Yes, Another Overheating Thread

[Andy Steiner]

1998 Cherokee XJ 4.0, Auto, A/C, 6 inch lift, 31" tires, 3.55 gears, winch below line of radiator, 7" lights that are mounted in front of grill but have about 6" clearance.
Well I am about to get out the :explosion and make this thing go away for good. First off I am sorry to bring in another overheating thread... This one has got me stumped.

Everything I have done does not change anything at all. I have replaced the radiator with a 3 core, replaced thermostat with factory, had cooling system flushed, removed head and checked all passages, head was warped .005 so had it milled, verified fans are functioning, cleaned fins on condensor and verified that it flows with both water and flashlight, removed lights from front to help airflow, replaced coolant/water several times burping each time, removed cat converter thinking it was plugged all to no difference at all.

It runs at the line that is past 210 but cools below 210 when coasting down a long hill.

I am lost on this one any ideas will be welcomed...the next step is replacing the motor and at this point it is the only thing left that I can think of.

You've describe the EXACT same symptoms I had for two years after completely upgrading my cooling system.

In my case it turned out to be several small leaks that all attributed to the system not being able to hold sufficient pressure. First, bad radiator cap. And it was new. Replaced it symptoms persisted. Them found that the petcock wasn't fully tightened. It would leak when cool but not when warm. Tightened that. Was still loosing coolant and still not holding pressure. Mike Rollins and Charles Stein came over on the way to Moab last year to spend the night here in Vegas. We did a tune-up on my rig. When we removed the airbox they discovered this:

The plastic plug in the radiator where the temperature sensor for Renix engines mounts, was cracked and evidence of a persistent leak was visible. Couldn't find a new plastic cap, but the Renix sensor was only $8.00 so I bought one and cut the wires off. Since we installed that, my engines temps have been back to normal.

It took a couple of years to discover and repair all the small leaks in a new cooling system. They shouldn't have been there. I bought all new parts. It's a bitch that so many were defective.

Don't know what your problems are, but those were mine.