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XJ running very warm. Please help!!

Blaine B. said:
Well, using the contact thermometer today-

As the engine read above 210, the thermometer actually read around 180 or so as we probed various hoses, as well as the thermostat housing.

Now understand this is the temperature of the metal, not actually the coolant....so.....I'd assume it's a close reading, but perhps add another 10 degrees or so?

It was also suggested to me that my Dexron III smelled burnt. I did drain the pan twice, but it was suggested that I get the system completely flushed (one of those machines that drains the old and fills the new until it's completely full with new Dexron III).

Something about maybe the trans fluid is getting really hot due to its nastyness and is actually heating my coolant as it flows through the radiator and such. I do have an aux cooler as well. Since I do seem to have problems with the temp on the highway and such when there's increasd speed and such.

It appears my gauge is off though as well. By maybe 20-30 degrees?

Thanks!
Click to expand...

You definately need to use the OEM temp sensor from everything I have read the aftermarket sensors are not accurate with the jeep OEM gauge unless you recalibrate the jeep Gauge. That sounds like a big part of your problem right there. Overheating problems can be caused by transmisson problems. I would take your new Temp tester along with you and pull over when it is too hot (according to the gauge and check the tranny line temp going into the radiator heat exchanger and see how hot it is?

Eveything I have heard here is that the AW4 transmission does not like getting flushed!!!! Better to drain and refill, drive some, then drain and refill again several times according to 5-90 and other more knowledgable people around here. I have yet to touch my AW4.

On the accuracy of the hand help temperature probe, I find the rubber hoses being insulators read a good 10 to 20 degrees lower than the coolant flowing through them is, but the metal parts like the thermostat housing and radiator are with 1 to 2 degrees of the underlying coolant temperature.

Also, does the plastic reservoir look full to the top, like it is about to boil over too hot, or is it setting at the same level as when it is cooler like maybe 180 to 190 F?
 
I do have the open system. It's a 95 so no closed system!

The level of coolant in the resivoir is no higher than usual. Just about at the full mark when warm.....it didn't get any higher. I only thought it would get higher in a overheating boil condition (260+).

The temp sensor I have for the gauge is Jeep OEM.

I wasn't talking about a trans "flush" but rather a machine that just collects the old fluid as it pours new in. That's not really a flush is it? When I think of flush, I think of spraying something down and such......I'm not sure.

It's basically just like a blood transfusion if you think about it. Swapping out the old for new at the same time.

The metal inlet for my heater core was reading around 180 while the thermostat housing was reading around 170 or so. I left the temp sensor with my friend though, will have to get it and do as you said - pull over and check the temp when it rises.
 
outlander said:
quote: Blaine B,
"I have the closed system. I did try another cap".

:dunno:
Click to expand...
X2, I thought he had the closed renix system too so I was refering to the closed system bottle and closed system radiator mounted temperature switch.

In that case the computer is running the electric fan and it is basing its operation on the non OEM temperature sensor you bought. So if the electric fan is not coming on until the coolant hits a true 230 F I would blame it. If it is coming on at a true coolant thermostat housing temperature of 210 to 220 F I would say you are OK.

Is the OEM gauge Temp sensor new? Is the connector to it making good clean contact?

The 180 and 170 F measurements make it sound like the Temp gauge, wiring or temp sensor on the dash gauge set up is the problem.
 
Ecomike said:
X2, I thought he had the closed renix system too so I was refering to the closed system bottle and closed system radiator mounted temperature switch.

In that case the computer is running the electric fan and it is basing its operation on the non OEM temperature sensor you bought. So if the electric fan is not coming on until the coolant hits a true 230 F I would blame it. If it is coming on at a true coolant thermostat housing temperature of 210 to 220 F I would say you are OK.

Is the OEM gauge Temp sensor new? Is the connector to it making good clean contact?

The 180 and 170 F measurements make it sound like the Temp gauge, wiring or temp sensor on the dash gauge set up is the problem.
Click to expand...

I have the open system. That's what I meant but I put closed. Don't ask why :).

The coolant temp sensor I used was OEM, but used.....just a spare I had lying around. The gauge sender was brand new from the dealership though.

I've cleaned up the plugs that attach to both sensors. They weren't dirty but I claned them anyway.

I don't know, seems like the fan comes on at the right temperature, according to the gauge. Although maybe it varies and such if the gauge is inaccurate. Maybe I can pull a gauge out of another junkyard XJ and temporarily wire it up to the gauge sender so I can see what type of readings I am getting that way.
 
Blaine B. said:
I have the open system. That's what I meant but I put closed. Don't ask why :).

The coolant temp sensor I used was OEM, but used.....just a spare I had lying around. The gauge sender was brand new from the dealership though.

I've cleaned up the plugs that attach to both sensors. They weren't dirty but I claned them anyway.

I don't know, seems like the fan comes on at the right temperature, according to the gauge. Although maybe it varies and such if the gauge is inaccurate. Maybe I can pull a gauge out of another junkyard XJ and temporarily wire it up to the gauge sender so I can see what type of readings I am getting that way.
Click to expand...

Come to think of it the electric fan cut on temperature I gave you is what I have read here from others, all mine are renix, so I do not have first hand experience with your year.

What does the hand held temperature gauge read on the thermostat housing when the electric fan comes on.

Now that you have a hand held temperature gauge you can use it and your multimeter to test the temperature gauge sensor to see if the new one is bad. The hand held Temp meter will give you the gauge sensor temperature while the multimeter reads the resistance of the electrically disconnected gauge temperature sensor in ohms, then check the resistance table for the sensor to see if it is way off at 230 F.
 
Well, sitting in the driveway, the efan never came on. Thermostat housing was reading 180 degrees as I said, although the temp gauge was reading over 210 degrees.

I'll have to get that contact thermometer again and perhaps keep it in my rig, as suggested, so I could do "pullover checks" when the temp got up there and such :)
 
Blaine B. said:
Well, sitting in the driveway, the efan never came on. Thermostat housing was reading 180 degrees as I said, although the temp gauge was reading over 210 degrees.

I'll have to get that contact thermometer again and perhaps keep it in my rig, as suggested, so I could do "pullover checks" when the temp got up there and such :)
Click to expand...

Starting to sound like the cooling system is working fine. Sounds like the dash gauge, gauge sensor or the wire between them is off by 30 F.

Yah, I carry mine (IR Temp tester) around with me whenever I want operating on the road temperature data.
 
Ya, perhaps......although the efan is running alot when driving around town, so I know the temps must be at least higher than usual (A/C off)

Is it ok to use a new NON-DEALERSHIP coolant temp sensor? The one for the PCM and fan.....NOT the gauge?

I might just replace that as well with a brand new one for the heck of it instead of using a used one.
 
Blaine B. said:
Ya, perhaps......although the efan is running alot when driving around town, so I know the temps must be at least higher than usual (A/C off)

That sounds like an important point, not sure what we can conclude from it yet.

Is it ok to use a new NON-DEALERSHIP coolant temp sensor? The one for the PCM and fan.....NOT the gauge?

It it works properly yes. You should find a temp vs resistance table for that sensor in your years FSM and test it with that fancy new temperature tester and a multimeter to see if it is giving the proper resistance at several temperatures. I did all of mine already. Much better than guessing if they are good or not. It also helps me sleep better at night, LOL.

So either it is getting hot driving around (thus trigggering the Efan) with out the A/C on or the main computer temperature sensor is also reading high.

I might just replace that as well with a brand new one for the heck of it instead of using a used one.
Click to expand...
 
I didn't even realize that this thread was still going. Now that the temps are higher i have noticed it running just a little warm still. I've put off the new OEM sensors so far.

One difference i have though is when the gauge reads 225* in traffic my fan still won't kick on. I guess i finally need to buy that OEM gauge sensor.

I purchased an aftermarket cap and after some troubles i put the old one back on to compare and that took care of the coolant smell i was getting after driving. The NAPA cap was bad.

I will keep tabs on this to see what you come up with, and i'll keep it updated to let ya'll know what i come up with.
 
What year do you have?

If it's pre 96 there's 2 sensors. The one at the firewall-end of the block is for the gauge. The one on the thermostat housing controls the PCM fuel mixture, as well as the electronic fan.

So replacing the gauge sender with an OEM sender won't help the fan. Unless your thinking it's not actually 225 degrees, in which case the fan shouldn't be on.
 
It's a 94, I am under the impression that the aftermarket gauge sensor i bought is not relaying truthfull information.

I found a write up on hardwiring the fan to a switch so i can turn it on at will. That will be my next endevour. Either that or just start driving my truck until it cools down.
 
On the highway it should have. With all of that air rushing in.

I'll replace the coolant temp sensor with a new one. I'm pretty sure the gauge is to blame, and then perhaps the coolant temp sensor is turning the fan on too early - fooling me into believeing it's actually running hot!

I was on the highway yesterday and did a short burst of wide open throttle so I could merge on and such. The temp gauge rose and stuck in the redzone, so I pulled over and turned it off. Coolant level was normal and none came out. I started it back up after a few minutes and drove off. Temp stuck around 210 and such, but it did get up to maybe 220 and stuff just randomly. Will have to get that contact thermo again though.
 
Just noticed this tonight. It could have very well always been like this - but I'm just curious.

The little area on the center console below the ebrake lever is hot. Is that normal? I'm guessing it's heat from the trans ONLY and not the exhaust - although I'm not totally sure. There's no rust hole or anything under there, LOL. It could be heat from the transfer case too, right?

Just curious. How are yours on your own XJ's? Just noticed this today becuase somebody had their keys in there and wondered why they were so warm! :)
 
I once put a normal universal fan on my mustang and had huge overheating problems. It turned out that the mustang had a reverse rotation water pump and the fan was pushing the air back into the radiator. Check that the belt is routed properly to turn the water pump correctly.
 
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