86' Harmonic Balancer/ Rubber Isolated 3 groove pulley

[Massboy]

Have a question. As I've been doing my rebuild for the last two years, I used my original HB from my donor 86' motor. It is the expensive HB with the rubber that often deteriorates. Mine appears to be all intact yet I can turn the outer pulley each way until it contacts the inner hub. There are basically stops cast into each that prevent much movement either way but it can move.
There are two things I've noticed that I believe are related to this and I would suspect that I need to purchase a new one. First is at idle the truck is rather noisy with a "clacking" sound. If I unplug the alternator it goes away pretty much and even when plugged in, if I accelerate the motor it goes away and the truck gets very quiet. The second is when I shut the engine off there is a slight metallic sound as it stops. Of course most diesels stop abruptly do to the compression and I believe this metallic noise is again coming from the HB as the pulleys want to continue to rotate when the motor stops and the HB rotates until the stops contact each other.
I also believe the "clacking" is the HB under the load of the alternator, pwr steering pump, and water pump. I think the sound is generated because of a slight on/off during the strokes at idle VS. the load on the belts. I might be wrong but I would think I still need to change this HB. Like I said, the rubber is in fine condition but the outer pulleys will spin on the rubber (could be the rubber spinning on the hub) and the "stops" will contact each other.

 

[diesel4me]

I'm no expert,but I'd guess the balancer is junk if the rubber bond has been broken...for the 70 bucks a new Dorman balancer costs,or a bit more for a GM one from Rock Auto,I'd say it would be best to ditch it before it causes some real greif...it might not make the crank break,but at the least it could chuck the pulleys or belts off and trash the 400 dollar radiator..

Both of my 6.2's sound just as you described,I have never really inspected the balancer on either of them...they could be just like yours for all I know..one truck has a additional pulley bolted to the damper for the plow pump,which does not run 100% true,I dont know if its the pulley itself or the bolts,the spacers,or the balancer itself..

I do notice the V belt for the altenator will flop wildly on both trucks between the altenator and crank pulleys on the "slack" side (the side of the engine facing the passenger side)--unless you tighten the belt really tight,it whips around a lot,and tends to squeal and slip easily--I think it needs an idler pulley there that was spring loaded,but GM never put one there..probably why they went to serpentine belt setup instead?..

I dont like tightening the belt too tight,it strains the water pump and altenator bearings..it could be the balancer moving around as you described that makes the belt whip like that,and the clacking at idle being eggagerated possibly..or just the firing impulses typical of a diesel engine?..

 

[Massboy]

The problem is all the dampers listed are not the same as this one. This is a specific 3 groove pulley mounted as part of the damper and I cannot find the part number for this. I know it is almost 3 times the cost of the other dampers but still, I can't find it. On GM direct they list a 3 groove pulley and a damper but I don't think it's the same one as the damper is just over $140.

 

[Massboy]

Did some more digging and found out it is a rubber dampened 3 groove pulley that's mounted to the balancer behind it. The pulley was designed for longer belt life with the 6.2 and is repairable. I spoke with John from Damper Doctor and he repairs them for $284. It seems there is a bearing in the pulley plus the rubber. He said it's main purpose is to help the belts from abruptly stopping like the crank does when the motor is shut down. The momentum of the belts, pulley, water pump was believed to put extra strain on the crank and the harmonic balancer. If your motor "cackles" a lot at idle and has that metallic sound at shut down you might want to look at the bottom pulley and see if you have the same type of pulley as mine. John said if you have those noises the pulley is bad and absolutely should be repaired.

John @ Damper Doctor
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[diesel4me]

Huh!....I always assumed there was only one type of balancer on 6.2's.
Maybe only the military engines used that one you have?...bet it took some research to find out about your damper being unusual..

I'll have to check the two on my trucks out,and the one on a parts engine I have with a snapped crankshaft and see if they look like yours--..

Offhand I'd say no,I am pretty sure all of the harmonic balancers on my engines dont have 3 pulley sheaves ,and they have 3 bolts holding the pulleys on (I think!)..at least my pickup only has 2 sheaves I'm pretty certain, because it has no A/C,and the previous owner would not have added a separate pulley for the plow pump if another sheave was already there that could have been utilized most likely..
My Burb had A/C and may have different pulley arrangement..The A/C compressor was missing on it when I got it--I used the sheave that would have run that to power the plow pump on it..

 

[Massboy]

It is the same balancer just a different rubber isolated pulley on some bolted to it. I guess it's only the 3 belts ones that have AC. Your burb that had the AC might have this same pulley.

 

[Massboy]

Found out more info on these pulleys. They are part # 15592128 and can be located quite easily on the GM part sites. They are OEM and you get a 1yr warranty. I just ordered mine for $226 delivered. You do have to look around as some still sell them for the GM list of $430+.

Doing more research it is the cause of the loud clacking sound I'm hearing for sure as many have complained thru the years of the noise. It will be nice to get it as quiet as it can and should be.

 

[Richcz28]

86' Harmonic Balancer

My pully bolts to the balancer. It is a standard steel pully as best I can tell. I just did this job last week.


The pully bolts onto the balancer with 4 bolts. It is a 3 belt pully.

 

[KirsL]

The main 6.2 and 6.5 use the same balancer. The different part is if a spacer is used on the crank snout or not. The spacer is needed on mechanical engines. Any of the V-belt or serp belt pullies just bolt to the face of the balancer.

Big thing with the 6.x engines, if you suspect the age or condition of the balancer just change it. A basic stock one is cheap enough to just do it. If it takes a crap on you it will break the crankshaft in time.

 

[Massboy]

I actually titled this thread incorrectly as it is not the actual balancer I was talking about or the pictures I show. What I show is the rubber isolated 3 groove pulley that was used on 1985 and later 6.2's with A/C. It bolts with 4 bolts to the balancer. The CUCV engines and other 6.2's without A/C use plain steel pulleys mounted to the balancer. Even the Humvee's use a steel pulley with 5 or 6 grooves I think but do not use this same pulley.

The purpose of this pulley is to keep belt oscillation to a minimum and prolong belt live. It is also supposed to prevent the shock load that a A/C compressor can put on the crank when abruptly stopping like a diesel does. You would be amazed at the "clacking" sound generated when idling from this pulley because of the oscillation of a diesel engine.

 

[Massboy]

Got in my new pulley today and installed it. All I can say is wow! The clatter is absolutely gone and my truck is extremely quiet for a diesel. If you look at the picture of the rear of the pulley you can see where the metal has been hitting and that is where the noise comes from. I can see from this recent picture to the one I took when I started the rebuild that the rubber has deteriorated more since just by running it what little I did.

What a difference this pulley makes. This is a OEM from GM with a one yr warranty. Very happy with the results.

 

[brett37]

Another option

I don't know if you guys heard of fluid damper but these last for ever never need replacing buta few dollars 400 just thought I would le you know thanks.

 

[longbedder]

Interesting - I didn't realize that the 6.2L ever came with that type of crank pulley.

I used to worry about my V-belts going flippity-floppity (my 6.2L in my pickup has a plain old steel pulley)...but they don't loosen up or wear abnormally so I've learned to live with it.

The 6.5L with serpentine all come with a dampened pulley like yours (but obviously with different belt grooves). The one on my Burb failed and I thought something major-league-bad had happened due to the sound...boy was I relieved when I found out it was just bad rubber and got a new one for $60. Crazy that the V-belt version is so much more.

As an aside, I do run Fluidamprs on both trucks. To me it's worth not worrying about the rubber failing on the harmonic balancer (and not having to replace them every so often).