Potentially overheating 4.0, stumped and need help!

[onlyinajeep726]

***ISSUE RESOLVED!!!***

 

First off, let me say this is for a '95 XJ, so if the Comanche Gods (admins) wish to move this thread over to another sub-forum, feel free.

 

Okay, secondly, this may be a bit of a long post, but please bare with me as I try to explain all that's been done thus far in an attempt to rectify this issue...

 

About a month ago, I picked up another cheap-Jeep.  '95 XJ Sport for $300 in need of some strong TLC.  PO sold it because it was overheating, and suspected the head gasket. He had owned it/been driving it for just shy of three years, which was verified after looking over the title. First thing I did was check the oil, the radiator (which was empty except for a thick layer of rusty paste), and I peered down into the valve cover through the oil cap. Just a very basic diagnosis.  I agreed to buy it, and my buddy and I dragged it home.

 

I started by filling up the coolant system with water.  Started it and let it idle, and it went into the red-zone, so I shut it off. I noticed it was steaming from the back of the head.  Okay, PO was right  ...so I thought.  I removed the head, inspected the gasket (which had been replaced before at some point, not by the PO, so he claimed), and the gasket didn't show any signs of breakage or cause for concern.  I next cleaned up the head which was dirty, both inside and out.  Found a small pin hole in the freeze plug that I concluded was the cause of the leak.  No problem, I thought.  Flushed the head with a garden hose and some strong cleaning chemicals, popped a new freeze plug in and painted it for my own pleasure.  While I had the head off, I replaced all the valve stem seals and cleaned up all six intake valves as they were covered in a thick layer of carbon and burnt on oil.  Also, while the head was off, I removed the freeze plugs in the side of the block, flushed each coolant galley/port, and flushed through the side of the block, before replacing those five freeze plugs with new ones.

 

New M.L.S. Mahle/Victor Reinz head gasket, sprayed with Permatex Hi-temp Copper gasket spray, new head bolts, torqued down using the 3-step sequence specified by my Haynes repair manual, and I reassembled the manifolds, etc.  In addition to those new parts/gaskets, I've installed a new "high-flow" 195°F thermostat, water pump, new radiator (because the old one was assumed clogged or partially clogged from rust-paste), and new temperature sensor for the gauge (since I broke the original one removing the head... D'oh!).  Currently, I have the coolant system filled with Prestone coolant system flush and distilled water.  This is actually the second time it's been filled with that because the first time I filled it, I ran in and drained it to do an initial flush. It was quite dirty to say the least. Upon looking at the water/flush mixture, I see no signs of engine oil. It's just brown from what I assume is more rust that I couldn't get out via my garden hose flush.

 

Anyway, as it stands, it still overheats (or at least the gauge indicates it does). I have started it and let it idle for 20-30 minutes at a time once engine temp stabilizes, about 4-5 times now.  In each case, NOTHING leaks, no boiling over or steam, no white smoke from the tailpipe, no erratic running, misfire, or engine stumbling.  It idles perfect, revs fine, and shows no signs of ill fortune.  I even rented a coolant system pressure tester from AutoZone, pumped it up to 17-18 psi and left if pressurized over night, and the next morning it may have lost a half to one psi.  In addition, the electric fan is never triggered to come on, but if you turn the A/C on, it comes on like it's supposed to.  Also, out of curiosity to see if the factory temperature gauge is off, I swapped in another instrument cluster and the same thing happens.  I'd like to note, that in each time I've had it running for those 20 minutes or so, the factory gauge needle rests as the bottom end of the red-zone.  Oil pressure, if it matters in this case is damn near perfect at 40 psi at idle.

 

One thing I want to do is to check the engine, head, and coolant hoses with an infrared 'point-&-shoot' style temperature gauge to see what it's truly running at, but I don't have access to one at the moment.

 

So, what, if anything, am I missing?  Any suggestions or thoughts?  I know my way pretty well around these 4.0s, but this has me stumped and highly frustrated.

[Dzimm]

I would first try bypassing the heater core. There may be gunk coming from there causing problems. I had this happen in my 98 XJ, except it was not getting up to temp. I flushed it forward and backwards really good with a garden hose and a ton of gunk came out, then flushed the whole system again and problem solved. The next thing I would try is to replace the coolant temp sensors and inspect the wiring for them. With the needle resting at the edge of the gauge on 2 different gauge clusters, either this thing is running super super hot or there is an issue with the sensors/wiring.

[DesertRat1991]

Tell us more about the behavior of the temperature needle:

 

It sounds like the needle rises, then stops and holds steady at the bottom of the red zone?

 

You talk a lot about idling, what happens once you start moving?  Does the needle drop back down to nominal temp?  Hold steady at the elevated temp?  Or continue to rise? 

 

Also, what is the part number and source of the replacement temperature sender you bought?

 

 

 

 

 

 

 

 

 

[Green Mesa XJ]

I'm kind of wondering about the temperature senders, I think the 95 has two one for the pcm and one for the gauge

Sort of sounds like the guard sender is wrong or the parts house gave you a idiot light sender instead.

 

If they are correct for your xj then it sounds like something it gunked all to hell. If the PO tried the head gasket in a bottle then the radiator and heater core can be sealed up and just about anything and everything in between.

 

 

Sent from my iPhone using Tapatalk Pro

[onlyinajeep726]

I would first try bypassing the heater core. There may be gunk coming from there causing problems. I had this happen in my 98 XJ, except it was not getting up to temp. I flushed it forward and backwards really good with a garden hose and a ton of gunk came out, then flushed the whole system again and problem solved. The next thing I would try is to replace the coolant temp sensors and inspect the wiring for them. With the needle resting at the edge of the gauge on 2 different gauge clusters, either this thing is running super super hot or there is an issue with the sensors/wiring.

 

It's been flushed numerous times at this point.  Problem has been resolved, though.  It was a bad, new sending unit.  I replaced it with another, different brand and viola... Reads directly on 210.

 

Tell us more about the behavior of the temperature needle:

 

It sounds like the needle rises, then stops and holds steady at the bottom of the red zone?

 

You talk a lot about idling, what happens once you start moving?  Does the needle drop back down to nominal temp?  Hold steady at the elevated temp?  Or continue to rise? 

 

Also, what is the part number and source of the replacement temperature sender you bought?

 

It would hold steady no matter engine RPMs or under load.  The part number and brand of sensor that ended up being faulty was P/N: TU236 by Airtex/Wells.  The one that replaced it, that resolved my issue, was P/N: WT430 by BWD.

 

I'm kind of wondering about the temperature senders, I think the 95 has two one for the pcm and one for the gauge

Sort of sounds like the guard sender is wrong or the parts house gave you a idiot light sender instead.

 

If they are correct for your xj then it sounds like something it gunked all to hell. If the PO tried the head gasket in a bottle then the radiator and heater core can be sealed up and just about anything and everything in between.

 

 

Sent from my iPhone using Tapatalk Pro

 

I thought about that as a possibility, too.  Cross referenced the P/N and it all came back to being confirmed for the gauge style cluster.  Fortunately, it was replaced with a functioning one this evening and as a result, I'm quite the happy camper.

[Tex06]

Awesome, glad to hear you got it fixed!  I picked up a set of valve stem seals for my '92 a few weeks back, you wouldn't happen to have a write-up for the procedure would ya?  I use just a tiny bit of oil now and I'm thinking (with 213k on it) my original seals are probably shot.

[onlyinajeep726]

Awesome, glad to hear you got it fixed!  I picked up a set of valve stem seals for my '92 a few weeks back, you wouldn't happen to have a write-up for the procedure would ya?  I use just a tiny bit of oil now and I'm thinking (with 213k on it) my original seals are probably shot.

 

No, I actually don't have a write-up on it.  However, I did watch a video from NickInTimeFilms, seen here at the 7:48 mark.

https://youtu.be/mkrAG7gakPg?t=468

 

I also bought a valve spring compressor tool, seen in the above video.  Coincidentally, it's the same shown in the Haynes Repair manual that I also referenced.  This is it here: https://smile.amazon.com/gp/product/B000N322TG/

 

Lastly, the valve stem part numbers are as follows: Mahle/Victor Reinz B45798 (INTAKE valves) & Mahle/Victor Reinz B45799 (EXHAUST valves).

 

I'd like to note one thing.  If you don't want to remove the head, you don't have to.  They make a hose adapter that you can screw into the spark plug hole that pressurizes the cylinder with an air compressor.  It prevents the valves from dropping down into your cylinder.  I would also suggest manually turning the crank to where the cylinder you're working on is at TDC.  That should be double insurance.  Or, you could likely do it that way without the use of air pressure.  That air hose adapter is seen here: https://smile.amazon.com/Lisle-19700-Valve-Holder/dp/B000COC7ZU

[64 Cheyenne]

 

I'd like to note one thing.  If you don't want to remove the head, you don't have to.  They make a hose adapter that you can screw into the spark plug hole that pressurizes the cylinder with an air compressor.  It prevents the valves from dropping down into your cylinder.  I would also suggest manually turning the crank to where the cylinder you're working on is at TDC.  That should be double insurance.  Or, you could likely do it that way without the use of air pressure.  That air hose adapter is seen here: https://smile.amazon.com/Lisle-19700-Valve-Holder/dp/B000COC7ZU

 

 

Old guy showed me how to put rope/cord into the cylinder to hold the valve up, keep it from falling in. put the rope in, turn engine to move piston up, change spring seals or whatever pull rope back out when done.

[Minuit]

I also had a Wells temp sender read stupidly high. Gauge would read 225-240 when actual temp was around 200.

 

I'd rather have a 30 year old used Mopar part than some of the aftermarket $#!& out there these days. It's a thermistor, how hard can it be to make one read properly?

[HOrnbrod]

The part number and brand of sensor that ended up being faulty was P/N: TU236 by Airtex/Wells.  The one that replaced it, that resolved my issue, was P/N: WT430 by BWD.

 

More C.R.A.P. examples. I went through the same thing with "running hot" indications and it turned out to be the temp sensor. Two C.R.A.P. sensors in a row from two different C.R.A.P. manufacturers indicated false high readings on the gauge. Duralast and the O'Reillys junk counterpart IIRC. Nothing but OEM spares now for me. 

[Minuit]

BWD: Broken When Delivered. Pure C.R.A.P too, you must've gotten one of the rare good ones. I've been burned enough by their parts (especially EGR valves for some reason) to prefer a junkyard part over BWD.

[Tex06]

 

Awesome, glad to hear you got it fixed!  I picked up a set of valve stem seals for my '92 a few weeks back, you wouldn't happen to have a write-up for the procedure would ya?  I use just a tiny bit of oil now and I'm thinking (with 213k on it) my original seals are probably shot.

 

No, I actually don't have a write-up on it.  However, I did watch a video from NickInTimeFilms, seen here at the 7:48 mark.

https://youtu.be/mkrAG7gakPg?t=468

 

I also bought a valve spring compressor tool, seen in the above video.  Coincidentally, it's the same shown in the Haynes Repair manual that I also referenced.  This is it here: https://smile.amazon.com/gp/product/B000N322TG/

 

Lastly, the valve stem part numbers are as follows: Mahle/Victor Reinz B45798 (INTAKE valves) & Mahle/Victor Reinz B45799 (EXHAUST valves).

 

I'd like to note one thing.  If you don't want to remove the head, you don't have to.  They make a hose adapter that you can screw into the spark plug hole that pressurizes the cylinder with an air compressor.  It prevents the valves from dropping down into your cylinder.  I would also suggest manually turning the crank to where the cylinder you're working on is at TDC.  That should be double insurance.  Or, you could likely do it that way without the use of air pressure.  That air hose adapter is seen here: https://smile.amazon.com/Lisle-19700-Valve-Holder/dp/B000COC7ZU

 

 

Thanks!  I've got an old spark plug I saved to braze an air fitting to just for this purpose (did it before with a Chevy small block).  Just wanted to make sure the process was relatively the same.