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Long battle with overheating 96 XJ.

H

heisenberg

NAXJA Forum User
Location
Colorado Springs, CO
If you start it up and don't drive it, it will idle indefinetely at 200-210 and will never be a problem.

However, if you drive it for say 15 minutes it likes to get hot, and the longer you drive, and the more stops you come to it likes to get reallyy hot. This can be combated by blasting the heater, and it will level out at 210.

The strangest thing is the Jeep drives great, and I have no other problems with it.

I AM AT MY WITTS END
furious.gif


I will replace the head gasket if that's the problem, but I am scared it won't even help since there's nothing telling me that the head gasket is the problem.

Replaced so far:
Water Pump - (yes reverse rotation)
Thermostat (x2) - 195 Degrees with bleed hole (Working)
Burped system
Brand New Fan Clutch (Verified Working)
New CSF 2 Row Radiator
Checked for combustion gasses in radiator with block tester (x3 all negative)
Pressure Tested System (x2 and nothing odd showed up)
No coolant in oil, oil in coolant, white smoke in exhaust, or drops of water
NO SIGNS OF HEAD GASKET LEAK
Ensured serpentine belt is tight
Replaced Catalytic Converter
Fresh 50/50 coolant with distilled water
AC Condensor checked, and cleaned with compressed air
Verified temperatures with an IR Temperature Gun
Verified electric fan is working
Verified heater core is not clogged
Verified block coolant jackets arent blocked

Only odd thing is after driving for a while top radiator hose gets EXTREMELY HOT AND EXTREMELY HARD, not sure if this is normal

ANYONE out there who battled/is battling something similar, or can offer professional advice I would really really really appreciate
 
the hard hose is not normal, have you replaced the bottom hose? it could be collapsing under high RPM due to suction from the water pump. there should be a spring inside it to keep this from happening but new hoses sometimes do not come with the spring.

that's my bet, especially since you said the top hose gets hard and it idles fine.
 
What Radiator cap you using? The upper hose shouldn't get EXTREMELY hard. There should be never be more than 16 psi in the cooling system. What lower hose you running? Good quality one with a spring is it. Could be colapsing under high RPMs

Dumb question here.. But is the Thermostat in the correct way? (not evern sure that possible) What happens if you try and run it without one?


Damn you guys are quick..
 
GrimmJeeper said:
the hard hose is not normal, have you replaced the bottom hose? it could be collapsing under high RPM due to suction from the water pump. there should be a spring inside it to keep this from happening but new hoses sometimes do not come with the spring.

that's my bet, especially since you said the top hose gets hard and it idles fine.
Click to expand...

The bottom hose has a very hard spring in it, and is in good condition.
 
CaliXJ said:
What Radiator cap you using? The upper hose shouldn't get EXTREMELY hard. There should be never be more than 16 psi in the cooling system. What lower hose you running? Good quality one with a spring is it. Could be colapsing under high RPMs

Dumb question here.. But is the Thermostat in the correct way? (not evern sure that possible) What happens if you try and run it without one?


Damn you guys are quick..
Click to expand...

Stant Rad Cap, and the thermostat is in correctly lol.
 
Sounds like the block is clogged to me
 
Does it have an auto trans by any chance? If so, get a GOOD transmission cooler and install it. My 91 had problems like this and a trans cooler helped a LOT. Like 20° + help
 
One thing most people never consider is an exhaust leak blowing on the block from the donut flange area or the manifold gasket.

Hard is a relative term. Have you tested the cap with a pressure tester. Is it an OEM pump or a special pump?

I recently discovered that the radiator inlet sides run at higher pressures (pump outlet side) than the radiator outlet sides due to the pump pushing on one side and sucking on the other, then add in the pressure drop across the radiator core....), and the cap is on the outlet side!!

Renix Jeeps have the cap on the other side, and a coolant-bottle bypass on the pump outlet side that feeds the pump inlet side, and an air cushion in the bottle, so under normal circumstances they operate at about 9 psi and 200 F (I measured it on mine !!!!!).

The HO rigs go straight to 16 lbs on the low pressure low temperature sides, and vent to the OPEN bottle until they reach peak temperature and stabilize.

What is the peak temperature at the T-Stat housing reading?

Have you done a ohms resistance test on the temp sensor in the T-Stat housing (power off) to see if it agrees with OEM spec versus actual temperature? What temp is the E-Fan coming on at?
 
Last edited:
Ecomike said:
One thing most people never consider is an exhaust leak blowing on the block from the donut flange area or the manifold gasket.

Hard is a relative term. Have you tested the cap with a pressure tester. Is it an OEM pump or a special pump?

I recently discovered that the radiator inlet sides run at higher pressures (pump outlet side) than the radiator outlet sides due to the pump pushing on one side and sucking on the other, then add in the pressure drop across the radiator core....), and the cap is on the outlet side!!

Renix Jeeps have the cap on the other side, and a coolant-bottle bypass on the pump outlet side that feeds the pump inlet side, and an air cushion in the bottle, so under normal circumstances they operate at about 9 psi and 200 F (I measured it on mine !!!!!).

The HO rigs go straight to 16 lbs on the low pressure low temperature sides, and vent to the OPEN bottle until they reach peak temperature and stabilize.

What is the peak temperature at the T-Stat housing reading?

Have you done a ohms resistance test on the temp sensor in the T-Stat housing (power off) to see if it agrees with OEM spec versus actual temperature? What temp is the E-Fan coming on at?
Click to expand...

Not an OEM water pump, but the one I replaced was in perfect condition, only replaced it because i had the suspicion it might be the wrong rotation. Both pumps yield the same problems.

Peak temp of thermostat housing is always what the gauge reads + (5-10)

Have not done an ohms resistance test, not that handy electrically

E-Fan comes on at 218 or so

It does have an exhaust-manifold leak, are you saying this could be causing my problems?

How hard should the rad hose be getting when its at 210? I can still squeeze but only barely.
 
E-Fan should be coming on at about 208 I think, but I am not an HO expert on the temp set point for 96. Check with others here, or search older threads for the exact temp. If I am right the Temp sensor may be off, and waiting to long, too hot to turn the fan on and off, letting it run too hot. Many of us have wired in a bypass, manual override switch to the E-fans

What is the highest T-Stat temp you are seeing?

Yes, the exhaust leak can be all of your problem if it is blowing on the block or intake manifold or both!!!
 
aquino#s194 said:
Take my word for it...Ecomike is right about the exhaust leak causing you to overheat. Thanks to him I solved my overheating problem.
Click to expand...

Well I guess my exhaust manifold is getting a good welding. Ill let you know the outcome. Thanks!!


to the guy that found out his problems were caused by this can you tellme the symptoms you experienced as far as overheating?
 
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