XJ 4.0 overheating

2pwrlftrs4u · Aug 4, 2008

during our trip our XJ starting overheating. so far what i have done:

replaced the fan clutch (OEM)
flushed the system, new coolant and added water wetter (royal purple)
new (OEM) radiator also added tranny cooler
high flow 180* thermastat

still overheating but not near as bad as before, now its running about 230* mid-day

here's what i am considering as options...

high flow thermastat housing
high flow water pump
buy a higher quality radiator

any suggestions before i shell out the money for a better radiator and high flow water pump??? i also posted the question on NAXJA

thanks in advance

NotMatt · Aug 4, 2008

What year?

2pwrlftrs4u · Aug 4, 2008

NotMatt said:
What year?

'96 auto tranny

Mudmayhem101 · Aug 4, 2008

Have you checked the water pump?..Maybe corroded Internal fins Or a fualty reading, have you verfied temp with a external device ( such as a temp gun..?)....

Not Jobless · Aug 4, 2008

You seem to be throwing a lot of parts and dollwars at it...

Have you checked:

1. Radiator cap
2. Pressure tested the system
3. #2 may help diagnos a water pump problem as well

I seem to remember Jeff's old 4.0L cherokee having problems like this and it was associated with the "closed" overflow system but can't be 100% sure.

Mudmayhem101 · Aug 4, 2008

I moved from the south (Florida Panhandle)to Washington state. I Work as a Master Auto tech. I saw aLot of cracked heads on the 4.0's mostly up to about 2000 models then they kinda stopped for some reason, maybe a design change. Usually they would have very small cracks, hard to see with the eye even. Usually would be found by the machine shop, when the head was pressure checked. Usually would pass a pressure check in the vehicle, prob. has something to do with temp. vs pressure... Well good luck, just my 2 cents.

gasman1 · Aug 4, 2008

I know my jeep runs a little hotter with an external radiator cooler on a stock radiator.

Most stock radiators have a single tube, if you block the air flow with an external tranny cooler it may not cool down enough.

Some thing to consider, my .02

1 grumpy · Aug 4, 2008

Does it have the electric fan by the clutchfan?And I put hood vent's on my 91 I-6 and it helped with the overheating a bit.easyer air flow.

NotMatt · Aug 4, 2008

Band-aid and high dollar fixes include "high flow" water pumps and t-stats, lower temp t-stats, water wetter type products, hood spacers, t-stat removal, etc etc are all just masking an underlying problem. The factory system is a good design and worked great off the showroom floor, even with a stock-sized radiator, integrated tranny cooler, and "stock flow" water pump.

I would check Jobless's suggestions.

My understanding of cooling systems leads me to believe that a "high flow" water pump, thermostat, or a completely removed thermostat would actually make no improvement in cooling, or possibly even make things run hotter. The reasoning behind this is that the coolant is moving faster through the system, giving it less time to absorb heat from the engine components, and/or less time in the radiator disapating heat. That's my wild-ass theory that may or may not be backed up by science.

I had an '87 cherokee with the stock closed cooling system, new stock temp t-stat, stock fan clutch, and a stock replacement all metal radiator from Radiator Barn. It ran rock solid at 210 in the worst/hottest conditions ever with no hood spacers, no vents, no high flow pumps, no water wetter, no electric fan toggles.

okeedokee · Aug 4, 2008

Have you been in the mud you might want to clean your radeator if you been wheeling in mud it tend to build up alot

TreeClimber · Aug 4, 2008

Some Jeep Cherokees had a radiator that didn't have the cap on the radiator, but rather on the coolant overflow resevour. That style system was prone to cracking the plastic of the overflow tank, resulting in an un-pressurized system. Since a pressurized system will run cooler than a non-pressurized system, it would follow suit that the running temp would also be hotter.

I'd start with some basic diagnosis Kyle. Get a quality pressure tester and test the coolant system for a pressure leak. A blown head gasket could also show up here (but not necessarily). Then do a leakdown test on the cylinders to further look for a head gasket issue.

Also, when the engine is at operating temp, have someone double check the dash guage with a temp gun. You may have a bad guage or sender, and actually be at the correct operating temp.

Good luck, and post up the progress updates.

Tony

NotMatt · Aug 5, 2008

TreeClimber said:
Some Jeep Cherokees had a radiator that didn't have the cap on the radiator, but rather on the coolant overflow resevour. That style system was prone to cracking the plastic of the overflow tank, resulting in an un-pressurized system.

For clarification, that would be the '90 and older models. '91 and newer changed over to a standard "open" style system with a rad. cap on the radiator and a regular overflow bottle.

There's nothing terribly wrong with the closed system, other than the mentioned problem about the bottle cracking (had it happen on my '87), and the fact that it's harder to fill and bleed air out of. Some people convert the older ones to the newer open style when changing radiators out.

For the purpose of this thread, it's moot though... as a '96 has the open system.

2pwrlftrs4u · Aug 6, 2008

TreeClimber said:
Some Jeep Cherokees had a radiator that didn't have the cap on the radiator, but rather on the coolant overflow resevour. That style system was prone to cracking the plastic of the overflow tank, resulting in an un-pressurized system. Since a pressurized system will run cooler than a non-pressurized system, it would follow suit that the running temp would also be hotter.

I'd start with some basic diagnosis Kyle. Get a quality pressure tester and test the coolant system for a pressure leak. A blown head gasket could also show up here (but not necessarily). Then do a leakdown test on the cylinders to further look for a head gasket issue.

Also, when the engine is at operating temp, have someone double check the dash guage with a temp gun. You may have a bad guage or sender, and actually be at the correct operating temp.

Good luck, and post up the progress updates.

Tony