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Chris
Chris, Shop Foreman
Category: Jeep
Satisfied Customers: 12741
Experience:  Jeep Certified Master Tech
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I have a 88 jeep with a 4.0 and I am forever fighting a

Customer Question

I have a 88 jeep with a 4.0 and I am forever fighting a overheating problem. I'm thinking about getting rid of the pressurized system. Do you agree?
Submitted: 8 months ago.
Category: Jeep
Expert:  Chris replied 8 months ago.

Hello and welcome to just answer. I am not sure about that because the engine cooling system was designed to be pressurized system. What have you tried so far to stop the overheating?

Chris

Customer: replied 8 months ago.
I have a two year old radiator (Aftermarket) The pressure bottle has a OEM screw on cap I replaced 2 times last year. the pressurized bottle has split the seam a few different times. I keep buying OEM bottles now but I tried a thick used Volkswagen one in the past. I think I had went back to OEM because I could not find the correct cap.
The water pump is stock. It's so difficult to get all the air out of the system. That's why I want to replace everything to make it a non German, non pressurized system. The Electric fan I installed a parallel HOT wire on a toggle switch so I'm not relying on the temp switch or the relay. I'll just turn it on after the thermostat opens and the gauge starts to drop.
I could Fill the A/C with R-12 but not with it over heating already, so yes it over heats with out the A/C and running the heater. I have replaced the blower motor at the heater core also.(there are no leaks inside either)
I have had this 88 jeep for 20years and this overheating problem keeps coming back.
Expert:  Chris replied 8 months ago.
Have you ever checked for any hydrocarbons in the cooling system which would indicate a head gasket allowing combustion gasses getting into the cooling system?
Chris
Customer: replied 8 months ago.
No, how do I do that? The exhaust is not blowing water after it warms up. The oil does not have water in it either.
Expert:  Chris replied 8 months ago.

There is a chemical block test kit that you can get from your auto parts store, It is part number BK.(###) ###-#### ***** uses a blue liquid that changes from blue to yellow/green is it detects HC in the resevoir bottle. See if you can rent a test kit from the auto parts store and do that test. If anything we can at least rule that out.

Chris

Customer: replied 8 months ago.
Chris I have a hard time getting to use a computer for the last few days to respond to you but I have been making phone calls about my problem. I contacted Auto Zone and O'Reilly's auto parts store and they don't carry anything to check for Hydrocarbons in the cooling system.
NAPA says they sell a "Coolant Test Kits" that checks for Dry Chemical Additives (DCA) type Supplemental Coolant Additives & (SCA) It is Part #4107 called a 3-Way Nitrite/Freeze Point/pH Test Kit. I don't think this is what you are talking about, is it?
Anyway, if I had a blown head gasket wouldn't it blow water vapor out the exhaust upon acceleration?
Or at high RPM the water would blow out the fill cap if it was off?There is one other thing I would like to mention. When trying to add 50/50, I have to have the engine at about 5,000 rpm to get the pump to pull the coolant in. If you accidently loose the high RPM then a lot of coolant comes back out the fill hole. Is that normal? It has always been that way. and some people I have talked to say it 's normal because of the pressurized cooling system..
Expert:  Chris replied 8 months ago.
No that is not the test kit I was talking about. When I get home from work later I will try and find it for you. Now as far as water vapors coming out of the tail pipe, yes, but if it is a small leak then it may not be noticeable. The fact that you have to rev the engine to add coolant seems strange to me. I have worked on those older Cherokees and never had to do that. Tell me when did the overheating first start?Chris
Customer: replied 8 months ago.
I have been fighting it for the whole twenty years I have had it. It has not been my daily driver for the last 15yrs. I use it to pull a wave runner to the lake. I leave in the cool morning before it gets too hot then come back down watching my temp gauge almost the whole way. Red lights are the worse with temperature climb. Low air and water flow.
Expert:  Chris replied 8 months ago.
Have you tried a new fan clutch? Does the electric radiator fan come on when the coolant temperature gets around 212?Chris
Customer: replied 8 months ago.
I have not tried a new fan clutch. I was thinking about a direct solid coupled one what do you think?
Did you research more about the coolant level in the bottle getting pulled in/down with high RPM's?As far as the temperature switch.This is what I wrote back on the 17th.
"The Electric fan I installed a parallel HOT wire on a toggle switch so I'm not relying on the temp switch or the relay. I'll just turn it on after the thermostat opens and the gauge starts to drop".
Expert:  Chris replied 8 months ago.

So then it is a fan problem. have you tried a new temp switch and/or relay? If not, then I think we need to try that next.

Chris

Customer: replied 8 months ago.
The temperature switch and relay work fine. I just added a parallel circuit (hot) to a toggle switch to turn it on directly, which essentially bypasses both of those components.
About the mechanical fan clutch. Should I get rid of the clutch so the fan spins faster?
Expert:  Chris replied 8 months ago.
Hmmm, that would be tough to do because the fan blades attach to the clutch assembly. Without it, there would be nothing to attach it to. You just might want to try a new one instead. When the fan clutch senses high temperatures, then it will spin the fan faster if it is working properly.Chris
Customer: replied 8 months ago.
Ok, I had no idea that the clutch was thermal controlled. I will get one on order today or pick one up at Auto Zone if they stock them.
Expert:  Chris replied 8 months ago.
Sounds good. Let me know if that fixes it.Chris
Customer: replied 8 months ago.
Hi Chris,
Yes it did it again after replacing the clutch fan. I drove it for 4 miles across town and at the signal lights it would climb to over 210 deg.
Once it sat with the motor off for 2 min then it started to bubble out the fill cap. The cap is less than one year old.
The bottle is also NOT hot at all. What do you think of that?
One more observation is that the top inlet hose to the radiator is hotter than the bottom outlet hose.
Expert:  Chris replied 8 months ago.
That sounds like a failed thermostat based on what you are telling me now,
Chris.
Customer: replied 8 months ago.
When I first start it up from a cold motor, the thermostat opens about 200. You can see the temperature drop on the gauge.
Customer: replied 8 months ago.
Also if it failed are you saying, closed? I did notice a temperature change between the coolant lines on the radiator. Which tells me there is some liquid flow.
Expert:  Chris replied 8 months ago.
It may be stuck closed or partially closed.Chris
Customer: replied 8 months ago.
Ok, I'll do that tonight tomorrow night.
Expert:  Chris replied 8 months ago.

Sounds good. let me know how it goes,

Chris

Expert:  Chris replied 8 months ago.

Hello, just checking in to see how it is going with the Jeep. If my answer has helped you, please help me by leaving a rating or accepting my answer so I may be credited. Rating or accepting my answer does not cost you extra. It allows me to be credited for my work. Please rate or accept in a positive way. You can ask follow-up questions after you rate or accept.

Thank you!

Chris

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