Engine whine?

[Nathans_Dad]

I'm trying to figure out where this mysterious engine whine is coming from in my 1984 coupe. It is a high pitched whine that comes on around 2000 rpm, increases in pitch until about 3-4k rpm and then goes away. If you hold the RPMs there, no more whine. If you decelerate slightly the whine is there but quieter. If you then accelerate again, it will come back. Does not happen at idle. If you rev the engine quickly in neutral, I think you can hear it but it lasts only a moment so it's hard to tell. I changed out the belts on the car today thinking maybe it was a old/loose belt, no improvement.

With my head inside the engine bay and the car running, I think I can hear it coming from somewhere near the air cleaner but I can't be sure. I wish there was a way for my to put it on a dyno or something and try to localize the sound but I don't have access to one.

Any ideas?

[Rot 911]

Sure it is not the noise you hear from the fan on the Carrera 3.2 engine. It has a very distinctive whine that I have not heard on any other 911 engine. Almost sounds like a turbine.

[Nathans_Dad]

I had an 84 targa and it did not make this sound. It really sounded almost like a belt slipping which is why I changed out the belts. It's that kind of high pitched whine/squeal.

[Mattcamp]

alt bearings?

[Nathans_Dad]

That's a thought, is there a way to isolate the alternator and take the car for a short drive to see if the sound goes away?

[Nathans_Dad]

Here's another question, when I took the pulley off, there were only 4 shims, all on the inside. Luckily I had picked up some extra shims just in case. It seems I can only get the belt reasonably tight with two shims on the inside and four on the outside but the belt still seems to have a bit too much play in it as I watch the engine idle.

I got the belt at O'Reilly's and they said it was correct for my car and year. I read about people having 5 shims on the inside and being tight, is the belt the wrong size?

[steve911T]

Nathan's Dad, had a whine between 2000-3000. I am assuming you can hear the whine when the decklid is up. Removed fan belt from the alternator, started it up quickly for 30 seconds and whine was still there. Then put the belt back on, removed belt to AC compressor and started and whine was still there. Turned out to be chain tensioner. It is an easy way to isolate the most common problems. I am not sure I would drive it long without the fan belt/alternator functioning. Steve

[ossiblue]

You asked for some thoughts. Since you heard the whine when your head was in the engine compartment, I'd suggest you try Steve's idea and remove the belt to eliminate it (or the alternator) as a cause. The short duration it would be off should cause no harm. If the noise is still there, let us know.

As far as the new belt, what is the make and size? Belts that cross reference in auto parts books often don't fit too well and it sounds like yours may be a bit large. There was a recent thread about this where a Goodyear belt was involved, but it was too small rather than too large as in your case.

BTW, your post about the high pitched whine/squeal makes me think alternator bearings too.

Another WAG. I don't know about later cars like yours but I have read about frequency valves (my CIS doesn't have one). I know they are supposed to vibrate. Could the sound possibly be related to the frequency valve--assuming you have one on your system?

[Nathans_Dad]

Well it isn't the K&N air cleaner either. I swapped it out for the stock cleaner, no change.

Btw, what the hell was Porsche thinking putting those airbox clips at the back of that cleaner? You have to be Plastic Man to get your fingers back to the lower rear clip!

[86 911 Targa]

Originally Posted by ossiblue

You asked for some thoughts. Since you heard the whine when your head was in the engine compartment, I'd suggest you try Steve's idea and remove the belt to eliminate it (or the alternator) as a cause. The short duration it would be off should cause no harm. If the noise is still there, let us know.

As far as the new belt, what is the make and size? Belts that cross reference in auto parts books often don't fit too well and it sounds like yours may be a bit large. There was a recent thread about this where a Goodyear belt was involved, but it was too small rather than too large as in your case.

BTW, your post about the high pitched whine/squeal makes me think alternator bearings too.

Another WAG. I don't know about later cars like yours but I have read about frequency valves (my CIS doesn't have one). I know they are supposed to vibrate. Could the sound possibly be related to the frequency valve--assuming you have one on your system?

Belt sizes can be ambiguous at best.

Here is what we have on our '86 3.2:

1. Fan belt P/N 999 192 176 50 9.5 X 710 mm

2. Three shims between the pulley halves, and
three inside the cup.

Good luck,

Gerry

[Nathans_Dad]

Replaced the O'Reilly's fan belt with one from my local Porsche mechanic, a Continental belt. The Continental belt was a touch smaller than the Gates belt but not by much. I was able to get it acceptable with 3 shims on either side of the pulley. Took it for a test without the A/C belt on and...

Still whining.

I guess I could pull the alternator and see if that is it, the fan spins freely and quietly without the belts on it though, if the alternator bearings were gone, it should be noisy, right?

I'm beginning to go back to idea that it might be my R&P bearing. Hope not.

[ossiblue]

Originally Posted by Nathans_Dad

Replaced the O'Reilly's fan belt with one from my local Porsche mechanic, a Continental belt. The Continental belt was a touch smaller than the Gates belt but not by much. I was able to get it acceptable with 3 shims on either side of the pulley. Took it for a test without the A/C belt on and...

Still whining.

I guess I could pull the alternator and see if that is it, the fan spins freely and quietly without the belts on it though, if the alternator bearings were gone, it should be noisy, right?

I'm beginning to go back to idea that it might be my R&P bearing. Hope not.

If the belt is off, there is no tension on the bearings and there may not be any noise.

As far as the R&P bearing, I had that failure and it didn't have the symptom you describe. Rather, it was a definite whine/grind under load and typically in certain gears rather than rpm, though it was more noticeable at certain speeds/rpms. It got progressively worse, and a slight vibration became noticeable in the shift lever. Your description, which included the word "squeal" doesn't match the sound I heard. You also said you heard the noise while revving the engine with your head back there--likely not R&P but it's still a possibility.

If it were me, I'd at least eliminate the alternator by removing the belt and running the car,very briefly, through the rpm range or removing the alternator an having it checked out.

[Nathans_Dad]

My concern with that is that I would have to drive the car for about 3 minutes or so (around the block) in order to check it under load. It really doesn't make any abnormal noise at idle. I don't want to overheat to engine, would it be ok?

[ossiblue]

Originally Posted by Nathans_Dad

My concern with that is that I would have to drive the car for about 3 minutes or so (around the block) in order to check it under load. It really doesn't make any abnormal noise at idle. I don't want to overheat to engine, would it be ok?

I was under the impression you could hear the noise while revving the engine by hand. I certainly don't have enough knowledge to recommend to someone else to drive for 3 minutes without the fan spinning/alternator charging. If it was my car, and the noise could consistently be caused at a specific rev or easily replicated condition, I would probably try it as I would be able to do it within a matter of seconds of starting. If the car has to be warmed up and running under load (ie. actual driving) to duplicate the noise, then I'd probably remove the alternator for testing.

[Nathans_Dad]

Well, let me try to clarify. On my previous test drives after changing belts/ac/etc, I can get it to make the noise consistently in 2nd gear. To get into 2nd, I have to get to the end of my street (1/2 block) and the turn into the next street and accelerate. I can get into the rpm range in 2nd about one block down that street. At that point I could turn around and head back.

[Nathans_Dad]

As far as making the noise when it revs, I THINK it is making the same noise but it's hard to tell exactly because the noise is very brief when revving and gets lost in the rest of the rev/whistle that is normal for the engine when revving without a load. So, I'm not sure I would be able to tell for certain just by revving it. Does that make any sense?

[ossiblue]

Originally Posted by Nathans_Dad

Well, let me try to clarify. On my previous test drives after changing belts/ac/etc, I can get it to make the noise consistently in 2nd gear. To get into 2nd, I have to get to the end of my street (1/2 block) and the turn into the next street and accelerate. I can get into the rpm range in 2nd about one block down that street. At that point I could turn around and head back.

If you can duplicate the noise as described, even when the engine is first running and very cool, then you might try it without the belt. However, just to be safe, you could take your belt along and once you've gone the block and 1/2, stop and replace the belt for the ride home. From what you posted, I don't think you will risk overheating during such a short run.

[Drisump]

Originally Posted by Nathans_Dad

Well it isn't the K&N air cleaner either. I swapped it out for the stock cleaner, no change.

Btw, what the hell was Porsche thinking putting those airbox clips at the back of that cleaner? You have to be Plastic Man to get your fingers back to the lower rear clip!

Frigging impossible....sorry you have to do an engine drop to do the last one up....LOL

[hcoles]

I may have missed it.... was the belt removed and car rev'ed/driven?
You can tell belt tension/slipping by looking at where the belt is riding and pushing on it to get a sense of the tension.
Running for 3 minutes at low throttle settings, I'm not guessing that would over heat anything.

[Gogar]

+1 that you should take off the ALT belt and the AC belt for a short time when the engine is fairly cold and drive around the block once or twice max.