Fan Clutch Question(s)

Hello all,

I own a 96 XJ, straight six, selec-trac, and all OEM equipment (bought the Jeep new).

Several weeks ago I noticed that the engine temp gauge was spiking up. Needle normally reaches dead center ("210") and holds there. Instead, it was now creeping upwards during idling at stoplights after the vehicle had been run a while (15-20 minutes/5-10 miles.

Shortly thereafter I noticed a "grumbling" sound coming from the engine compartment. Again this would happen once the vehicle had been run for a few minutes/miles. It was limited to slow acceleration from either dead stops, or slow forward/reverse movement.

Thinking that the two were related (and that the higher temps being registered were causing damage to the engine) I took the Jeep into my local mechanic this past weekend. His diagnosis: fan clutch was messed and needed to be replaced. Which I had him do.

Picked up the Jeep yesterday and it's still having problems . Instead of a "grumble" during acceleration from dead stops it's now making this loud "fluttering" sound during acceleration at higher speeds (starting at about 25 mph and working up to about 45mph.) The closest thing I can compare it to is the sound made by taping a baseball card to a bike frame so it sticks through the wheel spokes and makes noise when the bike is ridden. The "flutter" is sensitive to both speed and the amount of pressure I'm putting on the gas pedal ... by changing the speed/acceleration/pressure on the pedal I can control both the amount/duration of the flutter and the loudness.

I've also noticed that this noise only occurs when the vehicle is in gear and moving. If I put it into neutral/park and vary the pressure on the gas pedal everything sounds just fine throughout.

Additionally, the engine temp gauge is behaving differently now. Where it used to spike up (during idling, usually) and remain steady, the needle now spikes up (again, during idling), but then drops down to it's "usual" ("210") position. In fact, I've noticed that when I turn the engine off and then move the key forward to the "on" position without restarting the needle spikes up MUCH higher than it ever is when the engine is running.

So, having said all of this (I've tried to be as detailed and specific as possible, sorry if it dragged on a bit), does anyone have any suggestions for this decidedly "non-gearhead" Jeep-owner about what the problem might be (is it really the fan clutch, could it be a botched fan clutch installation, etc), how serious it is (is it dangerous for me to drive my Jeep any further than to get it back to the mechanic) and any suggestions of other things that I might tell the mechanic to look at/for in attempting to resolve this?

Thanks for any help and suggestions!

--Garth

First thing I would look at is the clearance between the fan and the radiator, most aftermarket fan clutches are a shade too long and it might be hitting something, poke around, make sure your mechanic didn't miss tightening anything down that might be shifting and hitting the fan or something else, watch your fingers though if you do it while it is running and if you wear a tie keep it on the front seat or in the office.
When the jeep is cold that mechanical fan makes a roaring sound then it frees up till it gets hot.
Temp getting higher as shutdown is normal, the head gets the hottest, it's from residual heat build up, the gauge sender is in the front of the head where the thermostat is, it's where the top hose goes from the radiator to the engine
Rule of thumb is that the OEM jeep supplied fan clutch is the best way to go.

Agreed. The initial diagnosis appears to have been correct, based on the symptoms you described and the age/mileage of the vehicle.

It sounds like you had this work done by an independent shop, not a dealer. It has been pretty well established that many of the after-market replacement fan clutches, although listed for the XJ, are in fact slightly longer (deeper?) than the OEM and may come in contact with the radiator.

Take a look at the engine side of your radiator and see if it looks like the fan clutch has been rubbing against the cooling fins. If so, take it back and tell the guy to replace it again, with a dealer unit that fits correctly.

Check the fan shroud and where the rad overflow tube is. Mine did this once when the overflow tube wedged between the shroud and radiator. The fan blades would hit the displaced shroud at certain throttle positions as the motor moved on the engine mounts.
Oh, and check your motor mounts also.

Bones :skull1:
#6

Thanks for the replies!

I believe that the new fan clutch is OEM. I had to wait through the weekend and Monday as the two the mechanic orginally ordered from his distributor didn't fit (they were off by about an inch he said).

I checked the engine and sure enough the fan shroud (right along the rear edge) is chewed up a bit from being struck by the blades, even though there appears to be a decent gap between the two. The shroud also appeard to be loose/unsecured on the side where the striking is occuring. My take on this is that when the Jeep is turned off at night, the shroud stiffens as it cools. Once I start up and get rolling in the morning the shroud heats up and becomes more pliable. This allows the airflow to push the shroud back into the blades, especially during acceleration ... which is why I'm only hearing the noise after I've been moving for a few miles. This sound reasonable?

Another question that I now have on the matter: Since the fan clutch was replaced I'm seeing the engine temp gauge behave differently. For the first seven years of my Jeep's life the needle would rise from the left and then stay rock solid pointing straight up (at "210") When the clutch started to go bad (I think) the needle would spike up during idling and then hold position a bit below the red zone. Now that the fan clutch has been replaced, the needle is back to "normal" as long as the Jeep is in motion ... but it still spikes up during idling. Now, however, it drops back to "normal" when I resume forward motion. Is this something to continue being concerned about (I've read the other posts about how XJ engine temp gauges aren't necessarily accurate ... but I don't know if that covers the kind of dancing needle that I have) and what might the issue be.

Thanks again!

--Garth

Your '96 is now approximately 7 or 8 years old. The radiator has fairly small tubes and over time they get plugged up with corrosion. A radiator shop should be able to check it for flow, and possibly flush it out. However, I think you should assume it is nearing the end of its useful life. The OEM radiator on my '88 sprung a leak in '99, but it had been overheating badly in very hot weather for a couple of years prior.

The radiator shops can also remove the tanks and "rod" out the cores, but on an old radiator it may not be worth the expense, because the corrosion weakens the joints and the tubes, and you may spring a leak right after paying to have it roto-rooted out. IMHO if a radiator shop confirms that it's not flowing what it should, if a reverse flush doesn't fix it then it's time to replace the radiator.