It doesnt actually boil over; but it gets to max on the gauge and the electric fan cuts in. It will get really hot when driving slowly but is not too bad 70mph on the freeway I guess because of the cold air rushing thru the rad

 

it looks like the original one so its approximately 16 years old but the car has only done 70,000 miles and the rad appears to be in excellent condition; I flushed it out really clean using 2 cans of Wynns radiator flush.
Ive only bought the car recently and Im on a budget so Im trying to do one thing at a time rather than throw money at it!

 

indeed; but I drove it home over 130 miles on the freeway without it actually boiling over; the gauge simply read that it was hot (just in the red) and there doesnt appear to be any of the usual head gasket symdrones like cooking smells or oil in the water, water in the oil etc and no mayo in the oil cap

 

I really apreciate all the suggestions guys; the problems really make me scratch my head because there doesnt appear to be anything obvious or logical about the hot running.
Ive read so many posts about these hot running issues with Cherokees and it seems to be such a common problem; with many people replacing items one by one in a logical order but still finding that it will over heat anyway after everything has been replaced!
I will probably replace the fan clutch next; as although it passes the newspaper test (ie a single piece of rolled up newspaper will not stop the fan from rotating) it doesnt feel perhaps as stiff as maybe it should when trying to turn it by hand when the engine is hot.
Am I right in thinking that it should be quite stiff when the engine is hot; rather than it justs feels like there is a small about of drag to it?

 

U can't see the inside of the XJ rad (the outside is obvious).....having a rad shop separate the tanks from the core is the ONLY way to inspect it internally....from there, the shop "rods the tubes out". No amount of flushing with whatever chemicals will remove solids that have plugged off rad tubes from the bottom up.

The top half may be free flowing while the bottom half is plugged off. Half a XJ rad is not a good thing as the XJ rad is really dinky to start with.

I've never thought preventative maintenance was just "throwing money at it". Anybody that drives a 16 year old vehicle needs to learn how to "budget in" preventative maintenance or get ready to walk. A months worth of pizza and beer money buys a complete cooling system, including a new radiator, it's cheap and easy, but not free, like this advice. Git 'er done. U might be surprised at what forms inside a 16 year old radiator with 0 miles.

Presume the PO was the "king of neglect".

 

if your in the red driving 70 on the freeway it isnt a problem with your fans. i've seen a catalytic converter glow red before from being blocked up so i would imagine its a possibility but prolly not the problem. if you have fresh fluid thats topped off, a good radiator cap, and your confident that it isnt a problem with your water pump, then i would lean toward the exhaust being plugged. one way that you could tell is to buy one of those electric temp gauges and put it before and after the converter. you can buy them for cheap (got one for my brushless rc car motors) from harbor freight. if its alot hotter before the converter, i would replace it (if its rattling, i would replace it anyway just to rule out one more thing)

 

Thanks for the advice; and I totally agree! I will probably replace everything one by one starting with the simple cheap things (like I have with the T-stat) and next do the fan clutch and water pump and finally the rad too if need be. You'd be shocked how expensive Jeep parts are here in England tho lol!
Incidently; are air blocks a likely cause of problems on these engines or does that effect the more older models?
Cheers!

 

well i would clarify if i knew what i was doing. this is my very first car and have almost zero time to go to an advance auto or other places. As of now i have replaced the radiator. I had the block and head checked over with in the past few days and nothing seems to be wrong. my brother thinks its just a sensor in the gauge cluster. could that also be what's wrong? sorry for not clarifying anything. i have no experience on cars ha ha

 

That's how mine acted. Before I ended rebuilding the whole engine.

Then it still ran hotter than it should. Ended up pulling the remaned head, which had been magnafluxed by the machine shop, and replaced it with another one.

Problem finally solved.

I believe that head was cracked internally that no one could ever actually see.

 

Hope it works out ok for you; let us know what the result is!

 

Jeesh; that can happen! I'll continue along my investigative route and let you guys know what happens.
Hope its not a cracked head tho!!

 

Didnt read everything but for someone who may in the future and for the OP just incase... All the radiator shops here shut down... Radiators are to cheap on the internet now... I get mine off ebay for $100 shipped... Brand new and no hastle of pickup and drop off.. Plus I can scrap the old one and make a bunch of money back...

These flush kits and all that junk will never work unless its like a BG machine that does it while it running and uses two jugs of antifreeze... But even then those only work if regularly done according to manufactures timeline... And id say they work great on the engines side but id still replace the radiator...

 

Also for the cat my buddies TJ's clogged up... Melted all his o2 sensors (2004)... And he lost almost all power... Barely able to move it... But he never over heated...

 

To answer the original question - yes, a plugged or partially plugged cat/exhaust can cause overheating. Remember, most of the heat is carried away by the exhaust, not the radiator.

But he said at 70 it's not overheating, just at low speeds. Exhaust restrictions generally are just the opposite. Lots more heat is generated at 70 than idle.

If the temp sensor for the gauge is off, it would be off at both low and high speeds - the error would be constant.

Use an infra-red thermometer - measure the radiator at several spots. Cool spots indicate plugging.

Same thermometer, run at 2000 rpm for 2 minutes, measure the cat's inlet vs outlet - the outlet should be about 100 degrees hotter than the inlet if it's working. If it's the same temp it won't pass emissions tests. The rattle indicates it's coming apart inside.

Same thermometer - measure the water outlet at the t-stat housing - compare with the dash gauge to see if the dash is accurate.

Warm up engine to operating temp. Remove one end of the upper radiator hose from radiator, start engine - you should get a water flow like a fire hose - if not, suspect water pump impeller is rusted away.

 

Thanks for all the advice guys; I'm pretty sure now that it is the fan clutch after all so I'm going to order a new one in the morning. Will let you know the result!