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Running a bit hot, not overheating tho....

785 views 10 replies 7 participants last post by  GroundClearance 
#1 ·
Any suggestions? could it be the thermostat? its running around the line thats between 210 and the beginning of the red on the gauge. thanks
 
#2 ·
Mine was doing the same thing. It would only do it on the inerstate at higher speeds. I replaced the thermostat and it has not heated up any more.
 
#3 ·
I blew my plastic topped radiator 2 weeks ago, heat level was not even to 210 when it happened.

I replaced the radiator with an all metal heavy duty radiator, replaced the coolant and all that. Im still running hot.

One thing to look at is how fast your fan is running. Mine seems to be turning quite slow.

Other than a loose belt, what else could I look for?
 
#4 ·
I am also having the same problem at highway speeds with my stock 88 YJ. If I go over 60 miles per hour, I start running at 210 degrees, and if I shut off my Jeep and go to turn it back on in a few minutes, the temp arrow jumps up to around 220 or 230. After I get the Jeep started, the fan eventually kicks in and the temp goes back down.

This problem has been driving me nuts all summer so I have changed out the Thermostat and peformed a coolant flush, however, this has only helped some. The water pump has also been checked out, and it is in good shape. The guy at Autozone told me he owned a YJ also and not to worry about it, because during the Summer, YJ's with the 4.2 would run a little hot. This is a result of only having a one row radiator according to him. This doesn't sound right though, because many on here have mentioned they have upgraded the radiator and still continue having problems.

On mine, the only other fix I think could possibly solve this is repairing part of my fan shroud. During the March before last, I was driving down the highway and all of a sudden my radiator collapsed chewing up a bunch of hoses and my fan shroud. I may have to extend the shroud again, but if this doesn't help, I give up.
 
#5 ·
well according to the repair manual, it says it cant be the thermostat because the top radiator hose wouldnt get hot, which mine does. so now i'm wondering if its because i don't have my heater controls hooked up yet, perhaps it needs to run through the heater core and all of that to work right? i don't know what to do if thats not it. any help guys?
 
#6 ·
BlewMeAway said:
well according to the repair manual, it says it cant be the thermostat because the top radiator hose wouldnt get hot, which mine does. so now i'm wondering if its because i don't have my heater controls hooked up yet, perhaps it needs to run through the heater core and all of that to work right? i don't know what to do if thats not it. any help guys?
It doesn't help. I just installed a 4.0 into my rig, and hadn't put the heater hoses back yet....and it was getting warm...same as you, around 220-230. I routed new heater hoses a few weeks ago....still getting warm. I'm thinking new thermostat or radiator. When the 4.0 was in the cherokee I pulled it from, it never got hot. So I don't think it's engine related.....I'm thinkin a new radiator. But thats just my case. In your case, it could be either.
 
#7 ·
same here, i just finished installing a 4.0 from a cherokee that didn't have any heating problems either. So perhaps its the cheap radiator i bought? or maybe the radiator cap is bad? or perhaps the water pump?
 
#8 ·
also, it keeps fluctuating, it doesnt just stay hot, it keeps moving from 210 ish to 235ish, back and forth every few minutes
 
#9 ·
Make sure the thermal fan clutch is in good working order. The problem with belt operated fans is that they are always turning, however due to the viscous coupling of a thermal fan clutch the fan is supposed to rotate slower at highway speeds due to increased air flow.

If for any reason the fan is turning full blast at highway speeds this would cause the motor to work harder due to the increased drag of the fan blade, not only that but the rotating fan can actually impede airflow. If you have a Haynes manual it gives you the procedure to check your fan clutch.
 
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