FAQ: Fragged Tensioner/Idler Pulley Reports & Questions

the new plastic aftermarket pulley have greatly improved bearing designs compared to the OEM ones. I wouldn't hesitate to use one of the upgraded plastic ones now.

Which pulleys have upgraded bearings? Where do we find them?

I replaced a tensioner pulley 2 weeks ago from NAPA and the bearing in it was made in China.
Don't expect it to last that long.

I've had my steel Daycos in for 4 years/80K miles now. No signs of wobbly bearings anywhere.

I'm not positive it's coming from the supercharger but it almost seems to be coming from the pulley area on over, which I guess is the coupler?

Most of what i've read says they rattle when they go bad. Mine isn't rattling but making a whining type noise that increases at higher rpms. It's still there at idle just not as noisy. Is that a possible symptom?

Is the alternator really hot to the touch? It will whine when the bearings are on the way out.

Do they not get pretty hot anyways?

I'll check it when I drive home in a bit. There is 187k on the alternator though and it was hard to tell if the noise was coming from the snout or alternator.

My OEM alternator failed at 35k miles. The replacement (GM) has been fine for 150k miles so far. Before it was repaired, it whined for a couple weeks straight. My mechanic opened the hood, felt the alternator with his hand, told me it was bad, then dealership fixed under warranty.

I just felt it and it was hot, but not hot enough that I couldn't hold my hand on it. It really sounds like it's coming from the supercharger snout and I thought I had noticed it had been making a noise for awhile. It almost sounds like a cracked window with wind whistling through it.

Maybe I'll try holding a broomstick up to the alternator and snout. Is the coupler inside of the snout? I don't know jack about superchargers

yes the coupler is right behind where the snout meets the blower casing.
i have never heard a bad coupler make a whine noise, but i have heard just about everything else make odd noises.
few things come to mind to check:
power steering pump got fluid in it?
did you rock the s/c pulley to see if there is play in the coupler?
have you taken the s/c belt off to see if you could isolate the noise?
all the idlers feel good?

Well on my way home just a few minutes ago the belt apparently let loose or shredded. Battery light came on, temp got higher, and power steering was gone.

This couldn't have come at a worse time, luckily I was close enough to limp it home. I don't really think it's the alternator though. The pulley spins freely as well. Hmmmmmmmmm!

But it didn't break. I was wrong before and I don't believe it has anything to do with the SC.

When I spin the alternator pulley by hand it spins freely but it does squeak. Not super loud. I wonder though why the belt would have popped off and not broke, because I thought the pulley would have seized? If it hadn't seized and is only squeaking, is that likely the cause or no?

So it's not the alternator. I was looking at pictures and noticed a pulley I didn't see earlier.

The accessory tensioner pulley froze. The plastic pulley part came apart from the metal part and popped off. It was laying under my axle.



The #1 pulley is the culprit.

I just took off the metal part that remained and the last few bearings fell out into my hands. It was trashed!

If your local auto parts store carry's Dayco the P/N is 89007 for the tensioner pulley. #1 and #2 in this picture are the same P/N, may as well replace both.
And when you feel ambitious replace #4, hidden behind the engine mount, It is P/N 89006. There is a write up on here about replacing that and all the pulleys.
I just did all my Pully's last weekend as I was hearing one going bad. When one goes bad the rest are soon to follow as they all have the same amount of hours / mileage on them.
Took me about 3 hours to do all of them. I took a few breaks for my aching back.
Good luck and happy wrenching.

Thanks Rickw. Gonna go pick up new pulleys and belts. I won't be doing #4 until it self destructs lol. Now that I think about it, this pulley may have been making a minor noise for quiet awhile and suddenly got worse and then came apart.

That's how they fail. They make a little noise for a short period of time and then they let go.
I would seriously consider planning some time in the near future and doing the one that is hidden behind the mount. The noise I was hearing was from one of the easy ones to replace, but once I got the belt off and felt for play in all the other pulleys, I found that #4 was loose also. That's the one that takes all the labor to replace. If it fails while your on the road your screwed.
What year is your car? As you might have to loosen the mount just to replace belts, at that point a little more labor and you can have the mount off and replace everything for preventive maintenance and peace of mind. I am glad I broke my back doing all of them.
The pullyes aren't that expensive, hell the belts cost more than the pulleys combined.

Also: P/N's for Dayco Poly Cog Belts (Look like Gatorbacks)

Accessory Belt = # 5060940
Supercharger Belt = # 5060720

Note: These are P/N's for my 1998, don't know what else they fit.

Yea this one failed on the road but luckily I was a mile and a half from home.

Car is a 97. Picked up gatorback belts and duralast pulleys. They are metal and pretty heavy compared to the original plastic pulley.

Yea, That's what the Dayco P/N's I gave you (Metal Pulleys)
I didn't know you already bought the parts.
Good Luck. For changing the belts, if you haven't already done a 3800 L67 before, there is a write up in here that was helpful to me. Gave me few pointers on some things that weren't so obvious. Otherwise it is a straight forward hairball.

How many miles on your 97? Do you know if the pulleys are original? When I lost my SC tensioner a year ago, all the pulleys looked half decent but probably original OEM plastic. Until I looked closer at the bastard pulley behind the engine mount. It was so worn out, the plastic surface that the belt runs against was darn near worn all the way thru. It was OBVIOUSLY original and had to be replaced. Examine yours closely, you really don't want to have to mess with it soon after doing all the others and belts. It's worth getting it over with.

187k on the clock and yes I'm positive it was the original. I'll definitely check that last one when I get to it, hopefully tomorrow.

Still trying to picture how to get these belts off and on lol. I guess the best way would be to remove the wheel and splash shields?

no need to take off the wheel or shields. most of the work is done from the top. you will have to raise and lower the engine, pull out the bracket's lower bolt, and get under there to loosen the 2 bolts on the bottom of the mount support.

https://rivperformance.editboard.com/Supercharged-3800-Tech-c2/Series-II-Engine-Transmission-f4/Write-Up-Replacing-Belts-and-Pulleys-t725.htm

look at this write-up

wonderful......s/c belt just shrapnelled under my hood......now I got to deal with the frickin belt job........shoot me now......

Replace them both, then don't worry about it for 80-100k miles.