: My crank pulley is wobbling...



danbuc
08-13-05, 04:03 PM
what should I do about it. It doesn't seem TOO bad, but you never can tell. It appears that there is about an 1/8" variation between the furthest point from the block, to the closest point. I know the wobble isn't good but is there really anything I can do about it, other than getting a pulley puller, dropping the cradle and a pulling the old one off, and installing anew one which will be a HUGE pain in the ass. I took a video of it. You can't really tell that well, but the slight knock that I have seems to correspond very well, with the pulley's wobble. Here's the link. http://www.putfile.com/media.php?n=MOV006129 . I couldn't find any cool places to host it, so I found this simple site called putfile or some crap. On a side note, this knock is not internal, and is somehow associated with a timing component. The shaft (well crankshaft that is) that turn the pulley also drives the chain that turn the intermediate sprocket (which in turn drive the two timing chains,..ect). The knock is coming form the area behind the cover plate which conceals the intermedaite sprocket and timing chains and trensioners. IS it possible that this wobble has maybe damaged a tooth on the intermediate sprocket, or possibly affected the chain? The car runs like a champ so I'm not too worried right now. Just curious if I shoudl replace it all now and get it done with before something important fails catastrophically which I really don't want to have happen.

Mark Bunds
08-13-05, 05:47 PM
You really need to get that checked out. It may be nothing serious, it probably IS nothing serious, but if one of those timing chains lets go for ay reason, the pistons will come into contact with some of the valves, and that will be the end of that. There is little chance that you can rebuild the engine once that happens.

danbuc
08-13-05, 05:51 PM
I'm well aware of the consequences of a timing chain letting go on an interference engine such as this....but no one can seems to tell me what it is. Perhaps it is the movement of the shaft that the balancer mounts to, which is causing the knock. I'm sur that the wobble hs worn the seal away at least a little bit. It's doesn't leak any oil though, so it coulnd't be too bad. I guess my first step is to replace the balancer an go from there.

zonie77
08-13-05, 06:22 PM
As nice as it was to have the video I still couldn't be sure how much wobble there was.

This has come up before. If you take the belt off and run it, are the machined grooves straight or wobbling? B-b-o-b said they weren't always true to the outside cast edge ( I would've thought they'd at least get them close ). The grooves were machined to the shaft hole. You have to check that. If it is wobbling it means the bond is breaking between the two metal halves.

danbuc
08-13-05, 06:27 PM
No, it's definitely wobbling. I think that the outer section with the belt grooves may be starting to seperate from the cushiony rubber material in the center. I say this because whe I look at it (not the video, but the car itself) the center portion doesn't seem to move at all, but the outer portion does. I will try running it without the belt on to take a closer look. While I'm doing that, I might as well take another video..hehe.

Mark Bunds
08-13-05, 06:46 PM
According to the diagrams of the 1998 N*, the crank pulley (harmonic balancer) is bolted (duh) directly to the end of the crankshaft. If the bolt is tight, it seems unlikely that anything other than end play of the crank would cause your pulley to move in and out, and that much end play would be a bad thing. If the bore of the balancer is worn, (also unlikely) it could wobble. If the balancer is built with the typical rubber insert between the balancer hub and sheave, it is quite common for the sheave ring to run out of true with the hub.

So, is the wobble constant? It's hard to tell by the video if the same point on the sheave ring comes around each revolution. If this is the case, but the hub is running true, then the insert is merely slightly warped, and the knock is coincidental. However, if the bolt or the face of the hub is wobbling, the the bore of the balancer or the end of the crank is worn, which is very unlikely.

It is also unlikely that the wobble of the balancer itself has caused the knocking, but is probably more a symptom of something else.

In any case, the only way to tell is going to be to remove the front cover and have a look.

Eldyfig
08-13-05, 07:15 PM
From the video it doesn't look that bad, hard to tell. Compared to mine, anyhow. Mine has been like that since I got the car in 2002.

The pulley is a casting which gets the mounting hole and grooves for the belt machined on it. Then it is balanced. The face of the pulley is not machined and it can appear to wobble. Look at the belt itself instead of looking at the face of the pulley. If the belt doesn't wobble then there is nothing wrong with it.

Ranger
08-13-05, 08:22 PM
No, it's definitely wobbling. I think that the outer section with the belt grooves may be starting to seperate from the cushiony rubber material in the center. I say this because whe I look at it (not the video, but the car itself) the center portion doesn't seem to move at all, but the outer portion does. I will try running it without the belt on to take a closer look. While I'm doing that, I might as well take another video..hehe.
I think you hit the nail on the head. It's called the elastomeric bond. I would be concerned about that thing being out of balance at 2000 rpm much less 6000 rpm. It can only get worse.

danbuc
08-13-05, 09:24 PM
Hehe..yeah I've seen first hand what happens when they go bad. One let go on one of the T-Buckets that the Hot-Rod class was testing on the dyno. It put a whole in the wall, that's all I'm sayin'. There's isn't any endplay in the crank as the bolt doesn't wobble or move in and out. I'm gonna take a better look at it tomorrow morning and see if I can maybe get under the car so I can tell if that "elastomeric bond" as you so stated Ranger, is coming apart or not.

93sts100k
08-13-05, 10:35 PM
my pullley wobbles alot worse than that and has for several thousand miles. no knock though. ive also looked at several others and seen the same or worse, and ive seen some w/no wobble. i would like to hear more input on this. im about to pull my engine for the gaskets and if i need to fix it i will

Eldyfig
08-13-05, 11:43 PM
Is the belt or grooves wobbling or not running straight? If they are running straight, it is just the casting.

danbuc
08-14-05, 12:42 AM
When you look closely at it, it kind of seems that the belt moves back and forth across the surface of the pulley. I'm gonna have to take a closer look tomorrow and see if I can get a good look at the entire balancer/pulley assembly.

lry99eldo
08-17-05, 10:44 AM
This thread is getting dated, today is the 17th so you may have done more and or fixed the problem by now.
What I think you are seeing is called lateral runout. It runs in paralell to the shaft, as opposed to axial runout, which is the difference of how two surfaces based on a common axis are in position to each other. In this case, the functional part of the balancer, the grooves, should be concentric to the crankshaft axis, or crank hub. In concentricity, the relationship is to the axis in ALL directions, around and back and forth. A balancer's functional charateristics should never be more than .008-.010 inch in any direction to the crank hub, i.e., centerline of the entire crank axis.
True, that as an assembly, there may be some casting inaccuracies, but they should not be so much so that it is noticeable to 1/8 inch, (.125).
The elastomer band that is used in most production balancers does wearout, deteriates, gets soft or hard due to any number of chemical exposures and or heat cycles, or just may have been bad from the get-go at assembly but OK enough for it to have passed balance procedures.
The only true way to determine this is to place an indicator, or two if you have access , to measure the total indicator reading,(TIR) in both directions in relation to the axis of the crank. This would be at the functional surfaces of the balacer that are machined, the grooves. If they are more than mentioned, replace the balancer.
The key word here is "Harmonic". The MAIN function of the balancer is to maintain near zero affects of the crankshaft as it rotates and sees an incediable amount of twisting and other mechanical forces as the engine cycles, known as harmonics. The running of accessories is secondary to it's existance.
A balancer in the condition you describe can be destoying your engine in ways you would never notice until complete failure or may give you warning as it approaches failure. And as mentioned, when one blows apart, it's not selctive as to where the parts go. It's not only destructive but very dangerious, and if it does blow up you will know it!
It all boils down to this; Replace it if the test indicates the runout described and or excedes factory specs. Do not mess around with this matter.
lry99eldo

Mark Bunds
08-17-05, 11:26 AM
A balancer in the condition you describe can be destoying your engine in ways you would never notice until complete failure or may give you warning as it approaches failure. And as mentioned, when one blows apart, it's not selctive as to where the parts go. It's not only destructive but very dangerious, and if it does blow up you will know it!
It all boils down to this; Replace it if the test indicates the runout described and or excedes factory specs. Do not mess around with this matter.
lry99eldo

That's what I'm talkin' about! A concise answer to a concise question! Thanks lry99eldo!!!

danbuc
08-17-05, 11:29 AM
I'll be bringing the car into the shop at school in two weeks. They have a bunch of dial indicators there that I can use to measure any runout on the balancer. If it's excessive, then I'll probaly have to wait another three weeks before the next open shop when I can replace it, since I'm not going to the dealer for this. Since I'm planning to flush the tranny fluid and replace the shift solenoids, I'll have the car on the lift, so I can check the balancer at the same time.

inmycadillac
04-24-07, 03:06 PM
:thepan: so uhh, what's the verdict??? I just found out I too have the exact same problem. I tore up a belt and after replacing it looked at the performance of the pulleys and found the crank pulley or "harmonic balancer" to have a significant amount of play. NOT GOOD! Will someone with expierence please reply. My major question is this...will replacing it fix the problem or will it happen again?? Basically is my beautiful car done for??? PLEASE HELP!!:confused:

dkozloski
04-24-07, 03:30 PM
If the dampner hub is loose the engine would have seized long ago. Squeeze from the hub bolt through the dampner hub clamps the oil pump gear. If the hub is loose the oil pump quits turning.

Ranger
04-24-07, 04:00 PM
It is probably the elastomer bond between the two parts of the pulley that has failed. Replace the pulley.

danbuc
04-24-07, 04:55 PM
It was along time ago, but when I measured mine, the lateral run out was within acceptable limits, and the belt never wore excessively or broke. If yours tore the belt up, I think your gonna need to replace it.

inmycadillac
04-25-07, 02:31 AM
Thanks dudes. Ranger, I did read your other posts about the elastomer bond and told my mech bout it. That's exactly the problem!! Thank you so much. He's got his own business and hasn't seen one go bad as a result of that before. So telling him I found others on here that have had that issue made us both reassured. And my crankshaft is fine. That's what we were really worried about(worst case scenario). Again, I'm replacing it Thurs. and will let all know the results.:thumbsup:

1putt
01-27-08, 09:04 AM
Dont mean to rekindle this post but I came across this.....

"In 1995, GM revised the original crankshaft balancer to provide smoother operation and longer durability. If the balancer is removed from the crankshaft for any reason, GM recommends installing the newer, improved balancer (P/N 12552437 or 12552436, depending on the engine). "

I have the same situation brewing and was wondering what the cost of replacing the pulley would be? dealer or independent or DIY?

thanks

tateos
01-28-08, 08:34 PM
The balancer is pretty cheap, I think - maybe around $50-60 at Rock Auto. The labor cost could be pretty substantial - I have to believe a few hundred bucks. Getting the bolt off is damn near impossible, and then the balancer is pressed onto the crankshaft and has to be removed with a puller - not easy in the car - gotta drop the cradle some at least

JC316
01-28-08, 10:32 PM
Heh, I put a new one on from Oriellys and two days later, it twisted off, so I had to get another one.