aaronvincent

I've been having some trouble posting on here but I figured I'll try again to see if it works, so here it goes. I have a 1996 Jeep Cherokee with the HO (not Renix) 4.0L 6 cylinder and the automatic transmission with the CommandTrac 4x4 system and it runs insanely well for its age. However my electric cooling fan is not coming on when the vehicle reaches 218F at idle which causes it to overheat unless I keep it moving which is a pain where I live. I put all new coolant in it, replaced all the under-hood relays and also replaced the coolant temp sensor (located on the thermostat housing) but still the electric cooling fan does not come on. I found out if you remove the fan and apply 12V directly to it, the fan itself does work. I also found out if you unplug the temp sensor while the jeep is running the cooling fan is then prompted on (and so is the CEL). After more digging I found out that if you unplug the temp sensor with the jeep off and then plug it back in AND THEN start the jeep up the cooling fan will also come on but once you turn the jeep off and start it again the same problem occurs...no cooling fan. After much research I was told the fan control module is usually the culprit but it seems this era of Cherokee does not have one and if it does it's often built directly into the fan assembly itself? I'm no stranger to car repair but this one has me stumped. I really don't want to rig up a dashboard cooling fan toggle switch like so many previous sh*tboxes I've owned, I like to keep things oem but my last option is to buy a new fan assembly. So before I throw more monies into it I'd like to ask the opinion of those who probably know more about this than I do. Any thoughts?

PatHenry

You shouldn't be reaching 218 at idle. Spec is 210, typical is like 200-205. I generally find that my 95 runs lower than average. Double check the exact temp for a 96. It did vary somewhere in that range (218-223) between certain years.

If your fan turns on when the plug is pulled off the CTS AND directly when jumped to the battery, then the problem is between the CTS and the computer. Did you check and clean the connectors and check the wiring?

Was the new CTS Mopar?? The XJ seems to be particularly sensitive to aftermarket sensors - I might try a Mopar CTS if it's not since it's likely cheaper than a new or refurbished computer. I say this as someone that's been swapping out trouble free sensors with new Mopar parts just out of fear of not being able to find a Mopar replacement in the near future.

jordan96xj

I have a 96. I also have a digital dashboard that shows me exactly what the computer thinks the engine coolant temperature is (which it derives from the voltage resistance produced by the engine coolant temperature sensor at the thermostat housing).

The fan comes on at 220f (to be more accurate let's say always comes on in the range of 219-221F) I listen for it, and it has never failed to come on when those temperatures are reached. I also have a visual alarm activate at 219F on the digital dashboard, so that I am reminded to listen for the fan.

I can manually control the fan by activating the air conditioning. On a 96 if the AC compressor is active, so is the electric fan. I don't know if you have AC. But it does provide some manual flexibility for controlling the fan, and I occasionally take advantage of this when I'm idling for extended periods or climbing major hills.

For coolant temps that creep up when sitting at idle, to the point where the fan kicks on and knocks the temp back down to the 210-213 range (then process repeats) this typically indicates the need to replace the viscous flan clutch. (cheap and relatively easy).

My typical operating temperature these days is around 203-205. I currently have a Mopar 195F thermostat installed. When I bought the XJ it also had a Mopar 195 in it and the operating temperature was typically 210F (what most people consider normal).

aaronvincent

Thank you for the replies! The new CTS was from O'Reileys unfortunately so I will have to use my ohm meter to determine if it's getting accurate readings. The one that came out of the Cherokee didn't look too bad honestly but it was replaced due to the inop cooling fan. When I say the cooling fan doesn't kick on at 218F like it should I mean that I'm reading the temp gauge on the dashboard and it sits directly in the middle for a little bit but once I sit for like 10 minutes...there it goes slowly into the red. Very slowly but still it goes there and I've never actually let it get into the red for fear of damaging the engine so I shut it off right before it gets to the red mark, but still no cooling fan ever came on in that entire sweep of the needle. I did check the wiring for breaks and found none so used some QD Electronics cleaner and sprayed it into the connector for the CTS and the connector for the cooling fan, no change. My Cherokee has the whole AC system complete still but it has no freon in the system so it doesn't turn on (or turn the cooling fan on for that matter).

I decided to order a new cooling fan assembly anyway because this one was rubbing on the PS pulley due to the previous owner changing the radiator and not mounting the little tabs back correctly and it has some deep scuffs on the fan blades that I don't like. Based on what I've read here perhaps I'll change the thermostat out and inspect the viscous fan clutch while I'm in there putting in the new fan. Is there anyway to determine if the fan clutch needs to be changed besides a visual inspection? The computer will be my very last resort if I still can't figure it out, I absolutely hate dealing with computers on cars but I know how Chrysler products can be with their computers, just ask Scotty Kilmer lol. On a related note regarding the thermostat the Cherokee does take quite awhile to warm up (get to the middle of the gauge), maybe like 10 minutes, does that seem like it may need a new thermostat?

Sorry for all the questions I just love my Cherokee quite a bit and I want it to be as close to perfectly operating as possible, thanks!

aaronvincent

Having a heck of a time posting, keeps saying "a moderator needs to approve" but no moderator ever shows up so idk on that but anyway thanks for the replies! I did indeed check/clean both the CTS and cooling fan connectors with QD Electronics cleaner and that made no change. Checked/traced the wires for damage but found nothing. The CTS is from O'Reileys so that isn't great within itself, I checked it with my ohm meter set to 20k and it appears to be working, it gradually dropped in ohms as the car heated up. Only replaced it due to inop cooling fan. When idling for long periods and the temp needle is just about to touch the red most times still no cooling fan comes on so I just shut it off or keep moving to avoid overheat conditions (especially here where it's 100F + regularly). I checked the fan clutch with a rolled newspaper while the Jeep was running, ate right through it with no issue whatsoever. Tested it with the vehicle off too and there's plenty of resistance when trying to spin by hand in either direction so I believe it's working correctly. Unfortunately in my Cherokee the AC does not work, it is complete but needs to be recharged so that doesn't prompt the cooling fan on anymore. So after reading the replies I've decided to order a new OEM Mopar 195F thermostat because I don't know the history of the thermostat and I already ordered a new cooling fan because this one has a few deep gouges in it from where the previous owner didn't put it back in correctly and it touched the PS pulley...not a mechanically inclined guy he was. Now regarding the computer that is the very last resort for me because I hate fiddling with those sensitive little computers, especially Chrysler computers that are known to be junky so I will leave that for last due to price/annoyance factors.

Thus far my plan of action is to put the new cooling fan assembly in and see what happens. If nothing changes then I'll change out the unknown thermostat for the OEM one and flush the coolant again and then continue to monitor the temp. If it still acts up I will look into a new OEM CTS, I do not believe the fan clutch to be bad as it doesn't freespin even a little. I appreciate all the replies so quickly

PatHenry

A new e-fan won't help if it's not getting powered on correctly. Since you jumped it and it kicked on, you know it WOULD run if it got juice.

The t-stat may help with the overheating. When you go to do it, run a garden hose through the cold engine block (disconnect hoses, run water from tstat down and from bottom up.


Your e-fan problem is definitely CTS->PCM area - fan should kick on at roughly 220 which is well below the "near red zone". If the testing of the CTS shows proper output, the PCM may be faulty - see if you can find a junkyard one and swap it.. maybe they'll let you try it in their parking lot before buying..

The bigger issue is the high temp. I'd flush your radiator when you do the t-stat. Something ain't right.. maybe deteriorated water pump not flowing well..

aaronvincent

For absolutely sure I'll flush the engine block when I do the thermostat because when I got the jeep it had WATER in it that was a murky brown instead of actual coolant (since the owner refused to replace the obliterated coolant tank) which I did. I've already scoured the local junkyards for Cherokees but literally no one has even one around here, they command a premium and as such aren't often junked. So if I do get a PCM computer I'll have to go online, I don't have to program the darned thing right? It's old enough to be plug n play?

That deteriorated water pump you mention sticks in my mind a little bit, the reason being I hear a good bit of growling from the water pump area but the pulley doesn't wobble at all so I left it alone, super easy to change on these engines though (not like my V6 Sienna). After reading through pages and pages of info related to the cooling system of these cherokees I spent the last few hours looking up parts here and there and decided to do it up right instead of just flush the cooling system. What did I buy? Well I bought a new 3 row all aluminum radiator along with a brand new Gates water pump and the OEM Mopar 195F thermostat, just so I can make absolute sure this thing cools as good as it possibly can. I decided against the 1 row plastic fantastic radiator because that's what is already in there and obviously it ain't doing the job so out it goes. This thing has a special place in my heart for sentimental reasons so to me it's worth it, and in all honesty it didn't even cost a fraction of what it would to have a shop do all this so here's to the box on wheels I will report back after I do all of these repairs/modifications with the end result

jordan96xj

The cooling fan has a relay in the PDC. Before jumping to the PCM (computer). The relay (and the wiring to it) has to be ruled out. The power should also be jumped at the relay to test that the fan will come on when the relay is manually jumped (using a paperclip between the two large sockets).

PatHenry

Definitely check the relay in the fuse box under the hood.

I'd start with the radiator/water pump stuff first. The fan not cycling at 220 shouldn't even be a factor in overheating unless you're crawling or towing.
The standard radiator is generally sufficient, even the Autozone specials have generally good results - but for sure, if you're in hot weather and want to go with a higher end 3 row - nothing wrong with that.

I'd wager you have a water pump issue or even more likely the radiator is partially clogged considering the neglect you're reporting.

You can't trust that a pump is good by lack of wobble. The problem with old pumps is that they deteriorate and bits of the impeller get in the coolant and plug the passages.
I once had a fairly new water pump (00 TJ, but exact same part used on XJs) where the plastic impeller (OEM was metal, AZ special was plastic) sheared clean off - so no bearing noise, no wobble, no weeping, but also, no pumping of coolant. The Jeep couldn't run for more than a few minutes before nearing the red zone. Fun story.. 100's of miles from home, replacing a water pump in 90+ southern sun on the side of a highway.

PatHenry

If you do need to do a PCM, I believe it's plug and play up until the chip keys (00-01 years).

Key thing is to match the part number.

aaronvincent

I replaced all the relays in the PDC with brand new TE relays but I didn't jumper the two pins to manually command it on so I'll definitely give that a try after work tomorrow, that is a much appreciated tip! I did notice while replacing the relays that the one for the "AUX FAN" was a different brand than all the rest leading me to believe it was replaced before. I'd ask the previous owner about all this goofery but he's a few more feet below the ground than I am

Looks like I've got a good bit of detective work and or repairs to get to, but to me that's the fun stuff lol. As a side note the owner's manual is incredibly unhelpful when it comes to labeling what everything in the PDC actually goes to, very odd

aaronvincent

Okey dokey I "borrowed" a paperclip from work and bent it into a U shape then stuffed it into the two large terminals where the AUX FAN relay usually sits...and immediately the cooling fan came on full force like a hurricane so that area appears to be working correctly. So that's good at least. Upon crawling under the Jeep for something else I also noticed my transmission cooler lines are leaking pretty good so now I gotta go order those...off I go

aaronvincent

All the new parts have arrived! It's like a coolant based christmas. There's a new 3 row all aluminum radiator, new upper and lower radiator hoses, new water pump, new coolant and a new OEM thermostat. Now I just have to wait until my next full day off and it's a go!

Trying to resize these images but not having much luck with that, just go ahead and ignore my hideous 90's armchair lol

PatHenry

Some poor fools would call our XJ's hideous 90's (or 80's) suvs. Their loss of course.

aaronvincent

The Cherokee is beautiful to me, I love how angular it is.

After work I parked it on the side of the house and got to it. I had to remove quite a bit more than I expected to get the radiator out but eventually it came free, appears to be in good shape but who knows how old it is so out with the old 1 row and in with the 3 row! Hoses were old and mushy so those got changed (both upper and lower). The new cooling fan came finally so that went in too, no longer all gouged. Now the best part, the thermostat. Not only was it dead (I tested it by boiling it) but it was also a 160F and had no bleed hole at the top? I put an OEM Mopar thermostat back in that read 195F so that'll do a bit of good. Flushed the block for about 8 minutes with a garden hose stuffed in both upper and lower coolant passages until only clear flowed out. The absolute worst part was aligning the new 3 row all aluminum radiator because it's a good bit bigger and requires A LOT of fiddling/re positioning to install, had to remove the grill just to properly see where the bottom pegs sit. It also has a new coolant bottle (as the previous owner had a rag stuffed in it for a cap and it was BROWN. I'm out of sunlight now so tomorrow I will get to put the actual coolant mixture in (70/30 is how I usually go). Then I can spend forever burping the system of air yaay, overall not a bad experience. It's actually easier to do a water pump on this than my old 93 Corolla 1.8L, maybe even easier than my old Geo Metro 1.0L lol

also some cat fell asleep next to the old water pump while I was working, not my cat haha