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#3307601 - 03/10/14 08:10 PM 1,900 RPM rattle diagnosis help
NMBurb02 Offline


Registered: 09/12/12
Posts: 1981
Loc: Greatest Earth on Show, UT
The GP (supercharged GM 3800) has developed a strange rattle/scraping sound. It comes from the passenger side of the engine compartment and sounds sort of like a loose heat shield vibrating against a piece of metal or metal blades scraping against metal. It only happens at 1,900 rpm under light/medium load, such as when slowly accelerating or going up a slight incline, and seems to happen more often when the engine is fully warm than when cold. The noise stops if you raise the rpm to 2,000 or drop to 1,800 and does not happen if you just run up through the rpm quickly. It can't be reproduced for any length of time when parked because it needs that load; I can be parked and hold the engine at 1,900 rpm with no unusual noise. And it is not speed/gear dependent: it happens at 35 mph on city streets or 65 mph on the highway. Also not dependent on A/C or heater operation as it happens with it both on and off.

I have checked for loose heat shields and cannot find any.

Any idea what it could be? I'm at a loss and will take it into a shop for diagnosis later this week if nobody here can help me nail it down.
_________________________
2002 Chevy Suburban 1500, Rotella T6 5W-40, Fram TG3675
2006 Pontiac Grand Prix GT, G-Oil Syn 5W-30, Fram TG3387A

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#3307604 - 03/10/14 08:13 PM Re: 1,900 RPM rattle diagnosis help [Re: NMBurb02]
spasm3 Offline


Registered: 05/30/10
Posts: 8652
Loc: North Carolina
Could it be a belt tensioner failing?
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#3307615 - 03/10/14 08:22 PM Re: 1,900 RPM rattle diagnosis help [Re: spasm3]
cknight49090 Offline


Registered: 01/25/14
Posts: 275
Loc: south haven mi
Its the supercharger coupler you have to pull the blower nose to replace it. its a 20.00 part and you have to replace the oil in the supercharger at the same time.Search for the noise on utube and look on ebay for the parts to fix or zzp.


Edited by cknight49090 (03/10/14 08:23 PM)

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#3307674 - 03/10/14 08:53 PM Re: 1,900 RPM rattle diagnosis help [Re: cknight49090]
ls1mike Offline


Registered: 06/14/08
Posts: 5118
Loc: In the Garage...
Originally Posted By: cknight49090
Its the supercharger coupler you have to pull the blower nose to replace it. its a 20.00 part and you have to replace the oil in the supercharger at the same time.Search for the noise on utube and look on ebay for the parts to fix or zzp.

This!
Easy Fix. It is plastic. I guess it is in case something locks up, that way you don't break everything. The get loose as they age.
stock coupler
aftermarket coupler
_________________________
Mike
00 Trans Am WS6 5.7 LS1
02 Silverado 2500HD 6.0
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15 Malibu LTZ Turbo
12 Passport TT

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#3307698 - 03/10/14 09:23 PM Re: 1,900 RPM rattle diagnosis help [Re: ls1mike]
NMBurb02 Offline


Registered: 09/12/12
Posts: 1981
Loc: Greatest Earth on Show, UT
Originally Posted By: ls1mike
Originally Posted By: cknight49090
Its the supercharger coupler you have to pull the blower nose to replace it. its a 20.00 part and you have to replace the oil in the supercharger at the same time.Search for the noise on utube and look on ebay for the parts to fix or zzp.

This!
Easy Fix. It is plastic. I guess it is in case something locks up, that way you don't break everything. The get loose as they age.
stock coupler
aftermarket coupler

Those links say that the coupler noise is only at idle. Mine is only at 1,900 rpm.
_________________________
2002 Chevy Suburban 1500, Rotella T6 5W-40, Fram TG3675
2006 Pontiac Grand Prix GT, G-Oil Syn 5W-30, Fram TG3387A

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#3307713 - 03/10/14 09:35 PM Re: 1,900 RPM rattle diagnosis help [Re: NMBurb02]
ls1mike Offline


Registered: 06/14/08
Posts: 5118
Loc: In the Garage...
Right, this is my third supercharged 3800. When the coupler goes you will hear it above idle. It will do it a weird times depending on load and engine temp.
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Mike
00 Trans Am WS6 5.7 LS1
02 Silverado 2500HD 6.0
14 Caprice PPV 6.0
15 Malibu LTZ Turbo
12 Passport TT

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#3307715 - 03/10/14 09:37 PM Re: 1,900 RPM rattle diagnosis help [Re: ls1mike]
NMBurb02 Offline


Registered: 09/12/12
Posts: 1981
Loc: Greatest Earth on Show, UT
Originally Posted By: ls1mike
Right, this is my third supercharged 3800. When the coupler goes you will hear it above idle. It will do it a weird times depending on load and engine temp.

Cool. It's a cheap fix, so I guess I don't have much to lose. Is the aftermarket coupler worth the extra price? I run a stock pulley and don't plan on going smaller.
_________________________
2002 Chevy Suburban 1500, Rotella T6 5W-40, Fram TG3675
2006 Pontiac Grand Prix GT, G-Oil Syn 5W-30, Fram TG3387A

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#3307726 - 03/10/14 09:44 PM Re: 1,900 RPM rattle diagnosis help [Re: NMBurb02]
ls1mike Offline


Registered: 06/14/08
Posts: 5118
Loc: In the Garage...
I run the stock one with mods.
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Mike
00 Trans Am WS6 5.7 LS1
02 Silverado 2500HD 6.0
14 Caprice PPV 6.0
15 Malibu LTZ Turbo
12 Passport TT

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#3307733 - 03/10/14 09:49 PM Re: 1,900 RPM rattle diagnosis help [Re: NMBurb02]
cknight49090 Offline


Registered: 01/25/14
Posts: 275
Loc: south haven mi
I used it in mine buts its modded.For 10 more bucks its peace of mind at the least.I got the coupler and oil from zzp if you get it from GM you need two bottles, they ZZP) have it measured out already.There are kits on ebay as well.

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#3307772 - 03/10/14 10:17 PM Re: 1,900 RPM rattle diagnosis help [Re: NMBurb02]
NMBurb02 Offline


Registered: 09/12/12
Posts: 1981
Loc: Greatest Earth on Show, UT
Thanks for the info. What is a rough time estimate for replacing the coupler? Are any specialty tools needed?
_________________________
2002 Chevy Suburban 1500, Rotella T6 5W-40, Fram TG3675
2006 Pontiac Grand Prix GT, G-Oil Syn 5W-30, Fram TG3387A

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#3307803 - 03/10/14 10:51 PM Re: 1,900 RPM rattle diagnosis help [Re: NMBurb02]
cknight49090 Offline


Registered: 01/25/14
Posts: 275
Loc: south haven mi
An hr for a tech. No nothing special, getting the old oil out is the hardest part.And you have to use a non hardening gasket maker on the nose at least that's what they recommend.

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#3307809 - 03/10/14 10:57 PM Re: 1,900 RPM rattle diagnosis help [Re: cknight49090]
cknight49090 Offline


Registered: 01/25/14
Posts: 275
Loc: south haven mi

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#3318904 - 03/21/14 10:45 AM Re: 1,900 RPM rattle diagnosis help [Re: NMBurb02]
NMBurb02 Offline


Registered: 09/12/12
Posts: 1981
Loc: Greatest Earth on Show, UT
Well, it's not the supercharger coupler!

It started off pretty doubtful as there was no back-forth wiggle in the pulley. I pulled the nose cone off last night and the old coupler was in great shape with no hole disfiguration. In fact, it was on there pretty snug and I had to pry it off to put the new one on (I had already purchased and received it, so why not?). I was not able to get a good test drive in last night to get everything up to temp, but this morning I have confirmed that the noise is still there.

Could this be a bad water pump? The pulley seems to have a bit of wobble while the engine is idling but I did not try moving it by hand while I had the belts off. The current unit is a Bosch that has been on there for about 9 months and 10,000 miles (still within the shop 12 month/12,000 mile warranty!).

Whatever it is, I will be taking it in for diagnosis on Wednesday (shop is booked today, closed on weekends, and I will be out of town from Sunday afternoon through Tuesday evening) and will update this thread when I know more.
_________________________
2002 Chevy Suburban 1500, Rotella T6 5W-40, Fram TG3675
2006 Pontiac Grand Prix GT, G-Oil Syn 5W-30, Fram TG3387A

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#3322035 - 03/24/14 01:06 PM Re: 1,900 RPM rattle diagnosis help [Re: NMBurb02]
Brent_G Offline


Registered: 07/12/11
Posts: 456
Loc: Aberdeen SD
Look forward to hearing what they find on this, mine is doing the same identical thing.
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05 Grand Prix GTP
01 Ford F150
06 Yamaha R1
69 Roadrunner 528 Hemi
68 Dart GTS 512
71 Superbee's 440 and 383
87 Camaro 540 BBC

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#3325393 - 03/27/14 01:40 PM Re: 1,900 RPM rattle diagnosis help [Re: NMBurb02]
NMBurb02 Offline


Registered: 09/12/12
Posts: 1981
Loc: Greatest Earth on Show, UT
The shop says it is an internal issue with the catalytic converter (breaking up?) and the resonator(something loose, maybe a piece of the cat?). I think there has been something loose in the resonator since I first bought it or shortly thereafter, but the cat issue is new.

I will continue to drive it as-is, but it sounds like a good excuse for a full aftermarket exhaust system!
_________________________
2002 Chevy Suburban 1500, Rotella T6 5W-40, Fram TG3675
2006 Pontiac Grand Prix GT, G-Oil Syn 5W-30, Fram TG3387A

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