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XJ STILL getting warm.

Blaine B.

NAXJA Forum User
Well, I replaced the thermostat.....thought that cured my problem, but it doesnt!
Highway or city driving - if I get the XJ's RPM's about 2500 for a short while, the temp will steadily climb th just below overheating. Even after I've accelerated and have leveled off to a lower rpm and speed, the temp will still climb. Then it reaches the high temperature and stays there until the vehicle is turned off. What could it be now? I was pretty sure it was the thermostat, but it's still doing it with another new thermostat.
Here's a pic of the temp when I was parked in the driveway. It won't cool down and will just stay there until you shut the vehicle off. Any more ideas?
Everything short of heater hoses in the cooling system have been replaced in the last year.
Temperature.jpg
 
I would guess fan clutch, but if everything has been changed in the cooling system, how about "burping" or bleeding the system to verify no hot air pockets are vexing you?????:dunno:
--Shorty
 
I have burped it and thought it was fine. Would air in the system only cause issues when above 2500 RPM and still continue causing you problems even when you were back down to idle RPM?
 
highly likely???? no.
possible-- sure.

you could have a small air pocket that "settles" into a less sensative location when cold and only "migrates" onder high flow conditions of higher RPM.

I personally would re-check belt, H2O pump and fan clutch, though. These seem to show problems at higher RPM and can cause extremely slow cooldown times after it heats up.

also check that the lower radiator hose isn't collapseing at high RPM and that the radiator doesn't have any cold spots after a drive (indicating a stoppage)

--Shorty
 
I might have overlooked it, but what year? Open cooling system or closed?

I would say a pressure leak somewhere. Is your electric fan kicking on? As mentioned, definitely feel the radiator (carefully) and make sure it is getting hot. Sometimes the air is so bad in the system that water isn't flowing.

How does the Jeep run otherwise?
 
and again, regardless of how fast you're moving down the road, give that fan clutch a spin when it's heated up and engine off, if it's still free wheeling, you need to replace it, or lock it down with a few bolts through it (search) that fan moves a lot of air and keeps the engine cooler, longer, than anything else in your cooling system, don't assume that you can just get up to speed and make up for the fan's effect it won't work
 
My bad, I forgot I don't have a signature on these forums. It's a 1995 Cherokee Country with the open cooling syste,

Fan clutch was replaced last october, FYI. Just checked today.....when I got home after the Jeep was running hot (according to the gauge), I spun the clutch fan with my hand and it didn't freewheel. It didn't even make a 1/2 rotation.....so I'm guessing it's doing it's job. If there's any further tests to check the clutch, let me know.

Jeep runs fine otherwise....below 210 degrees as well.
 
Yep, funny you should mention that. I'm going to replace it tomorrow.
I pulled it out (1/2" deep socket works just fantastic)

And when I pulled it out, I noticed this......LOL!

TempSensor.jpg


Maybe the added resistance of this break, and the extra engine vibrations at higher RPM would cause the gauge to show me an elevated temp on accident??
 
I don't know, I thought to burp it through this sensor hole you have to add coolant through the tiny hole....

I didn't.

To burp mine I just ran it with the rad cap off.
 
Blaine, I did burp mine (open system, 1992) through the tenp sensor hole with the XJ parked on incline (nose down) and did see air coming out (bubbles). I was told on NAXJA that air can indeed get trapped there and that's the proper way to burp it. So it may have been the burping after all. Anyway, great it isn't overheating anymore!
 
Funny, when I pulled the sensor I didn't see any bubbling. Just bright, green coolant.

I'll let you know how it is Saturday......2 hour drive and then a 12 hour offroad event, then 2 hours home.

I hope it stays cool, crossing everything on my body. lol.

Of course when I pulled the temp sensor I was in the driveway. Slight upward incline, nose up....so.....air would be trapped in the opposite end of the motor, if there was any.
 
It stayed cool. I got stuck in the sand and the temp rose to redzone for a tiny bit.

But now it's doing the same thing again. It'll stay below 210 for awhile then will gradually rise to around 225 and stay there until you turn it off. Electric fan is on the entire time. Like I said everything in the cooling system is brand new. It will even occasionally get to redzone for no reason.

Although the coolant level in the resivoir isn't any higher. Somebody suggested that a worn timing chain could be culprit, causing retarded timing which increases engine temp...although I replaced the cap+rotor about 2 months ago and do not recall any excess play in the distributor!

Sucks. I wish there was something more in the cooling system to replace, lol....but it's all new. Even replaced the cap, thermostat, and fan clutch again just to be sure.
 
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