97 XJ overheating - EVERYTHING IS NEW!!

[Camo-5]

OMG. I'm about ready to kick the XJ to the curb.

Since my last post, I've replaced the theromostat with a high flow 180 deg and cleaned out the thermostat housing for better flow. I also though my fan spun suprisingly easy while the engine was registering 250 deg, so I replaced the fan clutch, again. Still no go. It overheats as soon as I turn the A/C or any load is applied (I was jump starting my 79 Cherokee when the check engine light came on). I keep getting the same flash boil effect. it hits about 220ish then flashes and jumps to 250. If I shut it off, it pukes steam / fluid back into the reservior. I really don't want to start throwing money at it with new parts (already stared doing that). I just don't know what to do. I would suspect the rad wasn't sufficient, but it started this before I changed the rad.

 

[heyhar]

Seven years ago, I pulled the head off my '92, at about 130k, to replace the lifters. While everything was apart, I cleaned as much carbon and gunk as I could. One thing that surprised me was that the rearmost coolant passage was almost completely clogged with what appeared to be dried or coked-up antifreeze, same green color. Both the head and block side of the passage was affected. The vehicle did run warm (the A/C worked back then), but didn't overheat. Once everything was cleaned and re-assembled, it ran noticeably cooler (and quieter, thanks to the new lifters!). I realize that pulling a head is a bit extreme, but if all the external parts are newer and above question, possibly it's time to look for internal blockage.

 

[joe_peters]

What mix coolant? 50/50 is a year round compromise, better as an anti-freeze than a coolant. Cut the mix to 30 ethylene glycol and 70 distilled water.

You can eliminate the heater core as a suspect--short length of heater hose and two clamps, thermostat housing outlet to water pump return.

HAVE you tested for combustion gasses in the coolant--rent the tester and purchase the chemicals.

I believe you mentioned that you replaced the fan clutch--did you consider an upgrade to a ZJ HD fan clutch, NAPA 272310, $44.

Fan clutch testing:

From the 90 FSM:

"The cooling system must be in good condition prior to performing the test outlined below to ensure against excessively high coolant temperature.

CAUTION: Ensure that there is adequate fan blade clearance before drilling.
(1) Drill a 3.18 mm (1/8 in) diameter hole in the top center of the fan shroud.
(2) Insert a dial thermometer -18 degree to 105 degree C (0 degree to 220 degree F) with an 8 inch stem, or equivalent, through the hole in the shroud. Ensure that there is adequate clearance from the fan blades.
(3) Connect a tachometer and an engine ignition timing light (to be used as a strobe light).
(4) Block the air flow through the radiator by securing a sheet of plastic in front of the radiator (or air conditioning condenser). Use tape a the top to secure the plastic and ensure that the air flow is blocked.
(5) Ensure that the air conditioner, if equipped, is turned off.
WARNING: USE EXTREME CAUTION WHEN THE ENGINE IS OPERATING. DO NOT STAND IN DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE PULLEYS, BELTS, OR FAN. DO NOT WEAR LOOSE CLOTHING.
(6) Start the engine and operate at 2400 rpm with the timing light (strobe light) aimed at the fan blades. Within ten minutes the air temperature (indicated on the dial thermometer) should be 88 degrees C (190 degrees F). Satisfactory operation of the fan drive requires that it engage before or at 88 degree C (190 degree F). Engagement is distinguishable by a definite increase in the flow noise. The timing light will also indicate an increase in the speed of the fan.
(7) When the air temperature reaches 88 degrees C (190 degrees F) remove the plastic sheet. Satisfactory operation of the viscous fan requires the air temperature to drop 20 degrees F (11 degrees C) or more. A definite decrease of audible fan air flow noise should be noticed. Replace defective fan assemblies."

 

[bchulett]

Thanks for all the good suggestions. I guess I should have laid out a timeline for the symptoms and repairs.

I replaced the rad (2 core HD alluminum) since it had over 200K on it and the alternator was original so I replaced that also - still no change.

curious... I didn't know XJs came with an aluminum radiator. When my 1991 started doing this, I replaced my Factory HD 3 core brass tank model, with the Factory HD 3 core plastic tank model.

This is the OEM radiator that comes with the HD towing package.. it was expensive, but worth it.

Also, I have a factory trans cooler that bypasses the radiator.

Not sure what your problem is... 2 core isn't very robust.

Check your viscous clutch fan?

.

 

[carves]

curious... I didn't know XJs came with an aluminum radiator. When my 1991 started doing this, I replaced my Factory HD 3 core brass tank model, with the Factory HD 3 core plastic tank model.

This is the OEM radiator that comes with the HD towing package.. it was expensive, but worth it.

Also, I have a factory trans cooler that bypasses the radiator.

Not sure what your problem is... 2 core isn't very robust.

Check your viscous clutch fan?

.

I think this is what adds to some of the "overheating" confusion on threads.

The XJ was available with several radiator types ... and therefore some owners will have no cooling issues and others will ... especially if, as a repair/maintenance - the basic radiator ( OE or aftermarket ) is fitted in locations that require a heavier duty radiator.

In regards to 2core radiators ... A quality one is quite sufficient - IF the design, tubes sizes etc., are right.

 

[bchulett]

I think this is what adds to some of the "overheating" confusion on threads.

The XJ was available with several radiator types ... and therefore some owners will have no cooling issues and others will ... especially if, as a repair/maintenance - the basic radiator ( OE or aftermarket ) is fitted in locations that require a heavier duty radiator.

In regards to 2core radiators ... A quality one is quite sufficient - IF the design, tubes sizes etc., are right.

Agreed.. actually you can scratch my post above. It's been five years since I replaced my OEM radiator... I research this to no end and found that Modine was the OEM manufacturer for Chrysler - I talked to a Modine engineer about this.

I can't recall the specifics, at the time all I knew was everyone was installing 3 row GDIs.. I went with the factory replacement and as indicated in my post is an aluminum two row.

I had to hunt this down .. here's my original post in 2005.

http://www.naxja.org/forum/showpost.php?p=387695&postcount=7

.

 

[Camo-5]

One thing that surprised me was that the rearmost coolant passage was almost completely clogged with what appeared to be dried or coked-up antifreeze, same green color

Would a power flush bust this out? I just find it odd that it only overheats when under a load. I could drive all day long in 100 deg weather at 40 mph and never his 220 on the temp gauge. As soon as I hit highway speeds or turn on the A/C, the temps slowly climbs until it flashes.

Is there a way to test coolant flow?

 

[ParadiseXJ]

Is there a way to test coolant flow?

Yes. If you already put a flush tee in the heater hose, just take the top off and start the engine...or...take the return hose off the t-stat housing...same deal.

Wrong pump could be the culprit, or incorrect belt routing, or clogged core.

After everything you've done that's about all you have left for hiway speed overheating.

 

[Nickfast]

I know I am late to the table, but I REALLY think you need to verify what the ACTUAL temp is.
You could have a guage or wiring fault that spikes the reading as the guage cluster voltage goes up with increasing RPM....especially since you state that it runs well.
Does it act like it's getting too hot? Yoy should have a noticeable loss in power as well as pinging if it is actually getting as warm as your guage says.
Find some place to plumb in a mechanical guage (if nothing els, pull a block plug), and even if it's a cheap guage, it will tell clear up what's going on.

Nick

 

[Camo-5]

Since the coolant / steam is spewing back into the reservior, I'm pretty sure it's running too hot.

Also, I'm running 30 coolant / 70 H20.

I'm going to test for gases in the coolant. Could I actually have a bad head gasket or cracked head or block for almost 2 years with no other sign other than overheating in hot weather? Seems oddd....but I've seen stranger.

 

[Speedbump96]

i would change out ur fan clutch with a hd one i had the same problem put a new fan clutch on and it brought the temp down quite a bit

 

[Samson04]

A friend of mine has a 98xj 4.0 and a couple of years ago had some very similar symptoms as you are having. Only running hot at highway speeds, new everything on the coolant system. His problem ended up being the water pump. Apparently, they gave him the wrong one when purchased, the fins on the pump were hitting the inside of the water jacket, caused them to break off. It would still run at 210 sitting at an idle and even at slower speeds, but at highway speeds and under a load it would overheat. Just a thought.

 

[sanjuanxj]

Ditto on the water pump. You've got to compare your old pump with the new pump for clearance and fan rotation-happend to me once.

Could it be a problem with exhaust? The OE exhaust manifold is notorious for not being very effecient at getting the hot exhaust gas out quick enough. About 6 years ago, I pulled the head off my '96, had it milled and replaced the exhaust manifold with a Banks. I've not had a single heating/cooling issue since this was done. - just a thought.

 

[Camo-5]

Hmmm......I'm going to pressure test the system tomorrow to confirm that i have no leaks. If all checks out, I'm going to replace the water pump. I can't imagine it was the wrong once since it's been in there for 30,000+ miles and the problem just started about 5,000 miles ago, but who knows. The cheapo crap they make now adays, maybe it wore out already. If the pump doesn't fix it, I will take a look at the exhaust.

Thanks for all the suggestions. I'm running out of options!!!