bigbearxj

So I purchased a 2000 XJ last year for cheap but it had a oil pressure issue which seems to have been caused by a 0331 cracked head. I purchased a remanufactured engine and replaced to motor last October.

Since then I have been battling a overheat problem any time the engine is under a load, going up a slight hill, on the trail, towing our tent trailer. It will rise to 230-240 like its nothing, one time the gauge spiked to 260 on a trail. Here are the facts of what i've tried. Happens at all ambient temperatures, I do live at 7,000 feet.

High temps have been confirmed with an infrared thermometer, however temps seem to be all over the place when thermometer is pointed at thermostat housing, up and down depending where you point it on the housing

1. 2 row aluminum radiator
3. Flowkooler water pump
3. Multiple new thermostats, now has a Robert Shaw 195 that is confirmed working
4. ZJ HD fan clutch
5. E-fan wire to switch, keep temp down around town but does nothing when under load
6. NEw A/C condensor, old one looked like it could be blocking flow but new one made no difference
7. Compression test was normal, 155-160 across all cylinders
8. Combustion leak test fluid did not turn yellow like is shown when there is a leak, however there was a VERY slight change in the blue fluid to a bluish green ??
9. Replaced Pre-Cats
10. Spring in bottom hose
11. Removed transmission cooler lines from radiator and installed separate cooler
12. Radiator cap, now has OEM cap on it and the hoses are pressurized while running

Im sure there is more. I am tired of throwing money at this thing trying to fix a mystery problem. I dont feel comfortable even driving it off the mountain anymore so it goes to work with the wife and thats it.

Please help! I want to drive this thing off a cliff!!

Thanks,

Daniel

timberwolf

That sounds like air trapped in there.

Is the water pump rotation correct?

bigbearxj

Yes sir, its a counterclockwise Flowkooler pump.

bigbearxj

Could a small combustion leak be causing the erratic temps with the infrared? As gases enter the cooling system maybe?

This year should self bleed the air out after a couple cycles, but the heating up under load continues after that.

Turbo X_J

Any codes? Have you removed the sparkplugs, are they pure white?

bigbearxj

No Codes. Plugs looked normal when pulled to do compression test.

kansas-klx

I agree about possible air trapped in system. Did any of your thermostats have about a 1/16" or so hole in the 12 o'clock position as installed? That will help any air pass to the radiator and then ultimately out to the overflow canister. I always drill my thermostat if I get one without the little hole. Mine is aftermarket, though. I think the OEM (mopar) ones have the hole already in them.

I have also found the best spot for me to use an IR thermometer on the thermostat housing is on the metal right where the upper hose attaches. Up real close, too, so that mech fan air doesn't disturb anything. Maybe its just consistency in measuring or the metal is thinner there and gives a best indication of coolant temp but that's where I've been doing it for a long time.

Hope you get it solved soon!

bigbearxj

The last two thermostats have have the bleed hole in them and seem to get the air out within a couple of cycles.

Turbo X_J

Reman motor has 0331 head too? Have you tried a cooling system pressure test to see if it holds? Do you have a scanner that can read live data?

bigbearxj

Yes the reman also has 0331 head. Have not tried the pressure test. The scanner I have will read some live data, what would I be wanting to look at?

Thanks

Turbo X_J

Timing, if it's too far advanced the motor will get hot real quick. Just an indication would help, you can't adjust the timing but will prove a faulty PCM.

bigbearxj

So I hooked up the scanner and timing was varying from 7-10 degrees advanced at idle and it to 33 degrees advanced at 1000-2000 rpms

Turbo X_J

Temps OK? If so, drive it under a condition to make it hot and have a passenger on board to watch the timing to see if goes haywire beforehand. I am guessing the only thing that has not been replaced is the PCM, correct? You can borrow a cooling system pressure test kit from Vatozone, pump up the system and see if it holds 16 lbs. If not there is a leak, do you notice a loss of coolant?

PocketsEmpty

Well there's your problem. You should've just swapped the head the first time with a different one (not 0331). I'm willing to bet the 0331 on your donor engine is no good either.

matiutoro

I HAVE THE EXSACT PROBLEM!!!!!
It's been 2 years now and replaced all hoses, 3 core aluminum champion radiator, water pump( counterclockwise wise) 160 thermostat, cooling system flush, external tranny cooler, and the 3 ten inch electric fan conversion. The only two more things I can think of is engine bypass cooling flush, and switching the stock water divergent thing on the heater hoses. If that don't work I WILL throw it off a cliff!!!