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HELP!!! Fan Blades hitting engine damper/harmonic balancer

X

xzalt

NAXJA Forum User
Location
Knoxville, TN
I replaced my serp belt last night, started it up, worked great ran it for about 5 min. Today, started it up and it immediately threw the belt, and got caught in the engine damper, so I retensioned the belt and now the fan blades hit the engine damper/harmonic balancer by a centimeter or so. I need some immediate help. What can I do? what did I do?

gavin
 
Last edited:
First why did you replace the belt ? was it shredding ? The harmonic dampners have a tendency to fail and will move either in or out which will pop a belt.
If it was not routed right that might do it too. Hopefully the belt did not bend the fan otherwise you will need a new one. Look at the dampner and see if it has started walking in or out and go from there.
How did you set the tension ? I use a NAPA KrikitII belt tension gauge, $15 or so at napa. New belt tension should be 180lbs, used belt [run more then 15 minutes] should be set at 170lbs according to my 98 FSM.
When I do a belt I also do my idler pulleys at the same time, everytime on all three of our jeeps.
 
xzalt said:
I replaced my serp belt last night, started it up, worked great ran it for about 5 min. Today, started it up and it immediately threw the belt, and got caught in the engine damper, so I retensioned the belt and now the fan blades hit the engine damper/harmonic balancer by a centimeter or so. I need some immediate help. What can I do? what did I do?

gavin
Click to expand...

Harmonic damper is probably coming apart unless you did something really bonehead to the fan/clutch/WP pulley. Inspect the HB carefully.
 
here are some pics of it currently

dsc00171.jpg


dsc00170.jpg


dsc00169.jpg


I replaced the belt because of some high pitched noises and it was recommended to me that the belt was the problem.

Belt tension was just guessed at, I called around auto stores trying to find a tension gauge, but no one had ever heard of one, so I figured no one used them. bad assumption.

so are we confirming that it is the HB, I don't know what is should look like normally, much less now?

thanks
 
xzalt said:
I replaced my serp belt last night, started it up, worked great ran it for about 5 min. Today, started it up and it immediately threw the belt, and got caught in the engine damper, so I retensioned the belt and now the fan blades hit the engine damper/harmonic balancer by a centimeter or so. I need some immediate help. What can I do? what did I do?

gavin
Click to expand...

As the others said, check the harmonic damper. I'd be surprised if it's still intact because from what you've described, I'd bet the farm that the outer part of the damper has moved forwards so it's thrown off the belt and it's being hit by the fan.
 
Now that I've just seen the pic, it looks like I've won my bet.
Replace the damper, install a new belt (again) making sure that it has no more than 1/2" of deflection along its longest free length (usually idler pulley to PS pump), and you'll be good to go. It might be a good idea to replace the idler pulley as well as Rich P suggested. Just make sure that you don't overtighten the bolt when you install the new one.
After about a week, check the belt tension again. The belt can stretch when it's new so you may need to retighten it.
 
xzalt said:
would this problem have been caused by the new belt? or a current problem just exacerbated by the new belt?
Click to expand...

Neither.
The outer part of the damper walked forwards and threw off the old belt. You didn't spot that before you installed the new belt so it happened again. Now you know what the problem is and how to fix it.
 
Yep, that's coming apart. 1/2" deflection is good as well as a gauge. Another method I use is to tighten is just to the point where I can hear a little squeal with the A/C compressor running when I goose the throttle. Very easy to overtighten with that power steering pump adjustment scheme.
 
thanks for all the quick replies.

I've been reading around and to replace the HB I'll need a puller from AutoZone, and a new HB.

I've also read I should replace the front seal?

Any other things I should do while there, or tricks? I'd really prefer to not remove the radiator. B/c I assume that will add an hour or so to my work. plus its something I've never done before.

on the idler pulley, I spun it and it spun freely. There is only the one correct?
 
I've been reading about the trick to loosen the bolt, with the breaker bar and the starter, which side does the breaker bar rest on?

also, with the re install. there is a kit? or you can use washers and a longer bolt? I don't quite understand that one.

One last question, how tight should the bolt be on replacement?

thanks
 
xzalt said:
I've been reading about the trick to loosen the bolt, with the breaker bar and the starter, which side does the breaker bar rest on?

also, with the re install. there is a kit? or you can use washers and a longer bolt? I don't quite understand that one.

One last question, how tight should the bolt be on replacement?

thanks
Click to expand...

Yeah, look at the pulley bolt and determine the direction of engine rotation. Then figure-out how to place a long breaker bar w/socket on the bol and rest that on the ground or something very solid under the chassis. Once you're sure it's right, bump the starter and it should break loose. Disconnect coil if you do this with the ignition switch. Otherwise, try making a clip-on starter button and attach that to the solenoid control terminal/path. That way you can bump the starter while watching what's going-on.

To pull the pulley hub find bolts that thread into the pulley web and then drill a piece of angle iron so that can be loosely bolted to those holes on top of the crank bolt backed-out a few turns. Tighten the smaller outer bolts and that will pull the hub from the crankshaft.

I didn't change the oil seal and haven't had any problems for nearly 7 years when I did this to my '89.
 
Same thing happened to me about a month ago on my 98.
 
xzalt said:
with the reinstall, how does it work with the bolt and washers?
Click to expand...

Going on is much easier because the bolt can draw the hub onto the crankshaft. But, to insure an easy-go of that, heat the new HB in an oven to between 120-150 degrees just before installation. Don't melt the rubber but I'll bet a six-pack it will slip right on with a gloved hand if you do that.

Use a drop of Loc-tite and I remember holding the pulley with a large screwdriver/pry bar wedged in-between those small bolts in the pulley hub while torquing the crank bolt. Oh yeah, coat the seal surface with engine oil too and be gentle with that while installing.
 
XJXJ said:
Going on is much easier because the bolt can draw the hub onto the crankshaft. But, to insure an easy-go of that, heat the new HB in an oven to between 120-150 degrees just before installation. Don't melt the rubber but I'll bet a six-pack it will slip right on with a gloved hand if you do that.

Use a drop of Loc-tite and I remember holding the pulley with a large screwdriver/pry bar wedged in-between those small bolts in the pulley hub while torquing the crank bolt. Oh yeah, coat the seal surface with engine oil too and be gentle with that while installing.
Click to expand...
You should NOT need to heat the balancer up to get it on the nose of the crankshaft, PROVIDED the surface of the nose of the crank is CLEAN, and RUST FREE.

If it's NOT, clean it with a "scotch-brite" pad. Apply some motor oil prior to sliding the balancer on.
 
AZ Jeff said:
You should NOT need to heat the balancer up to get it on the nose of the crankshaft, PROVIDED the surface of the nose of the crank is CLEAN, and RUST FREE.

If it's NOT, clean it with a "scotch-brite" pad. Apply some motor oil prior to sliding the balancer on.
Click to expand...

LOL... I never said you MUST heat the pulley only that it's a helluva lot easier to "slide-it-on" if you do. About 10 minutes in the AZ sun should do the trick too! Clean is the only way to do anything and I would assume others should already know that or they have no business messing with wrenches.
 
XJXJ said:
Clean is the only way to do anything and I would assume others should already know that or they have no business messing with wrenches.
Click to expand...
Having read many posts here over the years, I don't assume ANYTHING about the population of owners here, and their wrenching abilities. :dunno:
 
thanks a lot for all the help and tricks and responses. She is up and running once again.

I do have one other question since the immediate issue is fixed. I want to understand why.

why didn't this happen before I replaced the belt? just because the old belt was more flexible?

thanks
 
This is, unfortunately, a natural consequence of the constructio of a production damper. The elastomer eventually begins to get a little soft, and it doesn't hold the parts together anymore. Then, the outer ring starts to "walk" - just like you're seeing here.

Problem is, there's no way to predict when this is going to happen!

Fluidampr has solved this nicely with their construction - the damping member is fully enclosed and "floats" in a silicone fluid. The hub is extended to create a "sleeve" for the ring to be sealed into, so it's not going to walk.

I wish they'd make one for the 242/258 - even with the extra cost of the unit, I'm sure it would sell well. It does a better job than the production unit (I've used a few on SBChevvy/BBChevvy and MOPAR) and is as reliable as the average rock - it just don't break. We need to let them know we're interested - and it would be easy for them, since the AMC I6 is internally balanced.

Let me just say that if they started production, I'd take four of them right now - more when I get some more XJ/MJ's going...

5-90
 
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