CherokeeInAZ

Hello folks, I am hoping one of you guys have a solution to my problem regarding overheating at idle after 15 minutes with AC on. I live in Arizona and it is hot.

The problem is the jeep overheats after an extended idle of 15 minutes with AC on. I have looked everywhere on the internet/forum and no one seems to have an answer to my problem. I am tired of throwing parts on it and it is not solving my problems because I can't see inside of the engine or the cooling system.

This is what I have done to it so far....

1) Replaced the following radiator, water pump, thermos, hoses, gaskets.

2) Checked for restriction in engine coolant passage ways.

3) Cold Engine compression test 155, 150, 145, 150, 145, 150 psi

4) Coolant flush

5) Belt

6) Heavy Duty NAPA clutch fan

7) Spend a lot of time cleaning the condenser for rocks and bugs. Repairing bent fins.

8) Radiator pressure cap

Okay as the following stuff tested the electric fan and it works well and all the electronics tested to be in good working condition and verified fan comes on at temp or when AC turned on. The Jeep will run all day between 210 to 220 F rock climbing, idle and bumper to bumper traffic and it does not overheat at all. Verified with infrared temp gun and OBD2 scan tool. When I turn on the AC the AC is cold blowing 35F in 110 F AZ temp. As long as the jeep is moving it does not over heat until you come to a stop or bumper to bumper traffic then it will over heat within 10 minutes of low air flow or bumper to bumper traffic only while the AC is on. I can turn off the AC and it cools off quickly back to normal temps within 4 to 7 minutes while in bumper to bumper traffic.

Jeep overheats when AC is on with low air flow....jeep runs normal when AC is off and stays at the designed temp of 210 to 220F.

The only logical conclusion I can come up with is that the condenser is building up a lot of heat during operations. I tested the heat of the condenser with infrared gun and it was nearly 200F. When the Ac is off the condenser returned to temps outside.

Either I need more airflow or condenser is restricting airflow.

Imagine an oven that is blowing 200 F on your radiator and the radiator in the Jeep is small so would that be the issue?

I have not tested for cracked engine block or cracked head/gasket. If either one was the issue I would be losing coolant, milky in oil pan, white smoke from tail pipe or bubbles in coolant.

Do I need to replace my stock Efan that has 530 cfm with a higher performance Efan of 1400 CFM?

I am lost here and trying to decide the best course of action.

99FreshenedCherokee

triple check the belt routing, then check it again, tha sounds like if you put the belt on wrong

CherokeeInAZ

Thank you, went and check belt routing and it is according to the fan shroud diagram sticker. Moved my flashlight around and caught something shiny and zoomed into with a led light. I found a wet small spot behind the radiator and it appears to be coolant leaking....

so with radiator with a small hole renders the radiator cap useless so the coolant goes into flash gas?

I need to replace my radiator again!!!! grrr

Thank you.

the_big_h

Sorry I don't really have an answer, just a couple observations:
My '96 XJ has similar problem, overheats with A/C on in traffic. New fan clutch, fad in good shape, new water pump. I have a few guesses as to the root cause:
1. PO added some perforated stainless steel mesh in front of my grille, to keep the bugs and stones out of the rad. I was thinking this was restricting my airflow - but since you don't have this mesh, maybe it's not really the cause of my situation.
2. When I'm pulling my camper, the engine has to work pretty hard sometimes (hills, headwind, or my heavy foot). The temp gauge starts to climb a bit, then I can hear the fan start to roar as the fan clutch engages. But when I'm sitting in traffic, I don't hear the fan roar, even if I rev up to same RPM's (2000). Why not?
- is the fan clutch getting so hot the fluid inside thins out, preventing it from engaging properly?
- is the fan drawing cold air from around the rad somewhere, preventing it's bimetal element from sensing the hot air? (fan shroud is in good condition)
3. Maybe when we're sitting in traffic, the hot underhood air is going forward, and being sucked through the rad again? I've never gotten out to check this theory.
I don't think a tiny leak will cause this problem. As long as you keep the overflow bottle level up, any coolant that leaks out will be replaced by coolant from the overflow bottle when the engine cools. But you should fix it anyways, else you will eventually run out of coolant, and these engines don't take kindly to being run dry.

CherokeeInAZ

You got me thinking....

I will take the mechanical clutch fan and put in a straight shaft. I don't usually rev the motor pass 3500rpms so the stock clutch fan should hold up. I can always install a flex fan with a straight shaft but nothing moves air like the stock mechanical fan.

All my stock fan shrouds are intact and functional.

http://www.summitracing.com/parts/FLX-14556/?rtype=10

I will have to measure it first to make sure what size is needed.