89 Comanche 4.0 screeching

[dunl]

Yes, screeching, not squealing....squealing doesn't hurt my ears from inside the truck.  Anyone have any suggestions?  Using a stethoscope to check the pulleys is only going to be a 100% chance of making me deaf.

One question...the fan.  How free does it spin usually?  That's my first thought. 

[Waytec]

I would check the idler pulley bearing. thy like to go without notice.

[dunl]

This would certainly be without notice.

[cLAY]

Best thing to do is pull the belt and spin each pulley by hand, alt and PS pump included.

The bearings for the idler pulleys are really cheap to buy at bearing place vs buying the assembly. Pretty easy to push in and out as well.

[dunl]

Thanks for the tips.  The fan doesn't seem to spin freely, and I think I will maybe dig into the belt removal tomorrow (pretty sure these ones don't have the "easy" spring tensioner, but rather the screw behind the power steering pump assembly.

Might be a good time to upgrade to two Taurus fans instead of the single engine powered fan.  Time to go research. 

[stroker sahara]

Is the truck auto or stick? My Manche had a squealing belt, or so I thought. I replaced the belt and all was quiet for a day and then came back. I then replaced the idler pulley. Then the PS pump, and then another belt, but it just seemed to get worse. Sometimes it would be quiet until I pressed the clutch, which made no sense. I had a hunch one day and had someone else press the clutch and I witnessed the crank pulley move ahead 1/4"-3/8". I next replaced the engine and the noise was gone. I hope you don't have the same issue as it was more work than I needed.

[The Machinist]

I had a hunch one day and had someone else press the clutch and I witnessed the crank pulley move ahead 1/4"-3/8".

That can't be good!  I've taken a few engines apart where there was so much crankshaft end play that the face of the crank counter weights were hitting the block.

[dunl]

Well, definately the fan.  The idler pulley spins freely, but the neither the fan or fan pulley doesn't.    I was planning to put in two stock electric fans (the MJ doesn't have one) but there is only room for one mechanical.  There isn't room for a second MJ electric fan to fit in where the mechanical one was (so I am told).

Suggestions?

[rws]

Buy a new fan cluth from Napa, aprox. $60  (??)  then go to PnP and get a 12 blade electrical fan from a newer XJ, it will drop right into your truck.   Replace your fan clutch and switch the plugs on the electric fan and your better than new.

Why the newer electrical fan??  Because it sucks the same juice as your old fan but has 10 or 12 blades compared to your original fan which has 6 which means far better cooling.  If you really want to get fancy, reconfigure your fan relay to a manual switch in the cab so you can turn the eletric fan on when you want to.

If you are doing this to fix a over-heating problem the only real solution is to convert the exsisting closed cooling system to an open system.

[cLAY]

Don't replace the stock mechanical fan with a stock XJ/MJ electric fan(6 or 12 blade). The XJ electrical fan is only meant as a booster and doesn't have near enough CFM to replace the mechanical fan.

If you want to go straight electric find a dual fan setup from a junkyard, try a grand Voyager with the 3.8L, it has a rad similar in shape to the XJ. I have one sitting here from when I had to swap motors on my '98 GV.

Also when I was looking for the Taurus fan for my ZJ I noticed that some Taurus came with a dual fan that looked to be close in size.

Make sure to upgrade the electrical system to support an electric fan, so far I have upgraded my alt and gone to dual batteries to support that stupid fan and just this weekend I blew out my Alt fuses(ZJs have two alt fuse in case you didn't know...) and have now upgraded my wiring to support my bigger alt.

Some XJ/MJs with the 5spd and no AC actually came with a single core rad. If you have over heating problems you may wish to get a new 2 core rad and that would be a good time to ditch the pressure bottle and get a rad with a filler neck.

[dunl]

No overheating problems guys.....unless "screeching" is caused by overheating?   

any special year on those Grand Voyagers?

[dunl]

Alternator bearings.  Looks like someone's bad soldering job on the back there now. 

Fan does not spin without drag, however, so I expect to replace that as well.

[cLAY]

The one I have here is from a '97 Grand Voyager but I think they are the same from '96-'99. I don't know for sure it would fit an MJ, just looks close when I eye ball it.

How tight was the belt? I took out my alt once after over-tightening the belt.

[dunl]

The one I have here is from a '97 Grand Voyager but I think they are the same from '96-'99. I don't know for sure it would fit an MJ, just looks close when I eye ball it.

How tight was the belt? I took out my alt once after over-tightening the belt.

Tight, but within the 1/2 movement.