over heating issue.

91 xj.

whats been done to the rig already.
water pump is 10months old.
thermastat is 185 and is 10 months old.
thermastat housing is 10 months old
rad is 2 weeks old. (had to replace it due to car wreck)
16lb cap is 2 weeks old.
fan clutch is 2 weeks old
no hood mods yet. looking into it.

problem,
no matter what i do i cant keep temps under 230.
its fine if i drive it around in the morning when outside temps are cool or late at night when temps are cooler. but during the day if its above 90* truck will climb temp until it hits the second white line above 210.

(not my pic, but this is the point where i pull over and let it cool down for 20-30mins)


now what i have is a dual fan setup that came off an old race truck we have sitting at my shop.. its 26 inches wide and dual 12inch fans..
what i want to know is can i remove the ac/electric fan, as well as the mechanical fan and replace it with this? my plan is to wire it to
ignition hot so when i turn the key on they come on and when the key is off they turn off.

ive already done some measuring, it will fit and be a nice tight fit, but i will have to remove the ac fan as well as mechanical fan


im just not sure how it will effect the ac fan (that does not turn on when it hits 230* btw. i have to turn on the ac to get that fan to turn on.

will i be able to completly cool my truck with both of these fan instead of the electric fan/mechanical fan combo on it now?

How bad is your exhaust manifold leaking? I noticed my temps drop once I broke down and bought a new manifold.

xeroOTG said:

How bad is your exhaust manifold leaking? I noticed my temps drop once I broke down and bought a new manifold.

Click to expand...

good question it has a few cracks and should probably either be taken out and welded up or replaced.

Fix your exhaust leaks and make sure the seal between the downtube and collector flange is sealing. I had a leak there that was blowing hot air on the block causing the motor to run really hot. Once that was fixed my overheating problems went away.

One other thing to consider - your temp sender is at the back of the block and that sensor is something that can fail. On my 92 (or was it a 93?) I chased high temps to the point I replaced a new water pump with a hesco and installed a Taurus fan for it to be a failed sensor. The bwd sensor from the parts store is not quality. Get a Mopar. They can be haggled down to $20-30 with the right parts guy. I think the dealership I went to even had one on the shelf.

my temp sensor is fine. i tried like 4 from autozone before using the one that was on my old head when the head gasket let go. hence everything is 10 months old. guess ill start with a header and down pipe and move on from there. i still want to do the electric fan swap sooner or later.

#S194 said:

Fix your exhaust leaks and make sure the seal between the downtube and collector flange is sealing. I had a leak there that was blowing hot air on the block causing the motor to run really hot. Once that was fixed my overheating problems went away.

Click to expand...

Agree. Also, when was the last time your replaced your catalytic converter?

JeepityJeep said:

Agree. Also, when was the last time your replaced your catalytic converter?

Click to expand...

last November for smog.

smokinu said:

91 xj.

now what i have is a dual fan setup that came off an old race truck we have sitting at my shop.. its 26 inches wide and dual 12inch fans..
what i want to know is can i remove the ac/electric fan, as well as the mechanical fan and replace it with this? my plan is to wire it to
ignition hot so when i turn the key on they come on and when the key is off they turn off.

ive already done some measuring, it will fit and be a nice tight fit, but i will have to remove the ac fan as well as mechanical fan

im just not sure how it will effect the ac fan (that does not turn on when it hits 230* btw. i have to turn on the ac to get that fan to turn on.

will i be able to completly cool my truck with both of these fan instead of the electric fan/mechanical fan combo on it now?

Click to expand...

Is it just me or is the fan on the right missing two blades?

My two cents:

I'd consider connecting your current electric fan through a dash mounted toggle switch before going to all that trouble. A fan that runs constantly can be a bad thing when you don't need it.

Is yours a renix 4.0 or a HO 4.0? IIRC the changeover happened in 91.

If it's RENIX, you have three coolant temp sensors (if I'm remembering correctly the HO combines #1+2 into a single sensor):

1 - drivers side of block, near motor mount. This sensor communicates with the ECU and controls fuel mix
2 - rear of head next to valve cover, up against firewall. This sensor communicates only with the dash temp gauge.
3 - Electronic fan temp sensor. This connects into the radiator, and tells your e-fan when to kick on (about 215-220deg IIRC).

If #1 is bad the ECU might be dumping in an incorrect amount of fuel, causing it to run hot
If #2 is bad your dash gauge could possibly be showing a much higher reading than is correct
If #3 is bad the E-fan isn't turning on when the engine gets into higher temps, causing it to run even hotter.

Does your current E-fan run once the Jeep gets above 210ish?

fishinpolejoe said:

Is it just me or is the fan on the right missing two blades?

My two cents:

I'd consider connecting your current electric fan through a dash mounted toggle switch before going to all that trouble. A fan that runs constantly can be a bad thing when you don't need it.

Click to expand...

haha , yes its missing two blades. its been through a few roll overs on a race truck.

Royal Nonesuch said:

Is yours a renix 4.0 or a HO 4.0? IIRC the changeover happened in 91.

If it's RENIX, you have three coolant temp sensors (if I'm remembering correctly the HO combines #1+2 into a single sensor):

1 - drivers side of block, near motor mount. This sensor communicates with the ECU and controls fuel mix
2 - rear of head next to valve cover, up against firewall. This sensor communicates only with the dash temp gauge.
3 - Electronic fan temp sensor. This connects into the radiator, and tells your e-fan when to kick on (about 215-220deg IIRC).

If #1 is bad the ECU might be dumping in an incorrect amount of fuel, causing it to run hot
If #2 is bad your dash gauge could possibly be showing a much higher reading than is correct
If #3 is bad the E-fan isn't turning on when the engine gets into higher temps, causing it to run even hotter.

Does your current E-fan run once the Jeep gets above 210ish?

Click to expand...

guess i didnt post some of that info in here. its an HO. and i only have 2 sensors one at the back of the block on the head and the one on the thermstat housing...

im going to tie in a mechanical gauge tonight inline with that 2nd sensor to get another reading on temps. because i took my inferred gun and did some testing and when my gauge on dash was sitting at the 2nd white line. the head was about 212 degrees.

Definitely fix your exhaust leak. Since I had my head gasket and newer, non-cracked exhaust manifold, no overheating. Yes, it gets warm on hills and playing in the dunes but zero overheating.
Even before I fixed it, using an IR temp gun my temp gauge reads approx 12 degrees high.

Johnnie Walker said:

Definitely fix your exhaust leak. Since I had my head gasket and newer, non-cracked exhaust manifold, no overheating. Yes, it gets warm on hills and playing in the dunes but zero overheating.
Even before I fixed it, using an IR temp gun my temp gauge reads approx 12 degrees high.

Click to expand...

acording to my newly installed mechanical gauge. mine is about 20 degrees off.