 16 pound cap but the system calls for a 13 pound. Put a 13 on it...leak seems to have stopped. Sound silly, but maybe you have a weak cap and just need higher pressure.

 

Yeah, agreed with water pump. And DO NOT get a high flow pump if you are having overheating issues.. the high flow water pump doesnt let the coolant slow down in the rad to have heat blown off like a OE water pump. Go with NAPA, great stuff. What I did.

 

thanks for the replies. Interesting thought on the cap, it was just replaced, but I used a 16lbs cap. Might have to try that. I'll be a little bitter if it turns out the just be that.

Other than that, looks like water pump is the remaining option.