Overheating at highway speeds...??? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 10-02-2000, 02:10 PM
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Overheating at highway speeds...???

Please let me know if anyone has had this problem...

I've got an 89 YJ with 122K miles..6cyl/auto...I have just put in a new radiator, new H2O pump, 180 thermostat, all new hoses/belts...If I just let the jeep idle, the temp reads at around 190 degrees...If I cruise around town going 50mph or under, the temp still stays around 190-200..When I get the thing out on the highway the temp shoots up over 210!! The timing is set correctly and the fan seems to be working pretty well...I heard if your ratio of coolant to water is off, that may cause it...But why is it only at highway speeds...Please help...Thanks

Tommy B. in AZ -
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post #2 of (permalink) Old 10-02-2000, 03:05 PM
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Re: Overheating at highway speeds...???

At highway speeds your motor is working harder, and firing more often, which creates more heat. This makes your engine hotter. Check you coolant.

Kriss

post #3 of (permalink) Old 10-02-2000, 03:15 PM
 
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Re: Overheating at highway speeds...???

Check your return radiator hose and see if it has the spring in it, the hose can suck together at high RPM and cause over heating.

My Jeep is a work in progress, Happy Trails
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post #4 of (permalink) Old 10-02-2000, 03:18 PM
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Re: Overheating at highway speeds...???

the new lower hose didn't have a spring in it, so I put the old spring in the new hose...I made sure of that before I put it back together.

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post #5 of (permalink) Old 10-02-2000, 03:28 PM
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Re: Overheating at highway speeds...???

I'm not trying to be a smarta$$ or anything, but why is this just happening in the jeep when all the other cars/trucks I've ever owned stay the same operating temp whether they are going 20mph or 80mph...??

Tommy B. in AZ -
post #6 of (permalink) Old 10-02-2000, 03:38 PM
 
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Re: Overheating at highway speeds...???

Well you have a new hose and a spring in it so that is not your problem, sorry I could not help, but if I think of something I will let you know. When more of the guys come online you will get a fix, good lock.

My Jeep is a work in progress, Happy Trails
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post #7 of (permalink) Old 10-02-2000, 03:41 PM
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Re: Overheating at highway speeds...???

Thanks to all for taking the time to help me out with this.


Tommy B. in AZ -
post #8 of (permalink) Old 10-02-2000, 05:19 PM
 
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Re: Overheating at highway speeds...???

Tom what gearing have you got? I have 456 and when I get up to highway speeds I have to running around 3 grand (3 speed auto) and it gets a little warm at that rpm. before the tranny change out I ran around 2300 rpm in 5th with no heat problems.
GP'n

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post #9 of (permalink) Old 10-02-2000, 07:47 PM
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Re: Overheating at highway speeds...???

i think your gauge may not be exact.

my 87 reads a little high like yours but i know it's not overheating!

i watch my gauge all the time. it runs cool during cool weather and heats up when weather warms! i've traveled up-hill in slow 4wd with a tail wind and got as high as 210 according to gauge.

i have never replaced the water pump nor the thermostat but have installed a 3 row radiator.

although under high speeds it runs cooler with the added air flow through the radiator! you may have a point there![img]/wwwthreads_images/icons/smile.gif[/img]
post #10 of (permalink) Old 10-02-2000, 07:55 PM
 
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Re: Overheating at highway speeds...???

I think I can help. I had an '87 Cherokee with a similar cooling system. After doing everything you've done, I found that the hard coolant lines under the pressurized overflow bottle were clogged, and I was getting very little circulation. I ended up removing it completely and installing a radiator from a '92 with a regular cap. Then I installed a plain-jane overflow bottle. Problem fixed!

'86 CJ-7, 258, T-176, Dana 44 w/Truetrac, 4:11s, Weber, HEI, Borla header, Warn HS9500i

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