Roeboat

I have a 96 Cherokee Sport 4.0 and I am dealing with overheating issues. It overheats while driving or at idle, on cold days and on hot days.

Heater works fine. Fluid levels are good, and there is no leaking. There is def no oil in the coolant and exhaust is normal and def no white smoke. Reservoir is full with no leaks. There are no other fluid leaks of any kind. Head looks good. It starts great and runs great, without stalling or misfiring... it just over heats. It gets up to about 250's but I turn it off before it climbs any higher and I haven't let it get into the "red".

Things I have replaced...
-Radiator
-Water Pump
-Thermostat (and yes it was placed in the right direction)
-Fan shroud (grasping at straws!)
-Clutch Fan
-All temp sensors and fan related fuses
-Radiator Cap
-Serp Belt (and yes the pattern is correct)

Things I have done to it...
-Flushed the system multiple times including twice professionally flushed.
-Cleared air out of system
-Removed AC condenser to improve airflow to Radiator


My thoughts....
I am not impressed with the flow through the top Rad hose running from the thermostat housing. I have replaced the thermostat three times and confirmed it to be working in hot water with external temp gauge and it opens at about 200F (its 195F rated). Water pump has been confirmed to be the right one and it is moving in the right direction. Serp belt is DEF on right so its not that. Aux fan works when it is unplugged, but it wont come on when plugged in due to the sensor not receiving the hot fluid flow into the thermostat housing. But even if I start from a cold start, and have the Aux fan on the whole time (with it unplugged so it works) it still overheats.

Could there be some kind of other restriction preventing the coolant from either reaching the thermostat or preventing enough flow through it? Ive pawed around past the thermostat as much as I can, but could there be a restriction deeper in the engine block?
I have had all the freeze plugs replaced professionally. But now I wonder if an old freeze plug got pushed in and is causing restriction. Ive spoke with a few mechanics about that idea, but they all stated that it wouldn't restrict enough flow to cause a problem.

So, if it is indeed a fluid flow problem (which it might not be) and the thermostat is working then what could be causing that restriction?

jeepster427

Have u tried taking ur thermostat completely out or running ur heater on full blast cuz if it overheats with ur thermostat out and heater on its prolly the head gasket..

Moncheche

Belt routing. If you have your belt routing wrong you will be spinning the pump the wrong way. Double check that.

Air in the system is another cause of over heating. Have you burped it well?

Just a couple of the odd ball things we have seen go wrong with the XJ cooling.

As an aside, have you confirmed that you're actually getting that hot? Could it be that it's just a bad sensor? Better to err on the side of caution and shut down, but it's a thought.

Roeboat

-Belt routing is def correct
-Def burped of air

-It does overheat with the heater on full blast.
-I have not tried it without the thermostat

Could the head gasket somehow cause a coolant flow restriction? At about 240F the top rad hose is not even hot, and can still grab with bare hand without problem

Slick761

If the head gasket was installed wrong it would cause this. Other then that the only time I've seen this was caused by a large air bubble.

Mrjw1996

could you explain how to "burp" the radiator...im very curious..thanks!

thakmfb

sound like a large air pocket

OttawaXJ

Thermostat. Its not flowing to the rad.

Rudy

Just in case:

Slick761

He said he tried a couple t-stats, thing is if he has air in the block it can cause the t-stat to stay closed. Happened to me but I drilled little holes in my t-stat so when my temp hit 215 and I felt the hoses and they were cold all I had to do was give it a few good revs and it pushed out the air and opened the t-stat.

x91evo

are you sure its over heating? maybe its a bad temp sensor

bigvig

He did say he replaced all the sensors, but that was my first thought too. You could always have a bad sensor or bad connection. If youve replaced everything and done everything youve said honestly, there is either an air pocket in the coolant (which WILL burn a head gasket faster than anything) or you have a bad connection somewhere. If you didnt burp your coolant, youre going to have an air pocket and it WILL burn through the head gasket.

You burp it by turning the heat to high, forcing the coolant to cycle through the entire system pushing the air bubbles out all the while adding coolant to fill it to its max. It will push the air bubbles out and allow the system to suck in more coolant. I do it using a "Spill-Free" funnel. Its a MUST for doing your cooling system.

djb383

I believe a properly functioningt t-stat will open in air or liquid....tested one on the center rack of the oven, it opened in air just like it did when in a pan of water.

Johnny9Inches

This may sound like over kill but knock out your freeze plugs and make sure that around the cylinders is clear, I think a new kit from summit is like $9, I actually have one that I would be willing to ship to you $9 plus shipping.
It was recommended when I swapped my head to do this, but I inspected around the cylinders and they were clear so i didn't punch mine out.
If its full of stop leak, or rust it wont cool properly of if its full enough not at all, no amount of water can keep it cool if water isn't getting to it.

nitsche.6959

I had this problem once on my 95 Cherokee and found out the radiators are a little under sized and the aluminum radiator are **** to electrolysis do to electrical feed back and that if the water you put in has high mineral content u can clog up the tubes. I replaced my radiator with all copper one and proper water and every thing was fine