Embarrasing noise from my sc

MtDewd

Registered User
I've been trying to get to the bottom of this noise coming from my supercharger. It knocks like a plastic screwdriver handle in a blender on low. I'm very proud of the sound my exhaust makes. The motor sounds like a V8 and has lots of lope, but now I'm embarrased to drive it anywhere because of this knocking noise in the supercharger. It is very noticable inside and out of the car.

I took the sc belt off and it goes away. When I turn the pully back and forth there is a little play in it. The play is about 3/16 of an inch and when I do it fast I can hear that that's where the rattle/knock is coming from. What do I need to do to make it go away? It was just magnaported and rebuilt about 1000 miles ago. It knocked before the rebuild also.
 
I am no expert on superchargers but...

It would sound to me like your rebuild didn't include checking the gear drives for the lobes!! Too much play indicated worn out gears in the SC. I could be wrong, but my old supercharger off my 89 SC did the same thing. Are your running an O.D. pulley? Mine had a 10% OD pulley and I didn't know about it till I changed the supercharger a few days ago, I guess that would expain the 15 psi of boost I was making huh?

Anyway, you might want to check with the rebuilder and ask them why they allowed that "knock" in the SC to go unchecked? Also ask them if they ever checked, or if there is a measurement for wear on those gears in the SC.

Good luck, tell us how it works out.

Phil Stocker
 
I think it's just a worn out or broken coupler, which is the part that connects the snout shaft to the rotor and gearset. The older ones had a spring loaded style to absorb some of the pressure pulses. When the spring on the coupler breaks it causes an anoying rattle. Once the supercharger is under a load the noise should stop.

I'm not sure where to buy a new one, maybe Magnum Powers.

David
 
SC Vacuum Line.........CHECK IT!

Check the vacuum line between the inlet plenum and the SC waste gate. I put a new end on my vacuum line when I did my SC upgrade and pushed it on too far which plugged it up. When I started my 90 Super Cougar it sounded like someone threw a hand full of ball bearings in the top of my SC. Since the line was the only thing I changed, I pulled the line back off and tried to blow through it. Sure enough it was plugged up. I repositioned the vacuum line end and it worked fine.

If the vacuum line is cracked, the same thing will happen because the the waste gate is spring loaded to close when no vacuum is applied. It is worth a look before tearing your SC apart.

Ed Springer

edspringer1@aol.com

90 Black Super Cougar 5-speed: 70mm TB, Fresh Air Intake, Upgraded '94 Supercharger, 5% SC Pulley, Raised SC Top, I/C Fan, Underdrive Pulleys, Headers, Magnaflow Muffler (no cats), 3:27 Gears, Ripper Shifter, 73 CL MAF, Magnacore Wires.

94 Red SC Auto: 70mm TB, Fresh Air Intake, Stock 90 SC Pulley, Raised SC Top, I/C Fan, Underdrive Pulleys, Headers, Magnaflow Muffler (no cats), 3:73 Gears, 73 CL MAF, Magnacore Wires, TRANSGO Shift Kit, Haydon Auxiliary Transmission Cooler.
 
Even if it is the coupler, or the gears...

You still have to admit, that when someone "rebuild" something, that usually entail checking all parts for excess wear and checking the tolerances for everything.. If it made this noise prior to "rebuild", then the chances are that they did a poor job doing whatever they did to it. How much did the "rebuild" cost? It doesn't really matter about the cost, if you paid for a "rebuild", then you should expect one for your money!! I would raise hell if I were you!!

Just my 2 cents,

Phil
 
The rebuild was done at Magnum Powers along with the magnaport II. I've called him about the rattle and he did mention it could be worn gears, but when he looked at them during the rebuild, they looked fine. My bet is it's either the coupler or the gears. Now to find them will be the challange!
 
Phil,

A supercharger rebuild doesn't include new gears or the bearings and seals that seperate the gear oil case from the rotors. That part is considered non-serviceable by most rebuilders.

The snout bearings and seals, drive coupler and the needle bearings in the back of the case are all that a typical rebuild covers.

David
 
What I am trying to get at is...

I wasn't sure what the rebuild encompassed, but if you pay big $$ for a rebuild and you still have the same problem afterwards, someone hasn't done there job right!! I know they can't replace the gears, lobes etc. but if there is doubt or if checked and found to be worn, you don't just rebuild the rest of it and send it back to the customer. You should notify the customer first and tell them of the situation.

Phil
 
Okay, now everyone loosen your sc belts and check for play. Let us know if you have play and/or a knock when you turn the pulley. I tried it on my 94 and I have the same situation. I was wondering where that noise was coming from, I always thought it was normal lifter/valve noise or something. I hate to think that this is something I need to replace (is it?) At idle though, when I bring it to 900-1000+ RPMs it goes away. It seems the loudest when I first start it up and when I am on an incline in park.
Does anyone know where to get a new coupler and how hard/expensive is it to replace??

Oh, if this means the gears are worn (hardly likely on mine->newer version sc, 111K miles) does this affect performance/boost? I get good performance I think for being stock and boost is max at 16psi, never comes in too early.
 
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