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having overheating issues. 94

Dragonlich1961

NAXJA Forum User
Location
Ohio
my 94 4.0 aw4 is having bad overheating issues.
idles with hood up and ac on 12 220-230. driving around the block with no real stopping and the guages is close to red. i know these things run hot.
I've installed a mishimoto rad, b&m trans and p/s coolers, Removed my winch to promote air flow, high flow tstat housing and high flow water pump. all over a year ago. ( all but winch). and it cooled fine little warm but it's a jeep xj. I simply can not run ac in anything over 75 degrees. and even at 90 with no ac it runs 215-230. not good.
Onlything i can find is i have no noticable coolant leak yet i do have to add alittle bit every now and again. Am i right to suspect a head gasket?
 
Hi,

Some more basic things I can think of first would be:

Did you change your fan clutch? Is your electric fan working? Did you test or change your radiator cap?

Does it run hot at highway speeds too?

Patrick
 
Fan clutch and rad cap about one year old. Fan clutch when warm has drag and stops spinning shortly after you remove your hand. So it's good.
 
Does it run hot on highway too?

How much coolant do you add after x amount of miles?

Maybe time for at least a compression test or leak down test.
 
Highway driving is bad. 70. Is Max any more and it will run hot. Coolant is maybe a resivour full every 500-800. Not been paying to much attention.
Before the new radiator went it I flushed the block and heater core. Then did water pump and tsat after, so the block it flushed as much as possible. I know these rigs suck at maintaining engine temp. But I'm not asking it to do anything extrodinary here.
Rig is a 94 168k aw4 bout 5 iinchs lift with 33 4.56. stand alone b&m cooler stacked plate style,. Biggest that will fit in front of mechanical fan. With same cooler for ps. Radiator trans cooler not plumbed.
Ac works great.
 
Not normal for it to be overheating at highway speeds. My XJ only starts to get hot on uphill climbs but that's fairly normal as it cools back down rapidly.

That's a lot of coolant loss.

Unless you have a easier leak you haven't found such as a hose, defective water pump (underside from weep hole), freeze plug, thermostat housing (underside), heater core (coolant smell inside cabin), etc it sure sounds like it could be cylinder head related.

Have a good look around after 10 min of shutting down. If you can't find any leaks you have to do some further testing with the correct tools.
 
Changed out the head gasket about an week ago, found possible coolant issues in cylinder five. it was only slightly cleaner then the rest. STILL having heat issues, and it's starting to get warmer. changing out the head gasket has resulted in coolant not leaking from every hose clamp conecntion, so i think it was a small problem but oviuosly I've still got something wrong.
It runs hot at idle, and running down the road, just today at 55-60 degrees it hit close to 230 no ac while driving.
Mishimoto Rad, stock e fan(unreplced original), stock clutch fan (Replaced), high flow pump (flow kool), high flow t-stat housing (hesco), 195 t-stat (stant). All hard cooling parts installed in may/june of 18, after flushing system. i have driven it to work and back every day(one week), no coolant loss, even ran the vehicle on lift with coolant funnel and front lifted to remove air, no change.
 
Have you verified that you're not running lean, and O2 sensor is working correctly? Tried going back to a stock thermostat housing and pump? Did you read the thread I posted about problems with the hi-flow stuff, and that the poster solved it by plugging off the hose to the heater core?
 
Sorry to hear you are still having overheating issues.

Seems pretty serious. Maybe try borrow/rent a leak down tester?

What about a blockage? I guess you've checked but maybe defective thermostat or water pump?

Have you started up without the radiator cap on and watch the water flow/temperature as it heats up?

Top radiator hose should start to warm up and you should start to see flow in the radiator. Water level should gradually go up and your temp gauge needle should show at about 1/4. Once the thermostat opens you should see a brief temp drop and after that probably will have to put the radiator cap back on.

That will help purge air out too.

On a side note I had success in getting the XJ cooling working tops by changing out the sender at the thermostat housing. It was failing for a while and I eventually noticed because it got worse and electric fan would not come on.

Keep up posted.
 
Check for an exhaust leak at the exhaust manifold collector. A long time ago I had a leak there, the donut gasket was bad and the hot exhaust was blowing on the block. Made everything heat up and ran super hot.
 
I have been trying diffrent size restricters over the week, and have had no luck. Seams like it does ok staying cool until extra heat is added, then it simply can not disapate it.
engine temps slowly rise on the 30 mile 1 hour drive to and from work. average speed is 55-60. Jeep has 33 and 4.56, 60 degrees on way home, and by 55 mins in the engnine wanted to sit comfotably around 230 ish. crusiing or idle.
i have tried a 1/2 hole and 5/8 hole, as well as a heater core resrictor. 1/2 did an ok job keeping it cool for first half of drive, but resulted in huge temp swings at idle. like no ac up to 220, but would cool down when moving, right up until i hit sustained periods of 65 and temp would rise and not come back done. trans temps are at 190-200 using sensor port in trans, this repetativly sees 220+ during summer. this is with a B&M 70264 14,400 btu cooler. cooler is located on Right side( mechanical fan). No factory cooler/ by passed. Am i possibly fighting a slipping trans. Last time i did a flush( machine flush) fluid look like crap, very dark and burned smell, and it maybe had 20-30k. Left side (e fan) has same cooler for PS. Winch is removed to premote airflow.
 
Seems like there's something serious wrong with your cooling system.
Basic checks:
A bad thermostat or installed wrong.
Coolant system not burped.
Fan shroud missing.
Water pump defective.
Bugs and debri clogging up both the AC and engine radiators.

If misery loves company i had the same issue but not as bad with my 2k especially running the air in stop 'n traffic. Also NOT running the air while idling in the McDee drive thru all in hot Summer weather.

My solution was to jury rig the electric fan to turn on at will via a PB switch to turn on a 5 min. timer.
 
cooling system was burped with a coolant funnel, I even ran it on a rack with the front only lifted. Both fan shrouds are pressent, small crack in mechanical but is still one peice. e fan has a broken mount for the motor so the fan motor moves around(just discovered) so it will be replaced soon, but it still functions and pulls air. I till also try a new thermostat this weekend if time pemits.

I can engineer a cooling system to cool a 350 hp smallblock, and i can't get a bone stock glorified tractor engine to stay cool in 60 degree weather. grrrr
 
I had similar problems with temp creep, replaced everything a couple of times, finally fixed it with timing chain replacement. The old chain was stretched enough so that exhaust valves were keeping combustion gasses in the head.

Also, flush the heater core and control valve, that circuit is critical to keeping the temps normalized
 
Heater core was replaced recently so I know it's clean, it was leaking, third time, not fun.
I have noticed that the valve train / lifters are noise but have always been that way. Engine and trans are the only two pieces of drivetrain with 178k, all others have been gone through, regear and she installs.
I have read your beater thead, Ehall, and it made me think of the trans being a heat concern
 
You already verified the efan turns on when its supposed to but have you checked the actual engine temperature with an infrared temperature gun to verify the actual engine temperature is what the cluster temperature gauge indicates?
If lucky, maybe a bad temperature sensor.

Another remote possibility is the exhaust could be plugged or partially plugged (maybe the CAT) but that would likely throw CELs.
 
The guage inside is showing just over 210 when the fan come on, think 212 is factory turn on. With it being a 94 is the computer smart enough to show a cat issue
 
What type head bolts do you have? One time use, torque-to-yield bolts? Many years ago I chased an overheating problem with my 88XJ which did not have torque-to-yield head bolts. On hard acceleration, on a hot day, I saw a momentary puff of white smoke which then stopped when I let up on the throttle. The XJ pressure-tested fine. Obviously, a head bolt would stretch slightly, release coolant into a cylinder and then the gasket would reseal. It only happened on hot days and hard acceleration. I pulled the head and had it resurfaced and then installed a new head gasket with new head bolts and the problem was solved.

Best regards,

CJR
 
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