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1999 JGC - Running Hot


 
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1999JGC
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Joined: 07 Aug 2007
Location: Virginia, USA

PostPosted: Wed Aug 08, 2007 4:42 am    Post subject: 1999 JGC - Running Hot Reply with quote

4.0 Liter Engine -
* Replaced radiator.
After driving 30 miles with AC on and I hit traffic or come to a stop then it begins to go above the middle mark on the temp gauge. It also does it if the AC is off. As soon as I start moving it goes back to right around or before the middle mark. It has a fan clutch and the fan blades do not easily turn when it has sat overnight or when it is running hot. I will be replacing the thermostat today.

Any suggestions?
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Duncan
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Joined: 09 Jul 2007

PostPosted: Wed Aug 08, 2007 7:31 am    Post subject: Reply with quote

Going over the middle mark on a hot day at a stop is perfectly normal I would say but going all the way up to the red area of the guage is probably not normal... You did not say how far above the middle mark it was going but here is a list of all the stuff I know can cause overheating:

Radiator:
You have already replaced this so probably not the problem.

Thermostat:
If its not working the fan will not come on when it should... Replacing it may solve the problem (double check to make sure it is actually working cause the weakest link in GCs seems to be the wiring... Chystler used HORRIBLE wiring harnesses in them).

Fan:
If the fan does not work your engine will still get some cooling cause the fan is mounted on one of the belt pullies so some air flow will still be provided as long as the engine is running. With the car cold turn on the AC (this should make the fan come on) and see if you observe a change in the speed at which the fan blades move.. It should increase)... If not disconnect the wires and use a multimeter to check for power... If there is power you can try sticking a couple wires on the fan and connecting them to the battery just to make certain it works (this can be done with the jeep off). If it IS getting power but not workign your fan is dead and needs replacing if it is NOT getting power and works then AND the thermostat has been replaced then there is probably a wiring problem or bad relay.

Water pump... I THINK this would cause the engine to get hot but the radiator to not boil over because the water would not be circulating.... I could be wrong though.

Head gasket:
There would most likely be water in the oil.

Obstructed airflow or baffle not in place:
If you have a winch some winch bumpers hold the winch high enough to obstruct airflow or check to ensure bugs and crap have not gotten in the radiator (unlikely cause it brand new) or air conditioning condenser which is probably in front of the radiator... Also ensure your baffle (shield thing around the fan) is properly placed... I lost the bolts to mine when I replaced my radiator so there was a little gap where there should not have been and when I finally replaced them I noticed my engine ran much cooler... Also I am told it will overheat rapidly if the baffle is not in place... Apparently it is more important than it looks...

Hope this helps...
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1999JGC
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Joined: 07 Aug 2007
Location: Virginia, USA

PostPosted: Wed Aug 08, 2007 8:00 am    Post subject: Reply with quote

Thanks for your reply!

Temperature Gauge: After I come to a stop with the engine on after driving it for 30 miles with the AC either on or off, It will go past 220 maybe 230. As soon as I begin to drive it again, the gauge will begin to come down and eventually it will sit around 200.

Thermostat: How do I check the wiring harness? I will replace the thermostat today.


AC Fan: The fan will come one when the AC is turned on. I checked it.
Question: Is it also supposed to run when the engine gets past 210 and the AC is not turned on?

Head gasket: I changed the oil recently and it was fine. No signs of water in the oil.
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Colinm
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Joined: 04 Aug 2007
Location: Seattle, WA.

PostPosted: Wed Aug 08, 2007 9:24 am    Post subject: Reply with quote

It probably won't be your thermostat. If it is restricting the flow, the movement of the air through the radiator won't affect the water that is stuck behind the thermostat on the engine side of it. Doesn't matter if it is air flow caused by the fan or by your jeep moving. That water just isn't moving to get cooled. I literally just replaced my fan clutch last week and it fixed the same issue you just descibed. mine might have been farther gone than yours, because when I had it warmed up and turned off, I could definitly tell that the clutch was weak when warm, but the best way to tell is to run it with the hood up, and operate the throttle at the throttle body to get a good idea of how fast the fan will spin when the engine is running.

Anyway, I highly recommend just changing the clutch. Shucks/Kragen/Krager auto parts had it for I think $82 dollars and it was a ten minute swap out. Don't even need to take the fan shroud off, at least on the 4.7L which I have.
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1999JGC
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Joined: 07 Aug 2007
Location: Virginia, USA

PostPosted: Sun Aug 12, 2007 5:01 pm    Post subject: Reply with quote

Update:

I have yet to change any more parts. I drove it today about 150 miles roundtrip with the AC on and temperature was in the 90's. If the jeep idled for a more than 5 minutes then the coolant temperature would rise. Sometimes if it idled more than 5 minutes the coolant temperature would not rise. The max it rose was 222 degrees. As soon as we drove again it would come back down to near 200.

Any comments or suggestions?
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Duncan
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Joined: 09 Jul 2007

PostPosted: Sun Aug 12, 2007 8:39 pm    Post subject: Reply with quote

222? Isn't that like... Not up into the red area of the gauge? I mean it is probably normal for it to run a LITTLE hot with the AC on in 90 degree weather...
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cajzmere
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Joined: 19 Jul 2005
Location: Rochester, NY AKA NY Tundra.

PostPosted: Mon Aug 13, 2007 4:45 am    Post subject: Reply with quote

"Burp" your cooling system, sounds like you may have air caught somewhere. Check your belt tension and condition. If it's slipping at idle, it will catch with throttle, and your fan will turn. What temp. thermostat did you install? It should open up at that temp. If it doesn't, it may not be working properly, or it's in backwards. I have had personally 2 t-stats bad new out of the box. and I have put 1 in backwards as well(that usually makes it overheat bad though). Good Luck.








Address all life's problems with "Occam's razor"
Address all Jeep problems with "Milwaukee sawzall"
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1999JGC
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Joined: 07 Aug 2007
Location: Virginia, USA

PostPosted: Mon Aug 13, 2007 12:35 pm    Post subject: Reply with quote

How do I bleed the system?
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cajzmere
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Joined: 19 Jul 2005
Location: Rochester, NY AKA NY Tundra.

PostPosted: Mon Aug 13, 2007 1:15 pm    Post subject: Reply with quote

http://www.radiators.com/radiator_how_to_maintain.html
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