1989 4.o only overheats on highway....please help me :-( - JeepForum.com
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post #1 of 10 Old 06-11-2002, 11:25 PM Thread Starter
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1989 4.o only overheats on highway....please help me :-(

ok here is the deal i have a 1989 jeep cherokee limited with a 4.0 and one day i was driving it on the highway and it overheated to the point where it burst one of my radiator hoses. (yes it was an old hose) After fixing that i noticed my jeep would run in the red area after a bout 30 minutes on the highway but would cool down if i got off the highway and drove on ordinary town roads. i replaced the thermestat hoping this would fix the problem but it still runs hot and only runs hot on the highway.........please help with any sugestions!!

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post #2 of 10 Old 06-12-2002, 03:18 AM
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Is the water pump working, do you have a mechanical fan or a electric one. If mechanical is it a clutch fan check clutch fan if working properly may not spin clutches slip after awhile. If electric do they turn on. Do you have anything covering your radiator like fabric or cardboard? I would say thermostat but you have switched that. How hot does it get what size T-stat did you put in? How old is your coolant, do you have dexcool mixed with anything else coolants dont mix well. May need a coolant flush.Have you ever added radiator fix a leak, you know the stuff you add to plug a hole in the coolant it also plugs other stuff dont recomend useing it. These are some things to look into.

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post #3 of 10 Old 06-12-2002, 10:47 AM
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LOL, basically what HE said, LOL <img border="0" title="" alt="[Wink]" src="wink.gif" />
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post #4 of 10 Old 06-12-2002, 12:08 PM Thread Starter
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ok nothing is blocking the radiator and the fan is working fine so i guess i will try flushing out the radiator.......wish me luck..

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post #5 of 10 Old 06-16-2002, 08:31 AM
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i dont know what your actual problem is, but:

after screwing up the radiator and fan, i decided to get the rad re-cored to a 3-row. i also added an electric fan i had laying around.

anyway, driving down the highway...at 90 MPH, when it goes that fast...at 3-4000 rpm...with a/c on, the needle is just barely above the blue zone on the temp gauge.

just a cooling suggestion

and yes, i still have factory thermostat

Dan, San Bernardino, California

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post #6 of 10 Old 06-17-2002, 02:43 PM
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If you Have a Clutch type fan this is where problem will be .Your fan will work fine around town because it pulls enough air at low speeds but get on the highway and it does not let enough air pass through radiator .I suggest replacing fan clutch. I have seen this alot of times .
Good Luck ,

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post #7 of 10 Old 06-17-2002, 03:42 PM
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I had the same problem on an '87 XJ, and it was a BEAR to find the cause...
I found that the metal coolant lines under the pressurized overflow bottle were blocked, and not allowing coolant to flow properly. I probably could've cleaned out the lines, but I replaced the radiator with one from a '91 that had a regular cap. I yanked out the pressure bottle, rerouted the heater lines, and put a standard overflow bottle in. Problem solved!!
Again, you can try cleaning out the metal lines, and it may work for awhile...

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post #8 of 10 Old 07-16-2002, 07:09 PM
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Friend of mine just had the same problem with his Passat.

Spent a long time looking for a solution only to discover that partial blockage in his exhaust system.

It's worth a look!
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post #9 of 10 Old 07-20-2002, 09:12 AM
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I had the same exact thing happen with my '91 Wrangler. Replaced the fan clutch,radiator and thermastat......still happened. I pulled the water pump and found the impeller was corroded so bad it was almost totally gone. Replaced the pump and all has been good since (about 40,000 miles)

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post #10 of 10 Old 07-21-2002, 09:54 PM
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I had the same problem with a 90 Cherokee Sport. Before you spend any more money, purge the cooling system of all air.
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