97 Cherokee Sport Overheating - HELP
97 Sport 4.0
141K miles
New Radiator
New Rad Cap
New Hoses
New T-Stat

I just swapped out the radiator with new one from NAPA, changed T-stat, hoses, & cap and bled for air pockets. I did this as she was overheating when I turned the AC on. Temp was running 210 and then would do an IMMEDIATE jump to 250. She'd cool off and be good for about 5 minutes. Driving distance is only 6 miles to work and I MIGHT hit 50mph once.

Everything ran good for 1 day. On my way home, all of 5 minutes into my drive, I turn on the AC and she squeeled like a pig in heat and 1 minute later IMMEDIATELY jumped to 250. I pulled over let her cool off and finished my way home. She hit 250 again just as I pulled into the driveway andboiled over the relief tank...the fan come on as the should, there are no obstructions, and all the hoses are piping HOT, as should be

I've read a lot of the posts and cant seem to find one that matched mine...I need some help here...I'm mechanically inclined having grown up fixing cars, but have NEVER (knock on wood) had his issue.

 

there was a recent thread on this same subject and they exhausted all the areas to check or attend to. At worst, you'll need to consider popping the drain plug in the block to confirm you have coolant flow from front to rear or consider a new head gasket if you're seeing an oil/water mix anywhere.

I would drain the coolant to see if it all comes out - that may determine a blockage. Or run without a thermostat to see if the water pump is circulating coolant through the radiator.

 

Thanks! I didnt see that post...my eyes were pretty tired panning through. There is no water/oil mix, already checked that. I'll have to try without the T-stat this weekend. I'm new to Jeeps, if I need to pop that plug, where/what would I be looking for and what would base the relative ease on it?

 

Drain plug is near bottom at back of block - dunno which side but I think it'll be obvious compared to freeze plugs.

Just gotta be methodical about looking for the problem - try to do the least invasive things first.

Is the coolant moving through the radiator - top and bottom?
Run all tests with heater set to full high. Then shut off and watch gauge.
Do all the hoses get hot? Is flow stopping somewhere?
Does it still overheat with TStat out?

Eventually something won't be right and you'll be close to problem...

 

to my knowledge, flow is good. All hoses get hot. I've tried burping the system a few times and she'll run good only to have it kick back around. I swear its going to make me balder than I am. Hey, something that happened last night after I posted...I tried burping it again and when I was running it with the heater on high, gauge was at 220, but cold air...usually this indicated an airpocket, but not until it did it's instant overheat from 220 to 250 did I have coolant boiling out. I'm thinking this might mean the pump is toast...

 

Hey, sounds like a problem I am having but please do a quick test. See if the Jeep overheats with AC off and if it doesn't overheat then turn AC on and see how fast it overheats.

How hot is it outside?

 

She overheats without the AC on but it takes a good 20 plus minutes. I went out and grabbed a new fan clutch, water pump & Tstat. The last bit will be checking the plug as recommended if these dont do the trick. I'll keep ya posted this weekend.

 

There are easier ways of confirming coolant flow than pulling a drain plug.

 

^ honestly now, how useful was that post...

 

True that! I do have "suction" through the rad when I place my hand over the fill with the cap off. That being said, it seem Very minimal.

 

Dumb question:

Did you buy a 1 row or 2 row or 3 row radiator? I noticed some autoshop sells 1 row radiator and that is not to be used on the 4.0.

 

Not sure on this. I went to NAPA. I'll have to check it out tonight when I get home. Any way of telling if it doesnt say?

 

Sounds to me that your heater core is completely clogged. Take both heater hoses out and blow it out.

 

Ya I dunno.. I guess I'd expect, especially a Mod, that if they're gonna post at all, that they'd be a little more helpful than that.

But hey, just my opinion. Nothing requiring you to do so.

 

Get a mirror and a flashlight and go look at the radiator at an angle usually on top or bottom. Observe the passage you will see if it is 1 or 2 or 3 rows. It is not hard to miss what kind of radiator you have or you can get the part number on the box. Take the part number and look it up on NAPAONline.com and it will tell you what kind of radiator it is.