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Another Overheating Issue

N

Nine Mile

NAXJA Forum User
Location
NJ
Hey all, searched and searched and read and read for hours on this one.

Vehicle is a 1995 4.0L/Aw4 XJ that is all stock.

We were having a problem with overheating at high speeds (70+ MPH) and when worked hard (like up long hills doing 40-50, etc).

Did a rad flush with Zerex 15 minute flush, put in a stock Mopar Theromstat, put in new stock Mopar hoses (so the lower is not getting sucked closed), rinsed block out with distilled water, and it is still doing the same thing.

What do you guys think? Time for a new rad and water pump or just one of them or what?

It gets almost to the last white line before the red zone....that's usually where we turn the heat on and back off the gas and it goes back down to 210.

Thanks in advance.
 
There's hundreds of posts on this and other forums about XJ overheating. Did you see this one...

http://jeepsunlimited.com/forums/showthread.php?t=656646

when you were searching?

I had the same problem on a '93 4.0 stock. Water pump had already been replaced, and hoses were OK. Flushed the rad out, which seemed to help.

Although the standard diagnosis suggests that if your fan clutch is failing the temp will rise in traffic, not on the highway, I nevertheless suspected the fan clutch (little resistance when turned by hand....) so I replaced it. Since then I have had (touch wood) no overheating problems.

br1anstorm
 
Sounds a lot like me. If I were you I would go for the new radiator and depending on how old your water pump is I would replace that as well. I have a new radiator on order now that I will install this weekend. It makes sense to replace the basic items first like hoses, rad cap, thermostat, etc, but looking back at all the things I used to fix my overheating problems (like trying 80/20 water/coolant, water wetter, 180 thermostat, the list goes on) if I would have just done the radiator right away I can hardly imagine those things were necessary.

I ordered an all metal 2 row from radiator barn. There is an endless debate on this forum, along with anywhere you search on the internet, about aluminum, copper, plastic tanks, all metal, you name it. The 2 row all metal I ordered, according to people on this forum who have used it say it fits perfectly, works great, and is only 130 shipped. I don't need overkill, I just wanted something solid.

Lastly, about the water pump; my original OEM pump lasted 110,000 miles. Before I started doing my own work, I took it to a mechanic to put in a new one, unknown brand... I now have 140,000 and am on my 4th water pump, and as you may guess I am back to an OEM one; no problems. I have a hard time believing your problem is only your water pump. RichP puts it simply, overheating on highway is a sign of bad radiator. If you think about it, the heater acts just like another small radiator, if your temp goes down with the heat on this likely means the radiator can't handle the load by itself.

One more thing, about the radiator flushes. I, along with others on this forum as far as I can tell, have had bad luck with the 10-15 minute idle flushes. On the other hand, I have used the 6 hour cleaners and those really get the crap out. It may be worth running one of those before putting in new equipment to be sure you get as much crap out of the engine block as you can.
 
Just a thought...Check to make sure the fins on the radiator aren't clogged with dirt/debris. Maybe try flushing with water or compressed air...just don't use to much pressure, be careful not to damage fins. Also... confirm that your electric fan if operating properly...hopefully this helps...
 
Hi,
I have a 93 XJ 4.0 AW4 and that, like yours, had an overheating problem. If I ran the a/c it would start to overheat so I had to turn it off and put the heater on, this is just what you want on a hot day! I fitted a new waterpump as it was leaking and also a new radiator, I also locked up the clutch fan just to be certain it was doing it`s job. I can run all day now with the a/c on, no problems. Looking back I don`t think I needed to lock up the clutch fan, the noise is not much more than normal so I`ll leave it as is for the time being. I feel safer with it running a bit cool rather than overheating!
 
br1anstorm said:
There's hundreds of posts on this and other forums about XJ overheating. Did you see this one...

http://jeepsunlimited.com/forums/showthread.php?t=656646

when you were searching?

I had the same problem on a '93 4.0 stock. Water pump had already been replaced, and hoses were OK. Flushed the rad out, which seemed to help.

Although the standard diagnosis suggests that if your fan clutch is failing the temp will rise in traffic, not on the highway, I nevertheless suspected the fan clutch (little resistance when turned by hand....) so I replaced it. Since then I have had (touch wood) no overheating problems.

br1anstorm
Click to expand...

Yep I've read that one numerous times....I was just trying to confirm that what I was thinking was correct before spending over $200 in new parts.

Thanks.
 
pauldo39 said:
Sounds a lot like me. If I were you I would go for the new radiator and depending on how old your water pump is I would replace that as well. I have a new radiator on order now that I will install this weekend. It makes sense to replace the basic items first like hoses, rad cap, thermostat, etc, but looking back at all the things I used to fix my overheating problems (like trying 80/20 water/coolant, water wetter, 180 thermostat, the list goes on) if I would have just done the radiator right away I can hardly imagine those things were necessary.

I ordered an all metal 2 row from radiator barn. There is an endless debate on this forum, along with anywhere you search on the internet, about aluminum, copper, plastic tanks, all metal, you name it. The 2 row all metal I ordered, according to people on this forum who have used it say it fits perfectly, works great, and is only 130 shipped. I don't need overkill, I just wanted something solid.

Lastly, about the water pump; my original OEM pump lasted 110,000 miles. Before I started doing my own work, I took it to a mechanic to put in a new one, unknown brand... I now have 140,000 and am on my 4th water pump, and as you may guess I am back to an OEM one; no problems. I have a hard time believing your problem is only your water pump. RichP puts it simply, overheating on highway is a sign of bad radiator. If you think about it, the heater acts just like another small radiator, if your temp goes down with the heat on this likely means the radiator can't handle the load by itself.

One more thing, about the radiator flushes. I, along with others on this forum as far as I can tell, have had bad luck with the 10-15 minute idle flushes. On the other hand, I have used the 6 hour cleaners and those really get the crap out. It may be worth running one of those before putting in new equipment to be sure you get as much crap out of the engine block as you can.
Click to expand...

Thanks, already have a Mopar pump on hand (until recently there were 3 4.0L's in my family). And the Jeep has 105,000, so I figure it's water pump time anyway real soon.
 
I got a new radiator from partsamerica.com, it was like 150.00 or something, 2 year warranty (i think). I slapped that bad boy in and man, my temp went down. In MY opinion, anyone with a cherokee they do not know the history of completely, should do this. very cheap insurance, and your motor will love you for it. you can always get the locker later ;). Also, you don't need to go to a humongous aftermarket Modine 3 core or anything, i got an aluminum stock-style replacement one, and to date in 100+ degree heat i have yet to pass the 210 mark. Before, 210 was the norm.
 
OK the new rad and water pump are in. It now runs cool at speed (210 or less) but now it overheats around idle and in traffic. UGH.

I am going to do the fan clutch next, but I have a question about the electric fan too. Yesterday, I let the temp get up to about 230* at idle and the e fan did not kick on.

If you put the AC on, the fan comes on. Likewise, if you unplug the temperature sender by the thermostat housing, the fan kicks on. What could be mafunctioning so that it's not coming on by itself? Anyone know?
 
Nine Mile said:
OK the new rad and water pump are in. It now runs cool at speed (210 or less) but now it overheats around idle and in traffic. UGH.

I am going to do the fan clutch next, but I have a question about the electric fan too. Yesterday, I let the temp get up to about 230* at idle and the e fan did not kick on.

If you put the AC on, the fan comes on. Likewise, if you unplug the temperature sender by the thermostat housing, the fan kicks on. What could be mafunctioning so that it's not coming on by itself? Anyone know?
Click to expand...

could be faulty sending unit or relay
 
My e-fan kicks on around 220, give or take 2 degrees or so (if the a/c is off). This only happens after prolonged periods of idling or making a long uphill blast and then stopping completely at the top. It tends to stay on until the temp dips to around 200 or so. One thing I've noticed is that if the temperature is over 210 and I quickly flip the a/c on/off to turn on the fan, it will continue to stay on until the temp drops. You could try this when your temp gauge starts to go up and see if it stays on longer than about 7-8 seconds. If it doesn't, you can use a non-contact thermometer to hit the therm. housing and see if your gauge matches up very close to your reading to make sure the coolant sensor is accurate.

If the fan never turns on even when you're close to the red, I would definitely take a look at what Jess said above.

By the way, if you leave the a/c on does your temp stay at 210?

Also, I forgot to ask, did you have overheating at idle issues before you replaced the w/p and radiator? If this problem started afterwards, that will be important to consider.
 
Last edited:
Jess said:
could be faulty sending unit or relay
Click to expand...

If the relay was bad, would it still go on when I pull the sending unit wire off the thermo housing? I would think it would not, but I'm no electrical genius....
 
pauldo39 said:
By the way, if you leave the a/c on does your temp stay at 210?

Also, I forgot to ask, did you have overheating at idle issues before you replaced the w/p and radiator? If this problem started afterwards, that will be important to consider.
Click to expand...

Yes with AC on it stays at 210ish

And yes, it got warm at idle before too I am now being told. Half the problem is that it's not my vehicle (it's the GF's) so I have not been given all correct/complete information. It was actually getting hot both at speed and at idle before we started this whole thing.
 
Can anyone verify that for me?

If I pull the temp sender wire the fan goes on about 2 seconds later.

Does this mean the relay is good and that it must be the temp sender?
 
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