SNOWBIRD

Recently I have noticed a noise in the back that has definately got louder, sounds like a shroud is loose or the exhaust is rattling BUT It seems to come on at around 1,000rpm gets louder and then goes away when it hits around 2,000rpm... Seems like whatever it is, it's loose until the engine winds up and goes away instantly... Very hard to describe noises...

C4Russ

It's not going away if it's the alternator bearings, it is simply being masked by the other wonderful noises of an air/oil cooled flat six Porsche engine.

If the noise is somewhat ringing or shimmering, I'd bet it is the alternator pully bearings rather then the alterator itself. If so, when it falis, it'll likely take the belt with it. Best to get it fixed straight away. It's a fairly easy DIY.

garrett376

Often when the belts are old (alternator and fan), or when they're not tensioned correctly, a screechy, oscillating sound will occur especially at idle, and when cold. Anyhow, for me it was a new set of belts that got rid of the problem!

SNOWBIRD

"the noise is somewhat ringing or shimmering"
The ringing or shimmering is a pretty good description. Starts out sounding like somethings loose, then gets louder (pretty loud) then stops at like 2,000rpm.

I guess it wouldn't hurt to remove the belts and start it for a second to see if it goes away.... Anybody see a problem with that? Is that a good way to diagnose it?

jimq

Mine does it sometimes also. It seems to be coming from a heat shield near the Cat converter. See if any of your tin work is lose or vibrating.

viperbob

Another very common problem that will give you a similar noise is the belt sensor roller. These go bad and make a terrible noise.

Indycam

"I guess it wouldn't hurt to remove the belts and start it for a second to see if it goes away.... Anybody see a problem with that? Is that a good way to diagnose it?"
I would be far better to go to the car parts store and pick up a can of belt dressing in a spray can .
You spray it on one belt while the motor is running , if it " fixes " the noise you have found the problem . If the noise does not change , spray the other belt .
The spray on belt dressing is not a fix in and of itself , its just a way to find what belt is the problem belt . If the belt dressing stops the noise and you do not fix the belt by putting more tension on it or replacing the belt or doing whatever it needs to really fix it , the noise will be back soon .

If you do try the spray on dressing , hold a bit of card board
behind the belt so that the spray that doesn't hit the belt will
land on the card board . No need to have a big globe of gluey stuff stuck to your tin work .

Going to the trouble of removing the belts and pulleys is good fun if you like that sort of thing .

MarkD

You can check the rear alternator bearing like this:
1. Remove Alternator belt (outer belt).
2. Spin alternator shaft and watch the fan.
3. If the fan wobbles within the shroud the rear alt. bearing is bad or going to be.


The noise you describe sounds like it is possible the fan is contacting the shroud? Look for marks in the shroud. The clearances are tight there!

Good luck!

SNOWBIRD

I checked, there are marks (rub marks from blade) around the top. I reved it and coudn't see it make contact, but the vibration I felt on the shroud tells me that the problem is there somewhere rather than a lose exhaust.

Looks like 1/2 the work is getting the belts off, is that accurate? Thinking of D.Y.I'n it. Looks like $360+/- for the bearing and a new alternator. Anybody know what reasonable install time would be for both? The female torx is buttered up pretty good, thinkinking it'd be a good time to replace the alternator.

SNOWBIRD

Follow up... Was the fan bearing. Had a new one installed today, problem solved.

jimq

Did you have just the bearing replaced or the whole alternator? About what was the cost. I have also seen a slight grove in my shroud before but cant tell how long ago it happened orif it was replaced before I bought it.

MarkD

Sorry for the late reply. For others or future reference:

I replaced mine proactively (was wobbling, not contacting) and found a Bosch reman. (Bosch lable on the box) alternator for $152 with exchange @ egermanparts.com (no affil.). Best deal I found.

SNOWBIRD

No Jim, I didn't do the alternator,mechanic talked me out of it, "should be good for 100k + the end wasn't battered too bad" yadda yadda yadda. Total was $469 w/tax - $137 part, $300 labor, he said the bearing was a bugger to get off. Note, I didn't bring my book down, and only have some of my tools here in FL. BTW, This is a different shop than the one that did the 60k service, mechanic mentioned the drive belt was very tight and thought it could have been a contributing factor to it going bad. I really feel..... violated by this outfit! $2400 for the service, $700 of it for a distributor I don't believe I needed and it still doesn't run as good as it did when I brought it in!

jimq

If it aint broke dont fix it
Every time I fix something before it breaks something else will break soon after.