1998 Audi A4 Avant Quatro - 175,000
ECS ultimate plus timing belt kit at 140 k
regular oil changes
CEL is on, last time scanned it was miss firing, what a surprise
new plug wires, and ignition control module (coil packs)
About to do all the vacuum lines cause as you can see they look like everyone else's TOAST

Sounds similar to the power steering pump going. All the fluids are straight. No supercharger here.
I have been researching the past few days and it sounds like tensioner pulley on the serpentine belt??
The car idles and runs "fine". Ill have to take the bumper, radiator and all that to do the tensioner pulley?

I read that I can loosen the pulley take the belt "off" start the car for a 30 seconds, to see if the sound is gone. Im hopping its nothing internal. What does it sounds like when your main bearings go?

Help, i love these cars, This has been like this for a year. Its not my DD. But I start this car every week at least. I walk by it a lot and want to DRIVE IT.

 

I did my tensioner on my 2.8 without removing the bumper. Took me about an hour or so. Should have been shorter

 

any suggestions before getting my hands dirty? I dont like throwing parts at cars. Anyway to be sure its the tension pulley?

 

There's not a lot of space in there to access the serpentine tensioner pulley, but one trick is to remove the electric radiator fan. To remove the fan, you have to break off a plastic tab and undo one screw. For the life of me I couldn't figure out how to get that fan out until I read about breaking off the tab.

Removing the fan gives you an extra 2"-3" of space to get at the tensioner. Once you get the belt off, you'll be able to spin the pulley and determine if the bearings are shot. I think you'll want to keep tension on the pulley.

The bearings on my tensioner went at 140k miles and then the thing exploded on me. No damage done, but I was lucky to be 300 yds from home and was able to drive without power steering needed

 

A little update and reaching for advice:
I got the serpentine belt off to narrow down this nasty sound. To my luck the sound was gone!!!!! So Im hoping its the tensioner pulley. I check all of the pulleys for wiggle and dry bearings. The tensioner pulley doesn't seem to wiggle and spins decent, Will i be able to tell if thats the cause of the noise. Also the power steering pulley, (right under your coil packs) wiggles a bit and I feel something catching as you spin it about a quarter way. If I spin these pulley shouldn't i be able to hear something if its blown?

 

anybody that has done a tensioner pulley: How did the bearing feel when you took it off? Was it noticeable that the noise was coming from there?

 

When I removed mine, it turned just fine when I was turning it by hand. Didn't feel friction or hear it squeal. So I just assumed it was bad and the sound would only happen at high rpms(high meaning faster than I could turn by hand).

I say the odds are on your side and it is the tensioner pulley.

 

that sounds a lot like how my car sounded when my alternator bearings blew.. its hard to tell though.. cause there's a lot of force on from the belt so turning it by hand might feel fine but when the friction is there its another story. i knew it was the alt cause i could see smoke coming off of it lol

 

So I replaced the tensioner pulley.. First off THANK YOU redmond1501!! I was trying to remove that fan then i remembered you mentioned something about breaking, I would have never figured that out!
Here are some pictures where you break the clip off and with the new pulley in.

The noise was still there! Booooo! So anybody got any ideas, im going with the power steering pump.. The pump seems good, as in it doesn't growl when you steer. Can i just replace the bearing and pulley instead of the whole pump for 200.
The alternator is suspect as well. Has anyone installed new bearings in the alt or just bite it and buy new?

Also in the 1 picture I highlighted a small black box in red thats on the ignition module. Mine is damaged and i had to solder it back on. What is this parts purpose?