FAQ: Supercharger Noise (Bad Coupler)

You know, it's funny that we're on the topic of superchargers. A "computer major" friend of mine just got a job with Eaton. The conversation went like this:

Him - "I just got offered a sweet job."
Me - "Where at?"
Him - "You probably never heard of them, Eaton."
Me - "Do they make superchargers?"
Him - "Yeah, how did you know"

Superchargers are the most basic and reliable forms of forced induction; there's no way it could break except for couplers and the rotor coatings being stripped.

By the way, does my '95 have an M62? I forget the number...me and my stock 2.8" pulley...

And it is kind of 'known' amongst mechanics that these superchargers 'go bad' at 100K miles or so. Usually because nobody ever checked the level of the supercharger oil, one of the most overlooked maintenance items on all the Eaton SC'd cars.

Check that SC oil, change it if you haven't lately!!!

OTOH, keep the SC oil filled where it belongs and the only thing most of you will ever need to worry about is the coupler.

this is one of 2 things people have hassled me about when i say that i am going to get a 96 riviera, so if i was to bring the car in for checking before i purchase it should i ask them specifically to check it? the car has 51,000

You can check it yourself. Unscrew the fill plug (front side, black Allen key), oil should be up to lowest thread of the hole. But at 51k, it's due for changing. See write-up:

Changing Supercharger Oil

Listen to your supercharger at operating temperature. If it rattles, or sounds like "marbles in a can", the coupler may be worn. This is somewhat normal when the engine is cold.

Using a star socket/ratchet, loosen tension on the SC pulley, slip the belt off, and rock the SC pulley back and forth. Should be no more than about 1/8" travel in the pulley. If it feels really loose, you need to replace the coupler. The part is only $35, but it's a bit of a job. Have a specialist do it, or reference the coupler write-up in the above link. After checking the pulley, make SURE you align the belt correctly around the crank (large, bottom) pulley when you put it back on.

There is a lot of misinformation on superchargers out there. My mechanic thought they would last a long time but had been told by dealers that when they start to "rattle" they could only be replaced as a unit. Of course the "rattle" is the coupler. I took a ZZP coupler kit to him and they did the work.

He has done several coupler changes since for other customers instead of screwing them for a new supercharger. They are a good shop.

Did my snout coupler, belts, and pulleys during this past week and finished up this morning . In total I may have spent 5 hrs on it?? But I take my time and don't rush anything, and had something else to drive to work also. Buy your own parts, supply your labor and tools, and save a bundle. Figure I saved $500 + in parts and labor costs.

Well, due to my ignorance probably, the bearing in my supercharger is stripped and I allegedly need to replace the supercharger. It had been making a rattling sound for a while. At least, something had been rattling under the hood. No warning signs. Nothing. I just pulled the car out of the garage to wash it yesterday, tried to start it back up to get it back in the garage, and it just... wouldn't start.

Anyone know if a supercharger replacement would be the only way to go, or what? Just want to make sure, because we sure as hell don't have enough money to purchase a new one.

How do you mean, it won't start? Does it turn over but not fire up? Or is it just plain dead when you turn the key? A failing SC won't keep the engine from starting. That rattling sound, if from the SC, is typically due to the snout coupler wearing out and becoming loose. It is very easily replaced, with a $30 coupler from ZZP and a couple bottles of SC fluid. Did a shop tell you the SC needs replaced? That is a shop or dealer's normal procedure, as they don't service superchargers.

Can you hear it trying to turn over? Walk out into their shop, tell them to tension the supercharger belt and take it off, then call them liars to their faces.

It's trying to turn over. It's not plain dead. A new coupler and SC oil should do the trick then?

Here's what I'd do:

Detension the SC belt with a Torx bit and ratchet. Slip the SC belt off. Now, try turning the SC pulley with your hand. It should move very easily, without making much noise. It should not grind or be difficult to move with the belt off. As long as the blower is turning without issue, you know it's not the cause of your problem.

While you have the SC belt off, you can remove it from the idler pulleys and carefully slip it between the crank pulley and engine mount, so that it doesn't contact any moving parts. Use zip ties or some other means to secure the belt out of the way, to something on the side of the engine bay. Start your engine and drive the car. It will not be nearly as powerful, but should start and drive okay. If you're still having problems, it means the blower isn't the problem. If you're problem goes away, it DOES NOT mean the blower is responsible. There are other factors that could cause problems under boost, such as fuel, spark, or transmission.

Yep, take the SC belt off and it should start and drive normally. If not, you've discovered that the SC is not your problem.

Just got done doing that actually. We've got it running now. My guy says now that he thinks the bearing is damaged and the supercharger may "fail" and not be reliable, and so on and so forth. Should that be a big issue?

Can you spin the SC by hand?

You should be able to pick up a reasonable condition used SC on just about any 3800 site for short money. couple hundred, maybe $300. As long as it's a series II. What year car are we talking about here?

Yeah, it's a 98. The labor charges are the main thing. I'd be paying more for that than the charger itself. Anyway... I believe my mechanic spun it by hand. I'll call him up later tomorrow to be sure. I'm back at home now and won't get back up there till Sunday though, so we can give it a go then.

Just a reminder that of all the times we've heard noises coming from our superchargers, not once can I remember it being from bearings or ultimate supercharger failure. These Eatons can sure take a beatin!

ZEP wrote:

Yeah, it's a 98. The labor charges are the main thing. I'd be paying more for that than the charger itself. Anyway... I believe my mechanic spun it by hand. I'll call him up later tomorrow to be sure. I'm back at home now and won't get back up there till Sunday though, so we can give it a go then.

There are alot of knowledgeable people here, it wouldn't take much for you to be able to swap blowers yourself (if yours really is shot)

Just got done investigating it today. We can turn the pulley with no problem, but it has a bit of play in it.

We found some metal shavings that seem to have popped out of the supercharger around the pulley, and the mechanic says it was making a loud noise when he got it to start today. He tells me it was coming from the stout of the blower about an inch away from the pulley, so he just assumed the bearing was shot thanks to the noise and the metal shavings.

Now though, there's no noise and the car starts without issue. We're going to drive it around for about a week and see if the problem comes back.

i just changed the supercharger in my 95. look on ebay for a store called abc supercharger. cost me 220.00 plus 20 for shipping (does have a 150 core charge) has a bit of a wait but well worth it. tried coupler and new snout but lots of play and noise. i could hold the blower in the air and shake it and hear rattling, sounded like the engine was trying to come apart when driving, totally fixed now

With a press you can replace the bearings in the snout yourself. I've done it and it's over all not a bad or tough thing. Just need a press.

If you are looking for a replacement there's a guy on the bonne forums selling one for ~$200 possibly ported.

www.nebonnevilleclub.net is the url. I forget if the owner still has it set for can't read w/o login.

Awesome, I'll keep that in mind if i do have to replace the thing. I actually drove it to work yesterday. It worked perfectly fine. This is probably the strangest issue with any car I've ever had. If it continues to work fine, maybe I won't need one after all :/

as others mentioned..they are quite strong and don't usually have an issue.

What pisses me off though is the fact that the day it first goes out again, I run over two damn staples in the road and the tire deflates overnight in my garage!

And here I thought I had established some kind of bond with the Riv. She seems to be trying to commit suicide :S