Jeep coolant temperature help

[tsubaki]

I'd really appreciate some input on a 1996 Cherokee Classic 4WD with automatic transmission, AC and 4.0HO engine.
About mid summer I kept noticing the temperature gauge seemed to be reading a little higher than the normal 210 degrees while driving around town for brief 15 minute trips. But after about 30 minutes of intown or interstate driving the temperature would climb to about 230 degrees. Running with the AC on or off seemed to make no difference.
http://i175.photobucket.com/albums/w159/tsubaki3/jeeptemp.jpg
While sitting in the yard with the engine at 2000rpms, I can make the electric fan come on at about 235 degrees. As it also does when the AC is on.
I'm still having this problem with daytime high temperatures of 80 degrees and less. And there is no evidence of coolant contamination.

Here's a list of things replaced so far.
180 degree thermostat
Radiator
Catalytic converter, muffler and tail pipe
Fan clutch
Water pump
Temperature sending unit

Any ideas???

[spareparts]

have you actually put a thermometer or a heat gun on it to see if the temp is accurate?

[tsubaki]

No I haven't spare thanks, I might as well get one and see.
I figured since the electric fan comes on so close to the gauge reading it might be close.

[jasoncooperpcola]

Maybe you need to go to a lower temp thermostat?

[tsubaki]

It had a 195 degree in it for at least 2 years before the overheating indication and it stayed around 210 degrees.
Got the same vehicle but a year newer with a 180 thermostat and it stays at about 210.

[Destroyer]

Pull a compression test on your cylinders. These engines are just about bulletproof, but I've seen several of them with bad head gaskets. I had just about the same problem on my 98 Jeep Cherokee Sport. Turned out to be a bad head gasket between number 2 and number 3 cylinders. Fairly easy to replace, just a PITA.

[THEFERMANATOR]

Which sender or sensor did you replace? The fan should come on at 220 degrees according to the CTS. Have you pulled the radiator and cleaned out the condenser yet? As for the guage reading high, I can tell from your cluster it is a 96 or older JEEP, so it uses a sending unit mounted in the rear drivers side of the cylinder head for the temp guage. DO NOT run an aftermarket sender in one as it WILL be wrong. Also the CTS(coolant temp sensor) will be mounted in the T-stat housing if it is a 91-96, and ONLY run an OEM here as well(can't tell you how many aftermarkets have caused me grief over the years as GM and CHYRYSLER both used the same appearing CTS but with different resistance readings, and teh afterm,arket ones get mixed up ALOT). If it is a 87-90 it will be mounted in the lower ceneter portion drivers side of the block, but they use a fan switch mounted in the radiator to turn the fan on and off. Put in a OEM t-stat back in it as a lower temp t-stat does NOT stop overheating, all it does is create OTHER problems like check engine lights, washed down cylinders, poor cabin heat, and only accomplishes making it take a little longer before it overheats. These engines LIKE to run at 200-205, which happens to be the ragged edge of overheating.

Head gaskets do fail on these, but normally once they get run hot and the head gaskets go the rings break in them from it. I've pulled the head and done head gaskets to many times now and had to pull em back down to do rings to do just a head gasket anymore. Head gaskets are pretty easy to diagnose though as when they go you either get teh white smoke and coolant smell out the tailpipe, or the reservoir bottle will overflow.

Let me know if you have any specific questions as I used to eat, sleep, and breath JEEPS before I went diesel crazy. I was even a JEEP tech at a dealer, and was dam good at em. I would pull the radiator back out though if it was mine, and CLEAN teh condenser out REALLY good. This is a HUGE problem area in the JEEPS and often overlooked. Also make sure you got a max cooling radiator. I have had problems with the brass cored units fro mADVANCE, and have had good luck with the aluminum cored ones from AZ. And put a factory sender back in the rear of the head. Your description though sure sounds like air blockage to the radiator.

[THEFERMANATOR]

Maybe you need to go to a lower temp thermostat?


Lower temp t-stats NEVER stop overheating, it ONLY makes it take longer to overheat.

[tsubaki]

Thanks FERM, the sensor I replaced is the one at the rear drivers side that disabled the temperature gauge when disconnected. The one at the thermostat housing initiated the electric fan and set off the check engine light when disconnected.
New radiator and no build up in the old one, replaced it anyway. The condenser does have a few flat fins and a fair amount of gravel lodged in it but I can see through a very high percentage of it to the radiator.
This animal has never lost coolant or gave any of the normal overheat indications except for the gauge.
I'm aware of the air blockage especially on the ones that have the funny looking tank. This one has the regular old overflow type.
My next thought was to replace the condenser, basically because of the elimination process order I've replaced prior. Then pull the head and replace the gasket if that don't help.
First I'm gonna do like spare suggested and see if I can determine if the gauge is close to correct.
Keep throwing this stuff this way please!

[THEFERMANATOR]

Thanks FERM, the sensor I replaced is the one at the rear drivers side that disabled the temperature gauge when disconnected. The one at the thermostat housing initiated the electric fan and set off the check engine light when disconnected.
New radiator and no build up in the old one, replaced it anyway. The condenser does have a few flat fins and a fair amount of gravel lodged in it but I can see through a very high percentage of it to the radiator.
This animal has never lost coolant or gave any of the normal overheat indications except for the gauge.
I'm aware of the air blockage especially on the ones that have the funny looking tank. This one has the regular old overflow type.
My next thought was to replace the condenser, basically because of the elimination process order I've replaced prior. Then pull the head and replace the gasket if that don't help.
First I'm gonna do like spare suggested and see if I can determine if the gauge is close to correct.
Keep throwing this stuff this way please!

I would start by going to Chrysler and buying BOTH the coolant temp sensor(one in the t-stat housing), and the sending unit(one in the rear of the head). Eliminate those two from the equation. I cannot stress enough to not use aftermarket parts for the electrical if you don't want to deal with grief just like this. And if there is any debris to speak of in the condenser, it will run hot. Also put in a factory OEM t-stat from Chrysler while you are doign the CTS and sender. It will be a hotter t-stat, but they work much better. I've had alot of problems with aftermnarkets here lately hanging until 225-230 before they open, and then plummet down and work like they are supposed to.

[tsubaki]

Would you believe it was the MAP sensor causing the problem all along and there were no fault codes to indicate such?
I now have 3 OBDII readers and a temperature gun in the stock pile, the first two OBDII readers would not link up to the computer. I accidentally found/purchased the third reader and it confirmed the overheating.
For the meanness of it I replaced the MAP sensor and after a week of driving and a tank of gas the gauge never got over 205°.

[tsubaki]

And yes I realize this thread is over a year old.
I've been fighting this thing since August 2012!
And FERM the fan would come on at 221.9°, so you were dead on the money!

[randlemanboater]

Glad you were finally able to fix it...if you are like me, stuff like that can drive you crazy until you figure it out.

[Destroyer]

Congrats Tsubaki.. It's been a long hard fight I'm sure. Glad you came out the winner. Now it's miller time!! :happy:

[spareparts]

MAP sensor? Was it running rich or lean? it doesn't make sense to me, but whatever works

[THEFERMANATOR]

Jeeps run lean to begin with for emissions reasons. If the MAP was far enough off it can push stoic up to around 15.5-16:1 which would lean it out big time. Never heard of one doing it at idle unless for some reason it wasn't going into closed loop.

[tsubaki]

I actually argued with my father that it was not possible to be the problem. His response was "you done replaced everything else, it's going to be a lot easier changing it instead of replacing the head gasket or timing chain".
The live data stream from the code reader showed the timing jumping all over the place after it got warmed up, I was convinced the timing chain was stretched slightly.
Glad I was wrong and did like Daddy said.

[THEFERMANATOR]

I actually argued with my father that it was not possible to be the problem. His response was "you done replaced everything else, it's going to be a lot easier changing it instead of replacing the head gasket or timing chain".
The live data stream from the code reader showed the timing jumping all over the place after it got warmed up, I was convinced the timing chain was stretched slightly.
Glad I was wrong and did like Daddy said.

The timing chain would have no effect on the timing. The timing is based off of the crank sensor, and only uses the sensor in the distributor as a sync signal to tell it when it is at TDC on #1 for fuel injection.

[bradford]

Slightly off topic, but Tsubaki I have a 1997 Grand Cherokee my brother in law and I are gonna be parting out if you need any parts. 4.0 engine, 4x4, automatic, black exterior.

[tsubaki]

Thanks bradford, those parts are getting scarce and should command a premium.

[THEFERMANATOR]

I've got a 97 4.0L out of a CHEROKEE that has about 70K miles on it, and I can't give the dam thing away. Tried with a few people and everybody laughed at me. Things hardly ever blow an engine unless you run one hot.

[Destroyer]

I've got a 97 4.0L out of a CHEROKEE that has about 70K miles on it, and I can't give the dam thing away. Tried with a few people and everybody laughed at me. Things hardly ever blow an engine unless you run one hot.

Ferm, I just might need that engine. My 98 Cherokee ran super hot due to loss of coolant, and now it has low compression in 3 cylinders. (2,3, and 5) I know it;s my own damn fault for running it hot, but I was in a bad spot on the freeway and really didn't have a choice. Anyways I suspect a blown head gasket caused the initial coolant loss. I won't know till the spring when it's warm enough to work on it outside what the total damage is. I'm thinking a head gasket and probably broken rings. But if it's anything more than that a transplant may be necessary.

[THEFERMANATOR]

Ferm, I just might need that engine. My 98 Cherokee ran super hot due to loss of coolant, and now it has low compression in 3 cylinders. (2,3, and 5) I know it;s my own damn fault for running it hot, but I was in a bad spot on the freeway and really didn't have a choice. Anyways I suspect a blown head gasket caused the initial coolant loss. I won't know till the spring when it's warm enough to work on it outside what the total damage is. I'm thinking a head gasket and probably broken rings. But if it's anything more than that a transplant may be necessary.

Yep, sounds like some broken rings. Problem is the newer 96+ metric hyperautic pistons seem to crack a lot more so than the early style cast pistons did when run hot. I've scrapped out a few, and the 96+ engines seem to have cracked pistons in them when run hot whereas the early cast pistons would be fine.

[Destroyer]

Yep, sounds like some broken rings. Problem is the newer 96+ metric hyperautic pistons seem to crack a lot more so than the early style cast pistons did when run hot. I've scrapped out a few, and the 96+ engines seem to have cracked pistons in them when run hot whereas the early cast pistons would be fine.

Ugh. Never thought about cracked pistons. Figured that since I still had compression of 75 and above on the bad cylinders that I had not melted a hole in them... One more thing to look at. Still, with the pistons out to look at the rings replacing the piston itself should not be a problem.

Now it gets down to the "do I do the necessary work on the present engine or do I do a transplant?" question. <sigh>

[THEFERMANATOR]

Ugh. Never thought about cracked pistons. Figured that since I still had compression of 75 and above on the bad cylinders that I had not melted a hole in them... One more thing to look at. Still, with the pistons out to look at the rings replacing the piston itself should not be a problem.

Now it gets down to the "do I do the necessary work on the present engine or do I do a transplant?" question. <sigh>

The 96+ engines I had would crack between the ring lands when run hot. And you need the special fixture to change them out. The pistons where the rods go in is angled but the rods are flat, so you have to have the tool to hold the rod to press them out. 87-95 engines were flat in the piston where the rod went, and the rods were flat so you could just support the piston and press them apart. Just one more reason I like the 91-95 engines. Now if you find a 93-94 grand Cherokee short block to drop in, you will have a screamer on your hands. 93-94 grand Cherokees had a much more radical duration to the camshaft and held the valves open longer. 96+ engines made there power with hotter tuning, 91-95 engines did it with a better cam. Put a 91-95 cam in a 96+ truck and you will notice a difference. I put a 93 cam in my 88 and it woke it right up. Put one in a 96 and that sucker flat out MOVED! Then again these were just budget builds because I had the 93-94 grand Cherokee cams in the shop.

[smokeonthewater]

hmmmm sooo a 93-94 grand cherokar cam in my 95 YJ w 230k miles.....

[smokeonthewater]

WHOOPS just realized you gotta pull the head to get to the lifters!... UGH I wish I had that free 70k engine to swap in with a new comp cam n a couple other goodies

ever get near Louisville? :D

[Destroyer]

The 96+ engines I had would crack between the ring lands when run hot. And you need the special fixture to change them out. The pistons where the rods go in is angled but the rods are flat, so you have to have the tool to hold the rod to press them out. 87-95 engines were flat in the piston where the rod went, and the rods were flat so you could just support the piston and press them apart. Just one more reason I like the 91-95 engines. Now if you find a 93-94 grand Cherokee short block to drop in, you will have a screamer on your hands. 93-94 grand Cherokees had a much more radical duration to the camshaft and held the valves open longer. 96+ engines made there power with hotter tuning, 91-95 engines did it with a better cam. Put a 91-95 cam in a 96+ truck and you will notice a difference. I put a 93 cam in my 88 and it woke it right up. Put one in a 96 and that sucker flat out MOVED! Then again these were just budget builds because I had the 93-94 grand Cherokee cams in the shop.

Well, hopefully I'll just find some cracked rings and that will be the end of it. If I have to press out the wristpins I'll talk to one of my friends who works for Chrysler and see if he has the tool that I can borrow. Or if it's really damaged I'll say the hell with it and go the transplant route. I know this guy that has a 97 4L engine with about 70K on it that he can't give away.... And I'm thinking I can buy it from him. Only problem is I'll have to drive to Fla to get it.. but I've done that before so it's no big deal.