Viscous fan blades hitting crankshaft pulley

I repalced the belt about six weeks ago and retightened it just recently. Today coming to work I noticed noise and found that the belt had moved out a track and by spinning the fan that the blades are just barely hitting the crankshaft pulley. I put the belt back in place thinking that by being off it may have been tweaking the fan a bit, but it's still doing it.

It's still pretty dark out here and will be again when I get home. Anybody know what may be causing this? I'm thinking maybe just add washers/spacers to the viscous fan nuts.

maybe the water pump is going bad.. My neighbors went out the other day and it locked up the pump pulley and fan was sitting way off center...

just something to look for

HTH

Probably the bearings behind the fan pulley. Or maybe the studs backing out of the fan/pulley. On my 88, the studs have backed out and the nuts were still were I left them. The harmonic balancer, can separate and pull the belt off center, but this wouldn't account for the fan blades, hitting the crank pulley (or would it?).
I'd take a close look at the harmonic balancer/crank pulley and take the belt off and check all of the bearings, in the front.

i really hate having a mechanical fan there i wanna put an electric some day.

If the belt has jumped a notch, that is normally a sign that one of the pulleys is not sitting square. Make sure the bolts are tightened on the back of the PS pump and alternator.

Uh, crankshaft pulley? Is the harmonic balancer (yes, that IS the crankshaft pulley) failing? Has it walked out from the timing case cover? Stand by the airbox and sight along the belt. All of the pulleys should be in the same plane. I'll bet the crankshaft pulley isn't.

Thanks for the help everyone. Now that we have a little daylight outstide, I went out on my lunch break and was able to see what's up. The belt had started to jump out a slot again. I pulled the belt and checked all the pulleys and all were tight, but the crank pulley looked to be sliding forward a bit...there was a bit of shiny/clean metal showing behind it. I put the belt back on and then looked down over the pulleys...the crank puley looked out a bit. I was limited with tools so tightened it all back up and tweaked the fan blades a little in hopes to get home (10 miles) and work on it right tonight. Started it up to test it and got an aweful noise! Looked in and the crank puley has come way forward...the fan is totally blocked now. Better to happen now than at highway speed.

Anyway, I've got a buddy who lives in town going to bring me a couple wrenches to tighten it down and will add some locktite when I get home.

Questions:

What size bolt is it that holds the crank pulley on?

Why would this happen?

Do you fIgure it caused any damage? I think just the belt slipped...maybe the fan clutch got a little shock.

Without a tool how do you guess at correct belt tension? I hear it's 1/4" or 90deg deflection but what's that? Like with the ruler and measure the possible movement from rest halfway between the idler and ps pump?

Thanks again...HTH anybody else out there.

Are you sure that the whole pulley assembly (aka harmonic balancer) is walking off the front, or is it separating? This is not an uncommon failure.

Sounds like the harmonic balancer might be failing; there's a rubber piece sandwiched between the inner and outer halves of the HB, and most of the time when it fails you will see rubber sticking out the front of back of the HB. The inner and outer halves will move forward or back; sounds like your outer is moving forward but that's cheaper than the alternative where the outer eats your timing cover...

Jim

I'll know for sure if it's separating in an hour when I can pull the belt off again and looksee. If that is the case is there anyway I can get it back on and back home? Or am I going to have get a new one first? I've never played with this before but what I can see right now is the the outer piece walking forward and behind that another round piece starting to show (it's kinda shiny or cleaner in spots). I didn't notice any rubber. WHich is which and would I just replace the outer piece?

Thanks.

The harmonic balancer (crank pulley) is two rings, with a strip of rubber between them. The outer ring and the inner ring should be flush across the face. You can often see some irregularities in the rubber poking out.
A new harmonic balancers is cheaper than a new radiator. Eventually much of the moving parts in the front are gonna self destruct, when/if the fan blades are hitting solidly.
Sometimes the harmonic balancer comes off fairly easy, sometimes hard. I use a fairly heavy duty steering wheel puller. I take off the front bumper, when I do mine. It makes it easier, to be able to look through the slots behind the bumper and see what your doing, when hooking up the puller. Just my preference, the bumper doesn't really have to come off. I've had better luck, tightening up the puller then hitting the bolt/socket end of the puller (carefully) with a hammer. The jarring seems to get things moving easier than steady pressure. If you screw the hold down bolts for the puller in too far, you can damage the timing case cover, near the seal.

I just did this a couple months ago...

The bolts for the damper (removal, in the "arms" of the hub) are threaded 5/16"-18.

You will want a 1/2"-20 bolt, in steps from about an inch long to three inches long (or so) and some 1/2" washers to install the damper - hammering it in place is a great way to ensure premature failure.


You don't need to tear the front end to bits to get at the damper - just pull the hub bolt (3/4" socket, IIRC,) attach the puller, and remove the damper. It's a good idea to change the seal while you're about it.

After you've installed the new seal, apply a LIGHT film of grease to the seal lip and to the damper hub (inside and out,) align the keyway with the Woodruff key in the nose of the crankshaft, and press (BY HAND!) into place. Once you can't push it on any farther, select one of the 1/2" bolts you just got, put about three or four lightly greased washers on it, and turn it into the crank nose. Select a wrench, and turn it smoothly in until it bottoms.

Once you get down far enough (no, I don't know how far that is,) you can use the OEMR bolt and lightly grease the washer (BOTH sides!) so that it will act as a thrust bearing while you tighten the bolt. Once the damper is all the way down, torque the bolt to spec and take off running again.

I have found it useful, especially if you have more than one XJ/4.0 with high mileage, to keep a spare HD on the shelf - that way, you don't have to run for long with one failing.

5-90

When you get the bolt out that holds on the balancer take it on your parts run. Find/buy another one an inch to inch and a half longer. You will need it to be longer to start the new balancer - the old one is too short to reach the threads in the crank nose (at least in my '90.)
Once the new balancer is started on with the long bolt, you can swap it with the factory bolt and finish up. The long bolt was too long to torque down for me.
This sure was better than beating on it with a hammer that close to the radiator.

Not to steal 5-90's thunder . . . (beat me by a minute)

Pulled my HB a few months back with the standard HB puller you can buy at any decently stocked autoparts store...Canadian Tire should have one that will work. I think I got mine from Autozone (similar to crappy tire for us south of the border)

To re-install, I did exactly what 5-90 recommends, with the exception, I used a 1/2-20 all thread rod that I had in my shop, several large washers, and a 3 nuts. Two of the nuts I jammed together at the end of the allthread to serve as a "bolt head", and the 3rd one was what I used to tighten down on the stack of washers. I cut the rod down to 8 inches (if I remember right, it was a bit long...6 would have probably worked fine), and screwed the rod into the snout of the crankshaft as far as it would go by hand. Tighten up the nut/washer stack as others have described, and the HB walks right up on the crank snout. Once it was fully seated, put the normal crank bolt in and tighten up.

I also seem to remember when removing the crankshaft bolt, that I noticed the original HB was not fully flush on the snout of the crankshaft, but was proud of the face of the snout by a mm or two. (I'm not talking about the two pieces of the HB pulley being flush...those should be flush...I'm talking about the inner piece of the HB that attaches to the crankshaft itself.) The replacement HB I put on (also a factory unit) tightened up in the same way. Fully torqued, I removed the bolt, and checked for a gap and I had the same amount as the original. This was on a 98 XJ Sport. I dont know if this will be a valid observation on non OEM HB or other year 4.0's.

Dave

Great write ups guys, very helpful. I left the jeep here at work last night and had parts brought into to my local napa overnight. I plan on tackling this after work in the parking lot. I can deal with the dark but I hope it doesn't get too cold.

In hindsight I should have checked the thread from home last night...I don't have the varying sized bolts to get the new HB on. I just may have to do this over two nights.

FYI...HB and universal puller from NAPA came to $138 cdn (would you believe I just got a rebate check for almost exactly that earlier today!)

Thanks again.

BRRRRRR. Damn cold outside. All is going well...I think. I am just about ready to throw the new one on...will be doing that after work tomorrow night as I had to get the appropriate size bolts for the reassembly from home.

ANOTHER QUESTION: When I first went to loosen up the retaining bolt for the damper it spun the crankshaft about a half turn. I then got a helper to hold the damper while I broke it free and got the bolt out. DOES THIS SCREW UP anything? TIMING???

Timing shouldn't be affected. Cam is chain driven behind the timing case cover, distributor is driven by a gear down by the oil pump. It's pretty hard to either loosen or tighten the bolt without turning the crankshaft at least a little bit.

n5xl said:

To re-install, I did exactly what 5-90 recommends, with the exception, I used a 1/2-20 all thread rod that I had in my shop, several large washers, and a 3 nuts. Two of the nuts I jammed together at the end of the allthread to serve as a "bolt head", and the 3rd one was what I used to tighten down on the stack of washers.

Click to expand...

That's a valid idea, and something I've done myself sometimes (when I can find the bit of 1/2"-20 allthread I've got lying about...) but not everyone has access to that. So, I reduced it to something everyone can find (if you can't find 1/2"-20 bolts, you need to either find a better hardware store, or just plain MOVE!)

5-90

ChiXJeff said:

Timing shouldn't be affected. Cam is chain driven behind the timing case cover, distributor is driven by a gear down by the oil pump. It's pretty hard to either loosen or tighten the bolt without turning the crankshaft at least a little bit.

Click to expand...

Thanks...that's great to hear!