924Board.org

RobertN · Joined: 19 Apr 2015 Posts: 142 Location: Lisburn Co Antrim

Hi guys, start up car and as soon as I Rev slightly she squeals continually. If I Rev hard it diminishes and once back into idle the stealing starts. I have tightened the alt belt as it was loose a while back and gave the usual high pitch sound as slipping. Tension at 9.5 mm approx! It's not that type of high pitch this time. I happened to feel the tension pulley below cam belt cover and i can turn it quite easily, could that be the problem. Btw Ac is off during this!
Thanks.
_________________
Robert.
Porsche 924 N/A 1984.
Electrical Engineering Sales to Control panel builders.

leadfoot · Posted: Thu May 28, 2015 9:15 am Post subject:

slacken the alt belt off temporarily and eliminate this as the issue, might need a new belt if the noise goes away, cam tensioners are fairly cheap and are sealed bearings iirc, so pretty much replace if in doubt...
_________________
1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

RobertN · Joined: 19 Apr 2015 Posts: 142 Location: Lisburn Co Antrim

thanks mate. Should I just remove the alt belt off all pulleys and start the car for a few seconds just to see?? I did get "slack alt belt" noise a few weeks ago, and measured the tension and it was about 25 mm!! and should be 9.5mm so I replaced the belt and tightened to spec and it was okay, but this noise has always been there since I got the car 8 weeks ago.
_________________
Robert.
Porsche 924 N/A 1984.
Electrical Engineering Sales to Control panel builders.

leadfoot · Posted: Thu May 28, 2015 8:53 pm Post subject:

The car relies somewhat on the alt for starter load, depending on the health of your battery it may start ok, just remember it also drives your water pump too...
How old is the belt?
_________________
1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

RobertN · Joined: 19 Apr 2015 Posts: 142 Location: Lisburn Co Antrim

okay I'll remember that. im not sure how old the belt is as it was in car as a spare. I fitted it about 6 weeks ago and the squealing noise from alt stopped. this sound is a continuous pitch on idle and as you rev hard it doesn't increase as a slipping alt belt would.. I'll try your suggestion after work tonight to illuminate the alt belt and alt bearing possible problem??
_________________
Robert.
Porsche 924 N/A 1984.
Electrical Engineering Sales to Control panel builders.

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

The other thing that can cause belt squealing is a failing lower alternator mount bushing. It is a large "bonder rubber bushing" (to use the parlance from PET) that takes tons of abuse from leaked oil and heat fatigue due to the exhaust manifold. When the bushing begins to fail and you further tension the alternator, it will cause the alt to be pulled at an angle askew of the water pump and crank pulleys. This misalignment can cause accelerated belt wear, bearing failure in the alternator itself, and possibly additional stress on the water pump bearings. I would take a good hard look at the alternator to see if its pulley is properly aligned.
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erstwhile owner of just about every 924 variant ever made

RobertN · Joined: 19 Apr 2015 Posts: 142 Location: Lisburn Co Antrim

Cheers for that. I have had the alternator refurbished, ie voltage regulator & rectifier by auto spark at the same time I had the starter motor brushes and cables done. ( see post "Starter motor wires fried" )
ill check the alignment and bushes.
_________________
Robert.
Porsche 924 N/A 1984.
Electrical Engineering Sales to Control panel builders.

leadfoot · Posted: Fri May 29, 2015 9:58 am Post subject:

water pump had crossed my mind but always though the seal went before the bearing...
_________________
1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

RobertN · Joined: 19 Apr 2015 Posts: 142 Location: Lisburn Co Antrim

Guys, think the sqealing pig problem was bad running, as I have adjusted for emissions and got her to 1.2 and she is running smoother and the noise has almost completely gone. Maybe a little rattle from cam cover!

_________________
Robert.
Porsche 924 N/A 1984.
Electrical Engineering Sales to Control panel builders.