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Running hot, after cooling system refresh.

S

subtle_driver

NAXJA Forum User
Location
Ramona
I have a 95 XJ with an automatic with a hot running condition. The needle almost touches the red zone on the gauge, but stays past the middle after warm up and never goes back. it just hovers there.... It creeps me out. I'm trying to figure out what the problem is, because this is for my GF, and I don't want her getting stuck somewhere at night. LOL!:piratefla

OK, I replaced the water pump, t-stat, 3-row copper radiator, backflush and new coolant 50/50, fan clutch, bled the cooling system, no leaks, runs great. Hovers at the high temp even though it is at idle and driving at all speeds. I replaced the t-stat with a heavy duty unit, but with the same results. NO change...

I read through the forums for hours, but I am not getting any closer.... I was thinking it was a temp sensor, what else commonly goes out on these beasts?
Any help would be great! Thank you!!!
 
You replaced the radiator, however does it have any cold spots? Also did you verify with your eyes that a radiator hose does not collapse?

How much is the sensor? When I worked in the industry (back in early 90's) I had an infrared reader that would tell me what temp. things were really. Perhaps that might tell you if it is real.
 
ya, I'm going to check the temp with a infrared reader tomorrow. and the radiator is consistant temp. And I didn't check the lower hose, I'll do that. thanks!
 
well the temp. gauge matches with the temp. gun. I removed the t-stat and it still runs warm.... the lower hose has a spring for reinforcement. what else is there to check?
 
What reading are you getting on the non-contact, and where? 210-215*F is normal (even though I don't like it...) and is nothing to worry about.

I'd add some Water Wetter if you're otherwise normal - since it's cheap insurance and might help to drop it down a couple degrees anyhow... I use it consistently, and I'm pleased with the results.

5-90
 
A touch elevated, but if it's consistent, it's probably normal. Try checking various spots on your radiator - you should note some gradient going across TO the driver's side, and a very slight gradient from top to bottom.

I'd also spot-check the hoses - make sure the upper hose is cooler than the lower.

Curious...

5-90
 
Bet you didn't get the cooling system burped. A gas bubble gets trapped at the rear of the head where the coolant sensor is. Unscrew the sensor slightly until antifreeze starts to come out, then screw it back in.
 
I would also replace the pressure cap with a 16lb one, they don't last forever and a bad cap will let it run hot.
 
XJTempSender.jpg
 
I've recently drained my cooling system to replace pump and thermos. Although everything seems to work OK I do get some more variability in the temperature which used to be much more constant. Didn't know about the burping. So the gauge sensor is loosened when the car is running right? Or after it has ran so that there's still some pressure on the cooling system, right?

From the picture I reckon this is not the temp gauge on the thermostat housing you're referring to (or am I not looking right?).

Thanks.

Tim
 
dutchjeep said:
I've recently drained my cooling system to replace pump and thermos. Although everything seems to work OK I do get some more variability in the temperature which used to be much more constant. Didn't know about the burping. So the gauge sensor is loosened when the car is running right? Or after it has ran so that there's still some pressure on the cooling system, right?

From the picture I reckon this is not the temp gauge on the thermostat housing you're referring to (or am I not looking right?).

Thanks.

Tim
Click to expand...
no, don't pull the guage sensor hot.
Elevate the rear of the jeep.
Pull the sensor cold
Fill with coolant until it comes out of the hole, put temp sender back in.
You are correct in it's location, it's all the way on the back of the motor, drivers side, practically under the MAP sensor on the firewall.
 
Just checked the cap. It says 13lbs. I take it that means 13 psi but I'm a bit puzzled. I'm not very familiar with the imperial system but for what I can make of it lbs is a pound right? So that's not a measure of pressure (as psi is). But anyway, let's say it's a 13 psi cap. If I mess up those infamous units here, let me know.

So I don't need to remove the gauge at the rear of the engine, is that what you're saying? Jacking on the front makes more sense to me than the rear, since we want the level to rise on the rear of the engine right?

So should I pull the gauge when the engine is cold and close up when the fluid comes out? Or should I let the engine run, jack the front, and just let the gauge be in place? If air gets trapped right at the gauge it makes sense to me to remove it.
 
Ok, will replace that one. What about taking the gauge out to let the air out? Yes or no?
 
i thought raising the front/rear of the jeep was dependent on whether or not u had a closed or open cooling system??
 
right on, i will bleed the rear sensor. I have a sensor on the front of the engine where the thermostat is and i thought i did it there. so I;m going to try that tomorrow. also, when the t-stat is in, i noticed that it only opens for a few seconds, then closes rapidly. the radiator gets hot then cold. but doesnt do it when the t-stat is out. it runs nice and cold then. but too cold. like around 150 deg.

so tomorrow i'm going to install a mopar t-stat. and bleed the rear sensor. wooot:cheers:

i also sent my GF home with some flush in the system. that may help a bit. peace....
 
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