Well my jeep wont stay cool.

1996 jeep cherokee 4.0. Ive only had it 2 weeks. The first week it ran perfect, then one day i noticed the temp gauge creeping up and got it home. Hoses felt swollen like thermostat was stuck changed it first no difference. Here we are now. Ive read all over forums and seen same symptoms but i cant cure it and not sure what else to try.

Things ive checked and replaced

New water pump
New radiator and cap
New stant 195 thermostat
New antifreeze
New thermostat housing
New fan clutch
New temp sensor in head
new belt/idler
Cleaned overflow tank

Flushed the head, block and heater core till they flowed clear
My heat works
My aux fan works

Ive tried burping air from radiator and temp sensor up on ramps

At idle it will run 230s and build pressure in radiator hoses till they are tight. But it seems too much pressure and not pulling or pushing any fluid into overflow, almost like low circulation or air. I haven't let it get hot enough to boil over. Running the heat or aux fan seem to keep it around 230 on the gauge but thats at idle any driving and it starts to creep up to 250+. Ive used a infared thermometer and shows 180 at housing at idle but driving makes it 220+ which seems fine but i can tell its hot it gets sluggish hoses really tight like air inside and it has steamed from the cap once when i got it to red. There is no water/oil mixing and overall it runs good until it gets too hot and throws a p0171 since i noticed a manifold crack at the collector. Could this be all the cause?

Sorry i rambled but i feel like im chasing a ghost. Thanks for any help!

Excess heat can come from a bad cooling system, which is what you have been addressing.

It can also come from a transmission that is slipping and thus running hot. There is a heat exchanger in the radiator that is used to cool transmission fluid.

The other thing can be an engine that is generating too much heat. The two most common things that cause that are a plugged cat (diagnose using a vacuum gauge) and running too lean. What color is the tailpipe? If it is white, you are probably running too lean. Running too lean can be caused by a large vacuum leak or by clogged injectors. Pull the plugs and post up pix and we can evaluate them for you.

A plugged cat will cause the vacuum to be too low because it can't suck air in to the engine if it can't blow it out the tailpipe.

Timing can cause over heating, but with a computer, it is pretty hard to screw up the timing.

It was just running perfect a week ago so no transmission slips, no odd tail pipe colors, no timing adjustments and no check engine lights. The engine runs perfectly normal and not until 250 degrees idling does it throw a lean code just in last day or so. I haven't been able to drive in several days. I considered a clogged cat but it hasn't given me any symptoms driving to believe its bad but i can check. Forgot to mentions theres no leaks im not loosing coolant anywhere.

96jeeper said:

It was just running perfect a week ago so no transmission slips, no odd tail pipe colors, no timing adjustments and no check engine lights. The engine runs perfectly normal and not until 250 degrees idling does it throw a lean code just in last day or so. I haven't been able to drive in several days. I considered a clogged cat but it hasn't given me any symptoms driving to believe its bad but i can check. Forgot to mentions theres no leaks im not loosing coolant anywhere.

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If you are throwing a lean code, you don't have a clogged CAT. I would start thinking about clogged injectors or a screwed up O2 sensor. Personally I would run a can of BG44 through the gas and see if it clears up.

I only get the lean code at 250+degrees from overheating i assume. Runs perfectly till then

Im considering doing a head gasket job anyway its only $60 for the felpro kit locally. 4.0 has 174k miles on the original gasket. Havent pulled the trigger on it tho because i have no signs of a bad gasket other than maybe excess pressure on radiator and hoses from poor flow?

Don't skip the obvious too, is it low on oil? Oil does a lot towards cooling the engine.

Any possibility the tstat was installed backwards?

What kind of radiator did you buy?

96jeeper said:

I only get the lean code at 250+degrees from overheating i assume. Runs perfectly till then

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If you are throwing a lean code, you don't have a clogged CAT even at high temps.

Some updates, still have not fixed this.
I changed the head gasket and tried another new water pump. Still no signs of coolant in oil or white smoke. Runs perfectly smooth and normal but temp is still going to red.

Did a compression test afterwards

1-150
2-140
3-150
4-160
5-145
6-150

This was with all plugs out coil and fuel un hooked.

Next was a coolant pressure test.

On a cold engine held 15-16psi for over an hour.

RedHeep said:

What kind of radiator did you buy?

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This is important. If you bought a cheap POS from Autozone like I did in a pinch, it could cause problems right out of the box, but nobody wants to suspect a new part.

I'm on my third Spectra. Once I buy a better radiator from a respectable manufacturer, I plan on giving the Spectra away.

It was only $110 or so.

Want to check the operation of the thermostat? Heater hoses will warm up first because the coolant flows around the thermostat. 195 is not far below the center mark on your gauge. Once the thermostat opens, the radiator hoses will warm up rapidly.

Your hoses are not swelling from lack of circulation, but from coolant expansion with temperature. It's normal to have pressure on the hoses at temperature. Remember the pressure rating on the cap? It's made to relieve excessive pressure. Up to that point is fine.

JohnX said:

Any possibility the tstat was installed backwards?

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If no then I would remove T-Stat and test it. Then you can always try a test by running the jeep with no stat in it, just for shits a giggles..

Sorry if I repeated anything but I didn't read all of this thread

I got the radiator from advance auto. But even the old one not leaking gave the same results I just ran it again this morning and it went up to 240 degrees. Both upper and lower hoses didnt really feel hot as they should i feel like they are full of air and cant really feel fluid in them. If its air i have no idea where its coming from and wont burp. I suspect a warped head but im not getting any water in oil or white smoke. Now the heater hoses get very hot and i can feel fluid in them. I have tested the thermostat on the stove and it opens at 195. I have removed the t-stat and ran it and got the same results. Have not had any more check engine lights and it runs smooth as ever. Just cant drive it.

Not sure if its ok to share links but heres where i started talking about the problem and have posted more test results
http://www.cherokeeforum.com/f2/well-my-jeep-wont-stay-cool-227727/

Sounds like an air bubble. Use an IR to read the temp at the thermostat housing.

Thermostat housing is around 175. Closer to 195 at the actual sensor. Gauge reads 240+ my obd scanner says 210. Why would the air not burp out or move at all? I have been goin through this for 2 weeks. Obviously by those readings youd think im not running hot. But that doesn't keep my gauge from going to red after driving and keep coolant in the overflow. Running with the cap off to maybe burp some air just makes it flow out the top of the radiator.

You are not actually running hot but the ecu is seeing a sensor that says so. There are only a couple of things that could cause it:

Like I said, an air bubble. Burping the system is a bit different for a renix vs an HO. A quick search should yield you tons of info. I actually do a vacuum burp but most don't have the tools for that.

You could have a defective temp sensor. Remember, there are more than one and on a Renix it is in the back of the head for the gauge. I don't remember on an HO, but they don't have the one in the head. IIRC the one on the themostat housing is to run the efan, but don't quote me on that. Most likely it is the one on the side of the block under the exhaust manifold.

You could have bad/corroded wire to the ECU.

You could have a bad ECU (not likely since it is actually giving you a temp).

Ok just started on a cold engine. Ran it up to temp. Gauge reads 240ish. Scan tool says 205. Infared at housing says 190-195. It seems to be acting better but i did drive it last night and it turned the aux fan on by itself and my obd scanner showed coolant up to 217 and more if i kept driving. Was also about to come out the overflow.

I have a 96 so i have the sensor in the back of the head and thermostat housing. I have changed to a new sensor in the head, have not changed the one in front but it does turn the fan on like it should.

Park down hill, loosen the sensor in the head until you get fluid running out, then screw it back in. That should take care of any air bubble. It is best to do this with a cool engine or risk getting scalded.

Until it gets the air bubble out, it is not uncommon to over flow a bit. As the air gets hot it expands, forcing out the coolant. Once the air is gone, this calms down.

So we may be onto a bad gauge/sensor. Hooked up the obd scanner and set live data for coolant temp. Started a trip to the store watched it climb to 160-170 degrees on the scanner even though the gauge inside said 215. By the time i reach the store the gauge says 240 but the scanner says 205 and holding. I then proceeded home. Gauge stayed at 240 and scanner at 205. Hop out pop the hood put the infared on the tstat housing it registers 190-200. Left it running for 15 mins and the numbers remained the same. no leaks or coolant backing into the bottle. Now given this was at night so the outside temp is upper 80s. Will test again tomorrow when its upper 90s.

Could i be looking at a bad temp sensor from autozone or a possible bad gauge?