924Board.org

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

Hey guys, when I Rev the 924 she sounds like a weird "duck quacking" metal grinding sound from within the head. At first I thought it was the metal cam cover was loose or the teeth were touching the cover as I revved her, but it's coming from the head area. When driving the sound is constant at around 1500 revs but goes away as you drive faster through the gears and comes back as you slow down within 2000-1500 revs. Also around 35-40 mph it appears. Sorry it's the only way I can explain the sound without actually posting a video.
Any thoughts or has anyone had this? I could record it, but not sure how to upload a video to the forum.

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

Ozzie · Posted: Sun Jun 28, 2015 6:14 pm Post subject:

cam belt tensioner?
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

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

Hey Ozzie, had cam cover partly removed to check, I can turn the tensioner quite easily, maybe I need to check the tension measurement? The sound isn't like a loose alt belt squeal but more of a "grunt" like metal vibrating sound. To get at it properly it looks like I need to remove the alt belt, or is there another way??
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Robert.
Porsche 924 N/A 1984.
Electrical Engineering Sales to Control panel builders.

morghen · Joined: 21 Jan 2005 Posts: 9095 Location: Romania

Check if the bearing caps nuts and bolts of the cam train are nice and tight. They dont need to be too tight so dont over torque them(look up the correct torque)
Also check the valve cleareances.
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Supercharger and EFI kits
https://www.the924.com

Fasteddie313 · Joined: 29 Sep 2013 Posts: 2595 Location: MI

Good call, I should also get in there and re torque my cam caps and head studs just to be sure, recheck lash, also install my cam cover gasket set thats been sitting for a year but straight black permatex has proven to seal very well as is in lieu of gaskets when I didn't have any..

I also deal with low rpm specific rattles, steering column still needs a clamp bolt, still something small in the exhaust at about 1200, rattles/vibes are greatly reduced if mine is kept over 800 rpm or so, too low idle = lots of vibration in my case so I keep it just under 1k by the tach..
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80 Turbo - Slightly Modified

Ozzie · Posted: Mon Jun 29, 2015 1:45 pm Post subject:

The tensioner has a single bearing in it and can run dry and make strange noises. Over tightened they really groan.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

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

thanks Ozzie. Will check everything out later. I have just one question, if I decide to replace my cam belt as a matter of service whilst I have the cover off do I need to reset the timing?? or can I just put a new belt in??
Thanks.

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

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

Found it! After poking around the exhaust manifold heat shield I noticed it was cracked and the right hand end nut was loose. So I removed the broken piece and started her, revved and went for a spin, hey presto all gone!! How much of a nuisance that was, but just goes to show, such a little thing can make you think all sorts of engine problems!!
Just need a new heat shield, breakers yard for me!!
Thanks for all your posts! Still gonna renew the cam belt as I don't know when it was done.
_________________
Robert.
Porsche 924 N/A 1984.
Electrical Engineering Sales to Control panel builders.

Ozzie · Posted: Tue Jun 30, 2015 8:10 am Post subject:

When you fit the cam belt you only need to align cam and crank when fitting. (both have to be on the alignment mark)
Timing should not need adjustment.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

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

Cheers Ozzie.

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