Hey Ya'll, Thanks for having me in your forum. I just bought my 88' 4x4 about 3 months ago and I don't know how I ever lived without it and thats the problem. It has been sitting more than gettin driven because for no good reason it will just up and overheat. I have replaced and completely removed the thermostat, replaced all hoses, the rad, the overflow, the pump and had the heater core check and it is good.
I am at a loss as to what could make this thing overheat all the time. A buddy of mine brought up that it might be a clog in the block itself and the more I think about it..... Thats all thats left.
That is unless one of you guys know something that I don't. Which is very possible, considering this is my first jeep. Does anyone know how I would go about getting a blockage out of the block? Also, when I do a tune up do I mess with the injection system? Any help would be greatly appreciated.

Tim

 

Replace your fan clutch, that's the only component you're missing. Real easy to do.

 

did you replace the cap on the pressure bottle as renix jeep use a pressureized cooling system ? 87 thru 90 are renix models

 

This....

And if your overheat only occurs at idle, replace your fan clutch.

 

Does it overheat at highway speeds? There's always a reason why a motor overheats.

 

I am starting to get the picture. Everything must be as the almighty Daimler intented or she won't work? Could the ECM lines being loose cause it to overheat too? I had to order those parts.



Yeah, I noticed the fan never comes on. I'll test it in the morning...
Although they are easy to work on, I have figured out that I am not a mechanic. I lack the mesh of patience, know how, and common sense it takes to do the job. As I was putting the thermostat in last night, I started lookin at the different heights of everything and the angle of the motor and realized that without a thermostat in this sucker the radiator has not been getting any water or very little. The amount of water in the overflow sure as LL isn't enough to keep that engine cool. I feel like a moron. But to my credit, I live in South Texas. We don't need no stinking thermostats (or so I thought). I would imagine, I fix that and the fan and I should be set. I'll keep ya'll posted.



---Quote (Originally by freegdr)---
did you replace the cap on the pressure bottle as renix jeep use a pressureized cooling system ? 87 thru 90 are renix models
---End Quote---

Ok. I have already admitted to being a moron, so I'll bite... Whats Renix mean? As for the cap I have several of them around here now. I thought those were the problem for awhile, but the last one came with the bottle I had to buy. I do see a difference between the OEM ones and the autozone crappy ones.


Thanks for all the great info guys. I'll get back with ya on my results..

 

driver side fan testing info, the fan cluch is on passenger side ...http://www.lunghd.com/Tech_Articles/..._Diagnosis.htm.... fan clutch linkhttp://www.aa1car.com/library/cooling_fan_clutch.htm

 

Make sure there is no air in the system.

 

You're not a moron. Renix is a marriage of Renault (the French carmaker) and Bendix and refers to the ignition systems installed on the AMC sourced 4.0L Jeep engines from 1987 to 1990. Chrysler switched to their own MPI ignition system in 1991. I'm fairly new to Jeeps too (three months in) and had never heard of Renix just a couple months ago. My dates and details might be off a little but you get the idea.

 

"Everything must be as the almighty Daimler intented or she won't work?"

Your Jeep was made just 1 year after Chrysler bought AMC. So it is very much an AMC design. Daimler has nothing to do with it.

Overheating can also be caused by a bad head. Ask me how I know sometime.

 

renix are a tough one to burp the cooling system.
i have vigorously squeezed the upper rad hose at temp while adding more 50/50 coolant. with enough patience, it worked for me.

also, the clutch fan is the mechanical fan, not the electric one. but the electric one should come on at a certain temp also. you can mod that one to be operated by a switch in the cab. use one with a light so you know it's on/off.

you need a thermostat, otherwise you will overheat.

 

I would absolutely check your rad cap and fan clutch. The fan clutch is really easy to check. Just give it a spin and it should NOT spin freely it should have same resistances to it. and it wont hurt to just change out the cap.

BTW, Where about is south Texas are you? I'm down in Riviera near Kingsville.

 

If u don't know how old the fan clutch is, replace it......the fan spin test is weak at best and fan clutch performance gradually deteriorates with time/miles. 5-6 mos. from now, that fan clutch needs to be at peak performance (as well as all other cooling system components). +/-$40 will get a new fan clutch and rad cap.

If there's no t-stat, the rad constantly has coolant flowing thru it, presuming the system is full of coolant.

 

It is not uncommon for machining chips to be left in the water jacket from the factory milling.

This is like thick rusty steel wool, and might be found in the lower area of the water jacket.

To remove it, you take out all the freeze plugs and hose it out with the help of a wire hanger.

I always try to use brass freeze plugs to replace the originals.

 

I would think 24 year old machine chips would long be desolved.