Hi All,

I am having some trouble with my 99 XJ. It seems to be having overheating issues when idling. I first ran into this when sitting in a parking lot and my original radiator blew. I had the radiator replaced and it has been ok for the last few weeks but now I was idling in a drive thru and the check gauges light came on and the temperature gauge was almost all the way up. As soon as I started driving again, the temperature went back down and the light went off. Any ideas on where I can check first. I tried looking for an existing thread as I am sure it exists somewhere but couldn't find it under the same circumstances.

Thank you in advanced!

 

Of course check to make sure your auxiliary fan is working properly.....
Also I recommend replacing the engine driven fan clutch..they go out.....they get weak....they are not expensive and its not a difficult repair.
The impeller on your water pump could be worn away, and causing low flow at idle, but some flow at 2-3000 rpm......
You said your radiator is new, so a stopped up radiator should not be the problem.....

 

Sounds like your fan clutch. Easy way to check is see how long it spins after you shut off the engine. Shouldn't go for more than a few seconds (if that long). If it spins pretty freely, then it definitely needs to be replaced.

 

So an update, I took another look at it this morning after the engine cooled and found there to be almost no coolant. So I would assume there is either A) A leak in one of the lines after having the radiator replaced, but I haven't noticed any coolant on the ground when parked or B) Maybe a leak in the head gasket? Idk if this would cause coolant to leak out or just mix with the oil.

Clutch looks good at far as I can tell.

Update: Oil does not look milky

 

A blown head gasket is obviously a possibility. Do you see any oil at all in the coolant (check and check again) or any green tint in your oil?
If you're leaking coolant into the oil it will very quickly destroy the bearings. How's your oil pressure?

You can have a leak that shows up under pressure but doesn't leave a puddle on the ground. Did you smell coolant in the engine compartment?

I would change your oil immediately and keep a small bit in a clean container. Then get an oil analysis on that oil - even if you can't see it, there can be coolant in it.

In the interim, I'd get a pressure tester from your local parts store (it should be a loaner tool) and put some pressure on the system and see if coolant sprays out of anywhere. It could be as simple as a loose hose clamp when the radiator was installed.

If you find an obvious culprit and don't see any more coolant loss, then you can do the analysis or just keep the kit for later. An oil analysis is never a bad idea, even if just to keep an eye on things.

 

I took a look at the oil and it doesn't seems to have any green tint to it and I can't see any oil in the coolant at the moment. I added additional coolant and a bottle of the "Bar's Leaks 2-in-1 Cooling System Repair" to see if that would help. Oil pressure idles just above 40. I am going to change the oil this week as its almost due anyway and see where it goes from there. Will keep this thread updated!

Thanks for the advice thus far

 

Did you replace the radiator cap?

 

No offence, but that was a really terrible idea. All you did was dump some "mud" into the cooling system which will plug all the small passages in the block, and tubes in the radiator. Get that crap out as fast as you can before it solidifies.
Some guys have to flush 10 times to get all of it out when their PO (previous owner of the vehicle) dumped stop-leak in.

Top off the cooling system and keep an eye on the oil cap for any milkiness, and any change in color on the dipstick. It will turn "chocolate" colored and start frothing if it is contaminated with coolant.

EDIT:
If you are overheating at idle, you have a flow issue. Either the water pump is not flowing enough coolant, thermostat not opening when it should, there is a blockage somewhere (not likely since you changed out the rad), or there is not adequate airflow through the radiator.
Hard to say which it is, but probably airflow if it only overheats at idle. Change the stock mechanical fan clutch, and ensure your electric fan is working properly (change it if so). Cheaper to fix the cooling system than pulling the motor if it overheats and warps the head

EDIT:
A failed radiator cap will also prevent the cooling system from pressurizing, I dont think my replacement radiator came with a new rad cap so best to make sure you eliminate that possibility.

 

^^^^ Sound advice.

Also, if Cruiser54 tells you to do something or recommends something, you should do it. He's one of the most respected and trusted members of this forum for a reason.

 

Hi All,

I am coming back to this after not having the issue for a while. Originally I had a bad radiator cap and the previous overheat was due to no coolant as it leaked out of the cap, replaced that and solved that issue. Now I ran into the issue again today, after sitting idle for 10 minutes or so. I have had the fan clutch checked and it looks good but I haven't seen my auxiliary fan turn on at all, and when I spin it, its hard to spin and makes a grinding noise. Is there 1 a way to test to make sure power is being supplied to the fan before I order a replacement, and 2 I assume the grinding feeling/noise is not normal?

 

Even if the auxillary fan does come on, its bad if cant be turned by hand, or makes a grinding noise. Replace it. If you still want to test it, disconnect it and jump both terminals directly to the battery. Dont worry about the polarity.

 

 

Replace the aux-fan for good measure, but my e-fan never kicks on unless I have the A/C on.
I can idle all day with the AC off and the temp never creeps up past 210*F

I think you should really just do a full cooling system flush, install a new water pump, thermostat and radiator cap (if not new). You should not have any overheating issues while just idling.
If that doesn't fix the issue, you likely have an airflow issue with the stock fan clutch