Belt replacement noise

[botchup]

Hi Guys,

I've replaced the alternator/AC belt on my car with a gator-back belt which is supposed to be quieter, the belt is different in that it has striations that run length ways (like a normal belt) but also that run across the belt. Anyone else had issues with this type of belt?

After fitting the belt it was anything but quite, there is a continual screeching coming from the front of the engine, I tried tightening the belt and the power steering belt - in-case its that was making the noise, its rather difficult to tell exactly where the noise is coming from, it made no difference.

I'm worried that the noise is not the belt at all but a bearing on either the engine, AC compressor, or Alternator. Is it possible that this kind of problem would show up with a simple belt change?

I did check that the AC compressor clutch is dissengated so the pulley is moving (my airconditioner unit does not work).

I've been told that rubbing a dry bar of soap on a belt should remove any belt screech? How true is this?

If I take the belt off and run the engine and the noise goes away - how can I be sure its the belt - surely a bearing will make the noise only when its under some sort of load anyway?

Any advice would be appreciated

[rudidelange]

Old belts can start screeching, especially if they are loose and become glazed. An alternator bearing can also make a noise when the bearing goes or is in the process of going.
Soap can do this temporarily bith an old belt. Some moisture can also silence screeching belts for a short while.
The belt can be screeching if it is too thick / too thin, causing it not to fit properly in the pulleys.
I will anyway check the bearing of the alternator - easy and cheap to replace.

[botchup]

Hi Just an update for anyone who reads this post in the future.

After replacing the gator back belt I mentioned with a standard type belt, only to still hear the noise, I managed to take the belt covers off after removing both the belts, and inspect the inside of the cover, turns out the screeching may be coming from the main pulley on the plastic outer cover... I found that buy tightining the inside part of the cover to the engine helped reduce the noise.

The noise is still somewhat present but only when the belt is on the pulley, that is when the pulley is under load. Cant quite find the exact source of the noise, gonna get the experts to look early next week.

I have also found the my lower balance shaft oil seal is leaking quite heavily now and in the source of my oil leak. I have the seals and will be getting it replaced.

happy motoring!

[rudidelange]

I dont know if the later 944 have the same layout as the earlier ones but I doubt if the screeching noice is from the main crankshaft pulley on the engine. If there are two belts, one for the aircon, and one for the alternator, remove one at a time and see what happens to the noise.

The aircon compressor will only engage is there is sufficient gas in the system. I would still take a bet that it could be the alternator bearing.
Place a long screwdriver or even better a stethoschope on the alternator and the aircon compressor whilst the car is running with the belts on and you will hear if it is the bearings/s. You must of course place the end of the screwdriver to your ear.
All the best

[adrian jaye]

if the belt is too tight you will get squeel

[botchup]

Rudi, I've already checked then air-compressor, alternator and power-steering pump individually and it is definitely none of those components making the noise.

Adrian, I've always been told that its usually a loose belt the will slip and make a noise, in fact I had the belt loose and the noise disappeared but then belt would slip. If I tighten the belt to specification (that is being able to twist it 90 degrees when tight) then I get the noise. I put dry soap on the belt and it makes no difference. I even resorted to tightening and loosening the belt while the car is running - the pitch of the screech doesn't really change, without going too loose. (I am doing this on my back as the car is only on 2 jack stands)

I'm pretty sure its not the belt....

Lets hear what my Mech has to say next week.
Thanks for the input guys.

[rudidelange]

Botchup, Thanks, I am self curious what this could be. will be watching this space
Hope you get it fixed asap

[adrian jaye]

Originally posted by botchup
Adrian, I've always been told that its usually a loose belt the will slip and make a noise, in fact I had the belt loose and the noise disappeared but then belt would slip. If I tighten the belt to specification (that is being able to twist it 90 degrees when tight) then I get the noise. I put dry soap on the belt and it makes no difference. I even resorted to tightening and loosening the belt while the car is running - the pitch of the screech doesn't really change, without going too loose. (I am doing this on my back as the car is only on 2 jack stands)

Sorry I mis-read this,

camshaft belts if they are too tight will squeel,

your AC belts etc squeel if too loose

ooooooooooooooops

[botchup]

Hi Chaps,

You'll never guess what the noise was. Turns out the S2's main pulley is two part. It has an inner metal part thats connected to the crankshaft (outer diameter) and an outer metal part that the belt runs on. there is a rubber damper between the two - the value I'm not all that sure, of. But the outer part was partially slipping on the inner part as the rubber damper has become hard smooth and brittle and is cracking away. Like a slipping belt becomes over time. That was the cause of my noise the whole time.

I was originally told that a new pulley would cost about $121 turns out that was the solid 1 piece 944 pulley, now I'm told the 944S2 pulley like the one thats disentegrated on me costs $538.

Surely this isn't nessasary - couldn't I just use the solid one piece?

Any thoughts on this would be appreciated.

[Makis]

I had a look on my S2 last time I had to fix a problem with the pulley and my one looks like it is the standard one piece item. So I suspect you can replace your one with the one piece item. The problem I had was that the pulley is bolted on to the balance belt crank pulley with 4 bolts. I had twice had the bolts shredded, causing the alternator belt crank pulley to come loose. It may be that this is the reason Porsche went to the extreme and made a two piece pulley to stop it from causing such problems. Replacing the pulley will require to refit the balance belt correctly.

[botchup]

I phoned up my mech who said that he would definitely not put on the one piece as Porsche would have a good reason for making it that way, maybe Makis is right and bolts shredding is it.

So looks like I'll have to pay up. At least the engine will sound nice and quite.. "Porsche engine quite" - ja right!

PS I'm selling my car check out my ad on this site.
click here