Balancer Bad?

[kconnair]

My '87 Suburban (LD 6.2) started making a loud noise at low idle - almost like a rattle. Seems to go away as soon as the throttle is advanced. Not a rod knock, and doesn't seem to be a main knock either.
It makes a loud "kick-back" noise when you shut the engine down. Wondering if this is the harmonic balancer going bad? Or maybe the timing chain? Checked the clutch fan for a bad bearing, the alternator sounds ok (used an automotive stethescope in a couple of areas, and just can't localize it). Seems louder under the truck near the balancer, but it really is hard to tell.

Any Ideas on this one, I am leaning towards replacing the balancers on both trucks anyway, but I am just wondering if I am heading the right direction on this one.

Thanks,

Kevin.

[dieselbegreat]

Sure sounds like it could be to me. It happened to my 88. The keyway on the crank was all scored and the balancer and pulleys had rotated on the crank making a severe vibration which would shake the whole truck pretty good at idle. I had to have the crank repaired and now it's no problem, but you have to remove the balancer and pulleys etc. to find out.

[kconnair]

:confused:
Except for the noise, there isn't any additional noticeable vibration. It almost sounds like a bad A/C clutch , but the A/C clutch is ok. Truck runs ok, but not quite as well as my vin J suburban does (emission controls part of that, I'm sure). Anyone have any additional ideas, or confirmation about the balancer, or is it just a good idea to replace it. The engine has around 120k ~ give or take a few thousand.


Thanks,

Kevin.

[kconnair]

When I disassembled the accessories from the engine, I discovered that the rubber isolated pulley assembly was bad. That was the source of noise. The balancer appears to be in good shape, no obvious cracks in the rubber in the front, and the rubber does not appear to have drifted.

My next question, I have another pulley assembly, but it is different from the one which came off the truck. The innermost pulley is a different diameter - I'll need a shorter belt, and the air conditioner will spin faster. I wonder if this will be a problem.

There appears to only be one pulley assembly available from GM at this time too.

Any ideas?

Kevin.

[wthif]

Also keep in mind what else the belt is driving. On my truck the belt that drives the AC also hits the Power Steering Pump. So the inner two pulley diameters need to be the same and so do the pully diameters on the power steering pump because there is that single belt the goes to the power steering pump. The two belts that hit the power steering pump need to be doing the same revolutions per minute. If your setup is different, you can ignore what I just said. I have a pulley I bought to replace mine and ended up not going with it because I decided to stick with a stamped pulley instead of the one with rubber. My pulley also has the inner two v's the same diameter. The part number off the box is 15592125. I'm also looking to get rid of my extra brand new pulley. ;)

[kconnair]

Oh man,

I had not thought of that. My PS pump has 2 different size pulleys - one acts like an idler for the A/C unit, and the other drives the PS pump. The crank pulley assy. has 2 different sizes too. I'm probably going to have to change the PS pump pulley. Damn.

Kevin

[spitfirenut]

I may be confused here, but if it's an idler pulley you are talking about it won't change the speed of anything except the bearing that it rides on. The idler just changes direction of the belt. The pulley on the accessory is what controls the speed of the accessory.

I may have misread the post is it the pulley that mounts to the balancer or an idler?

[ 04-10-2004, 06:25 PM: Message edited by: spitfirenut ]

[cubby]

Change the balancer. Or you might be looking at a broken crank later. Happened to me :mad:

[kconnair]

Thanks for the info so far,

I have a new replacement balancer, which I was going to use anyway, but the pulley thing is a problem. The PS pump has 2 pullies on it, and one acts like an idler for the A/C compressor, but that pulley does not free wheel. I looked at my other engines, and found that the P/S pump and Water pump pullies are different than those on the Suburban. I guess I will have to change them both to get this thing to work.

Kevin.

84 "J" 3/4 ton Suburban
87 "C" 1/2 ton Suburban

[kconnair]

I was wondering if I can get a few descriptions of the rubber isolated crank/harmonic balancer pulley assemblies out there, and if anyone has gotten a replacement.
GM has only one listing (for the V-belt style), but I have two different styles of pulley assemblies. My shop manual is no help in this area.

The one on the truck has a large outer pulley, a smaller middle pulley, and another larger innermost pulley. On another engine, the outer pulley is large, and the other two are an identical small size. The P/S pump pulley and water pump pullies match the balancer pully set. :confused:

Any help would be appreciated!

Thanks,

Kevin.

[dieselcrawler]

Here's my question: My truck has about 100K on it, and I get the impression that it may be a good idea to replace the harm. damper as preventitive maint. Any thoughts on this? The best place to get one, and reasonable prices? TIA,
Greg

[kconnair]

I have seen new balancers for around $95-100 new. They list much higher. I paid a little more than that for mine, but I needed it in a hurry (I thought), and then found the crank pulley assembly was the problem.

I still need someone to tell me what a new crankshaft pulley assembly looks like at least as far as the configuration of the pullies & their approximate diameters.

Thanks

Kevin.