FAQ: Supercharger Noise (Bad Coupler)

Rickw wrote:

You said you de-tensioned the SC Belt and the noise went away. What else is driven off that belt.?

2 idler pulleys, the tensioner, and the balancer. Those are the "possibles" related to that belt system.

I've disconnected the s/c belt and the noise was gone. I'm almost positive it's the two gears driving the impleller.

To answer some questions:
yes the impellers pulled out. I couldn't turn them at that time. I was able to seperate the snout, and push the rotors back in place. Then they'd turn fine...no snagging...

The oil is full and color good, no leakage

The belt noise is gone (for now)

HOWEVER... I have two theories...

1: possible problem with new coupler...broken...out of round...I will pull off and see

2;.... and this is the big one.... when I took the snout off, some of the UIM gasket was attached to the bottom of it. to clean up i cut out that little bit of gasket that sits under the s/c. Now it's thin yes, but not super thin. I wonder if now the snout is just pulled down that little bit past true horizontal because the gasket isn't there to prevent it from bending. this slight bend is causing strain on the coupler/gears and makes a noise... a wobble.... I have to open it up to see...

I do plan on putting a piece of aluminum under there...source? Miller light can. A piece cut and shaped to snout dimensions and folder over to be thick enough... then reassemble and see (after I've checked all other areas too)

That's part of my weekend plan...the other..change the brakes on my Si.

thanks amigos!

I should also note, at park or neutral, the noise is far less.... does putting in drive engage something?

took off snout, put washer under the vertical bolt...refilled with oil and strarted...still makes noise..

now belts are making a racket too...

I think I'm about done with this Riviera and it's time to get rid of her...working on her today, I felt like I was having just no fun at all..I don't owe any $$$ on her, so it's just work to keep her running...how much more????

I'll deicide in a day or two.

I'm truly sorry I can't help you, Nate, but you've got me stumped.
My theory went out the window when you confirmed that the noise is at the snout end of the blower.

Right about now is when AA or Albert or Deek or Rick should be jumping in with the answer...

And I think it was mentioned before, but a video with good audio would probably help jog someone's brain.

I lost one of the bolts too...right now my engine has two phantom bolts in it's crevices somewhere!

The s/c oil was black and nasty, and considering it's only 3 months old...that's odd. I wonder if the oil they sent is too "watery"

When I had the snout off, I turned the impellers by hand...they spin fine, no catching or hard spots, I don't see any wear on the gear teeth..

The belts is probably the alternator needing some "wiggling"...so I'll loosen it and readjust it and the pulleys...

My only other theroy is the bolts holding the snout arern't evenly torqued...perhaps the snout is still out of alignment. The coupler is on tight and appears to be concentric and undamaged..

where besides GM can I buy S/C oil? what else would it be known as? I've one full bottle of GM oil, but that's not enough....

Natesriv wrote:

where besides GM can I buy S/C oil? what else would it be known as? I've one full bottle of GM oil, but that's not enough....

Only other place that I know of is zzperformance, or one of those websites. But then you have to wait for it.....

Nate, last weekend I changed the coupler in my S/C. However, mine was so worn out, it simply fell off. My gasket also "split" on the bottom, but I left it in place and put it back. You should tighten the snout bolts first before tightening the one that bolts to the LIM. As for the oil being nasty, can't help ya. Only way it could get that dirty that fast is....
A) The gears are wearing quickly,
B) You have an air leak on the mating surface of the snout that's sucking air. I remember you saying it wasn't leaking, but if the "leak" was at the top, it wouldn't leak fluid....in theory.
C) Perhaps one of the bearings behind the gears has broken/shifted, causing intake air to intrude into the snout, which would also turn the fluid black. This would also explain the noise??? (This could also cause problem A)

As Eldo said, wish I (we) could help. Without being there to hear the noise or see what's going on, it's near impossible to diagnose.

I'm going to look a litle deeper... reading on the boost control solenoid, and how it operates... The sound is much less in park..put in drive and it's worse...

To test S/C noise I tied a string around the pulley, and wound it up. Pulling on the string turned the s/c pulley at a moderate speed... no sounds, no warble...

I've read that upon startup the solenoid and boost valve can make some noise...

Need a new solenoid perhaps...not sure...

oh, and three salvage yards in KC...one red Riv, series 1 I think...no 3.8 supercharged anywhere!

does anyone have a link or the part number to the boost control solenoid??

Natesriv wrote:

does anyone have a link or the part number to the boost control solenoid??

Believe me, you don't want to open that can of worms right now... If you want to eliminate the possibility, just unplug it and plug the hose that comes from the manifold.

It sounds to me like the snout bearings might be gone. The good news is that Gen 3 superchargers and snouts are cheap and easy to find. Try swapping snouts with someone nearby. There are a lot of surplus Gen 3 blowers around as people tend to want Gen Vs or ported Gen 3s.

That's the next troubleshooting step I would take.

I dont' understand what you put a washer under.

three things..

1: when I unplug the boost solenoid...nothing...no change, car runs, vacuum bypass moves with throttle.... no effect...should there be?

2: the horizontal (bottom) part of the snout, the place where the bolt goes vertically into the UIM. Put a washer there.

The damn belts are still making noise too... The only thing I did this last fixing time, was remove the alternator to get the snout off....put it back on and now there's a scissor choppin'ish sound...whik whik whik...wtf! That alternator whines too I thinkl.. I may see if swapping with new removes both...if so, I'll get another.

3: The noise isn't coming from the snout, based on my sense, it's right around where the two gears mesh together....


do they sell just the snouts?

drives fine, just went for a spin...no problems, just loud!

No, some light play with the throttle would still do that. I was only suggesting disconnecting it (and plugging the backpressure line) because you were wondering about it, and because we're still working deaf here. Also, I thought the different noise in Reverse just might be related... I can't think of anything else that would explain the noise being worse in Park, except the normal slight increase in idle speed.

Are you sure you've got the belts sitting in the pulleys correctly, especially the crank pulleys?

belts are fine... I'm becoming an expert in taking them off! I think it's the alternator...I can go to Oreilly and swap out...try it and see if it still does it.. that alternator is a 4 minute job to take off...getting good at that too!!!

what does the solenoid do then... I unpluged and blipped the throttle and and didn't see any effect... I would also suspect that a defective solenoid would trip a OBD code.... nothing like that (but my ABS/Traction lights are on...wheel hub I think)

it does sound like a rattle in a can...I was wrong eariler...it's just a rapid rattle...almost sounds like a diesel at idle...you know..that sound?

But everything I've done to check the gears and impellers shows me they are not bad...they spin quite freely, don't catch and there's plenty of oil in there...

still looking...

check these out...this is exactly the sound

1: https://www.youtube.com/watch?v=Ts3B9TMpwx8&feature=related

2: https://www.youtube.com/watch?v=CL_yj3q7264&feature=related

Doubt there's a rebuild kit either...

anyone ever have this? The coupler is new, tight as a drum...

As long as you plugged the lines that go to the BCS and it didn't make any difference in the noise, then we can cross that off the list. Plus, if you've decided now that it is a more rattling type sound, I think we're running out of possibilities except for the gears or the ball-bearings, either in the snout or behind the gears...

I know the snout is new, but If you can't get a hold of a stethoscope, you should at least work your way from the end of the snout back to the front of the rotor case with a large screwdriver, pressing the handle end to your ear (and being very cautious of hair and clothing!)

do you sell these stethoscopes? LOL

I'm not going to give up on this Riv... she's too smooth when she runs right..

BUT, I've a couple of questions:

1: Can you remove the innards of the s/c wthout having to take the entire s/c off? I see that the alternator bracket prevents the impeller plate from coming out completely, but if I remove that alternator bracket, it looks like I can then remove the impelers all the way..

2: Is there some rebuild kit/way to rebuild the bearings of the two gears and the needle bearings. I don't think the snout bearings are bad.

I want to do this to bring extended life to the Riviera...it seems simple!

I think Intense and ZZP both sell bearing/rebuild kits. here's ZZP's parts page: http://www.zzperformance.com/grand_prix/products.php?id=106

I am not sure if you can do the rebuild on the car or not, sounds like to do the bearings and snout over you may be able to.

They are selling the snout bearings, although I think that the larger of the two is also the same as the front rotor bearings... Regardless, I don't think that the rotor bearings are a DIY job. Do some Googling - you need the tools & talent to take things apart without cracking anything, and then put them back together exactly right. The rear needle bearings are even trickier.

If you determine that the rotor bearings are indeed bad, and not the new snout, I think that the easiest thing to do would be to swap the whole "rotor pack" out with a donor from a used blower bought cheap...

you know...i do have a P&P gen 3 for sale with a 3.4
already has the right vac port for a 96 too!

Just out of curiosity, who is "P&P", and what is the "right vacuum port for a '96"?
I thought that '96+ all had the same motor and cruise control...

P&P= ported and polished

The 96's use the same s/c as 97+ except we have an extra port opened up (front by the BBV) for a vac tree because our transmission is vacuum controlled.

Edit: but it's really not that hard to "T" off one of the other lines if you put a 97+ s/c on a 96.

well. I see zz's stuff... looks like about $70 for all of it...good price. But I've not skill or ability/tools to pull & press bearings.

Can you remove the innards of the s/c only without taking it off entirely? I see the alternator bracket gets in the way, but that can be removed... would I be able to pull out the inside that way??

Does anyone know of anyone in KC area, or anyone who I could mail part to should it need to be fixed?

With your guys help I believe it's the bearings on those two gears... there's a little slop...

think Ed Morad has the inards?

oh and if the entire s/c needs to be removed, looks like the fuel rails and injectors are in the way...

hard to remove?

whew!!!