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isuras2 · Joined: 17 Jun 2005 Posts: 458 Location: Phoenix, AZ

With the engine running, it sounds like knocking coming from under the valve cover. The tapets/valves are adjusted to within spec. Could the knocking sound be and exhaust leak between the manifold and head?
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Rob
'80 931 (sold)
'80 924 NA (sold)
Former Omaha Crew

Smoothie · Posted: Fri Mar 16, 2007 3:07 am Post subject:

Could be that.
Arcing spark can be suprisingly loud and sound like a knock or loud valve tap, so check for that too.
Do you notice it just at idle with your face in the engine compartment? -Or can it be heard also while driving? How does the sound change under accelleration/load.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

isuras2 · Joined: 17 Jun 2005 Posts: 458 Location: Phoenix, AZ

I would doubt it is arcing spark as I have not been shocked yet and the wires are about 1 year old (NGK wires). I believe it changes with RPM, but I haven't really been able to listen too much to it while driving because the exhaust out back is loud so other sounds aren't as noticeable.
_________________
Rob
'80 931 (sold)
'80 924 NA (sold)
Former Omaha Crew

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Well, since you already have a loud exhaust, just get a loud stereo and the noise will be gone!

In seriousness, though, my car makes a bit of valve racket too. . .probably sounds like imminent destruction if you have never owned a solid lifter car before.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Smoothie · Posted: Fri Mar 16, 2007 5:19 am Post subject:

Good point, it might just be normal.
If you could hear it from the drivers' seat and it got much louder under load, then I'd've said bad connecting rod bearing. -And knock under load, but not at idle can be too-low octane fuel, too-advanced timing, and/or carbon build-up on the pistons-valves-head.
-But loud valve train noise (clicking/ticking) with the hood up and your ears right there is pretty much normal with the 924NA and 931.

Ouch. This was my 5000th post. I should get a hobby, eh?
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Benino · Posted: Fri Mar 16, 2007 5:49 am Post subject:

yup. My 924 made that noise even with a freshly rebuilt engine, valves adjusted, and new gaskets and seals everywhere.

the loud stereo solution "fixes" lots of problems.

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1980 Porsche 924 N/A USA
1980 Porsche 924 turbo USA
1987 Porsche 944S USA

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

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

this might sound a bit crazy but check your alternator...start the car with the alternator / water pump belt off....listen if it still knocks. i tought my engine was shot...because the knock was near the tappets....but it turned out to be the alternator.
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Supercharger and EFI kits
https://www.the924.com

Smoothie · Posted: Sat Mar 17, 2007 2:42 am Post subject:

Good point again.

A bad water pump will sometimes knock too.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

isuras2 · Joined: 17 Jun 2005 Posts: 458 Location: Phoenix, AZ

I will have to try that next time I start it up. I wonder if getting a loud stereo along with the loud exhaust will help get rid of the rad. fan whine.

_________________
Rob
'80 931 (sold)
'80 924 NA (sold)
Former Omaha Crew