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Unread 07-10-2013, 02:09 PM   #1
Nik-Nak
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Overheating Issues 87 Cherokee

I have a 1987 Jeep Cherokee Loredo. I got the vehicle stock about 8 years ago. it has the 4.0L and an AW4 tranny. It also has the closed cooling system with the small plastic overflow tank with a presurized cap.

I replaced the radiotor about 7 years ago brand new and all the hoses and pressurized overflow tank.

I aquired another 1990 4.0L that I rebuilt from top to bottom. It was bored out 3000th's over and that is the only change in the rebuild, Everything else is still stock.

I just had my AW4 tranny rebuilt by Jaspers and it has like 200 miles on it.

As of today I have the rebuilt 4.0L from a 1990 and the rebuilt AW4 from the 1990 currently in my 1987 Cherokee with closed cooling system. It has all new hoses and Pressurized overflow tank (as of two weeks ago). The thermostat is working, the temperature sensor on the head is new and is also working. My gauge on the dash works also ( matches the temp in the radiotor hose using a thermal gauge).

I also removed the factory trans cooloer that was installed in the front and replaced it with a brand new one that is about 3 times the size of the factory one. While doing this I bi-passed the the cooler that goes through the radiator for the tranny lines.

It still has the radiator the I purchased and installed new 7 years ago.

Now to get to the issue......

Prior to the rebuild of the drive train from the 1990 It had the 87' 4.0L and AW4. It had 219,000 miles on it and although it was tired and burned oil it never over heated. Always heated up and ran at and around 210 degrees. The temp would creep up when ever i drove long hills at higher speeds such as I-5 sisque summit or Hwy I-40. Never anything bad.

Currently as of now It starts and runs great!!!!!! It has a ton of power and also works great at opperating temperature. It runs at about 210 degrees. I can drive it all day long on flat land and it stays at 210 degrees.

But if i drive it hard at higher speeds (60-70 MPH) and try to maintain that while pulling a hill the temparture sky rockets to 235-240 almost in the red! To maintain that speed while climbing the tranny is "kick down" thus working the engine and tranny hard.

As soon as I back off and quit working the drivetrain hard it will begin to cool back down and usually return to the 210 Degree temp. Not very condusive to driving on the freeway in southern oregon where we have lots of hills.

So I have "essentially" a stock drive train in a 1987 cherokee that over heats when maintaining freeway speeds when climbing hills!!!!

Any thoughts or suggestions would be greatly appreciated!

Thank you!

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Unread 07-10-2013, 02:27 PM   #2
RamboPants
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Did you burp all the air out of it? Does your electric fan work when its suppose to? If you did anything to the 2 fan wires make sure you reconnected them right otherwise it runs backwards! Could have been that Tranny cooler and that bypass also.
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Unread 07-10-2013, 02:35 PM   #3
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The system is burped and is working great. The electric fan works and and kicks on when it supposed to. Its not hooked up backwards because it has a male/female end clip. The tranny cooler is new and is 3 times the size of the factory one. And everything I have read about the bypass sounds like it is used more to help heat the tranny fluid to get it up to operating temperature?
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Unread 07-10-2013, 02:43 PM   #4
RamboPants
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Can you un-bypass that cooler fairly easy just to see if that's the problem? You might wanna start there.
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Unread 07-10-2013, 02:54 PM   #5
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Yes I can and I have. Same issue. I appreciate the thoughts and Ideas.
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Unread 07-10-2013, 06:50 PM   #6
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Have you flushed that radiator or checked your water pump?
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Unread 07-10-2013, 07:22 PM   #7
XJaySC
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Did you replace the cap?
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Unread 07-11-2013, 05:44 AM   #8
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Radiator flushed, Brand new water pump that was done when i rebuilt the motor, has brand new hoses and a new pressurized overflow tank with a brand new cap! (new cap and tank as of a couple weeks ago). More great ideas that you have both suggested that I have tried to no success.
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Unread 07-12-2013, 12:18 PM   #9
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Still seems like a radiator problem to me. just because you flushed the radiator doesn't mean it's working like new.
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Unread 07-12-2013, 07:28 PM   #10
RamboPants
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I would try a new radiator if you can afford it. My Jeep would randomly overheat for years until i replaced my radiator and haven't had a problem since.
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Unread 07-12-2013, 08:54 PM   #11
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Quote:
Originally Posted by RamboPants View Post
I would try a new radiator if you can afford it. My Jeep would randomly overheat for years until i replaced my radiator and haven't had a problem since.
Yup. And go to Napa and get a 703-1396 replacement cap for your bottle. These radiators don't flush well after 20 plus years.
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Unread 07-15-2013, 04:52 PM   #12
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Oh also if you have a leak or the top blows off your coolant bottle just put a hose clamp around your cap and tighten it enough that you can turn the top.
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Unread 07-29-2013, 09:54 PM   #13
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Thank you all for the helpful suggestions.

I went ahead and purchased a new aluminum radiator, overflow bottle and heater control valve for a 1993 cherokee.

I swapped everything out and got rid of the closed radiator system from the 1987 and now have the open system from the 1993!!!

It works great and no more overheating issues!

So in conclusion I am assuming it was my "not so old" old radiator!

Thanks again for the input and suggestions!
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Unread 07-29-2013, 11:32 PM   #14
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Glad it's resolved.
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Unread 07-30-2013, 04:56 AM   #15
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Glad it's resolved.
Thanks! So am I!
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