BC

Anyone have any ideas?

IcemanG17

does it change with RPM? If it does...its bad news....since it sounds like rod knock to me....... When the 1st engine in the 928 Estate died...it sounded alot like that

Hilton

Is there a belt on the airpump? (likely on a mechanical fan clutch car like this).

Remove it for a quick test. Switch to shorter belt that avoids air pump if it is the problem.

blown 87

Rod knock, fan hitting the shrowd, broken flex plate, lots of things can cause a sound like that, but it sounds expensive and a lot like a rod from here.

BC

That was my first thought. BUT... the reason I do not believe that it is rodknock is because it is at a faster rate than the rodknock I have heard before, and its clearly coming from the top of the engine. But of course I could be wrong. Infact many times I am. But I get some right.

Rod knock would be at the same speed as piston slap, which sounds like this:

BC

Okay. The noise is not the fan. Its a 5spd, so it doesn't have a flex plate.

It may be, and if it is, I'm in trouble. But the speed doesn't seem like it. Its almost like a loud injector, but its not that I guess. What about a timing chain problem?

neilh

Timing chain broken link flailing around and hitting the underside of the cam cover?

blown 87

What is the history of the car?
Any metal flake in the oil?
The problems when trying to figure out a issue like this is the fact you need to run it to track the noise down, and you do not know how far away from a total failure you are.

I would heed the advice from Mr Merlin and check the cam gears and hubs before running it again.
But I have heard 928 engines with broken hubs that only missed, and did not make any noise.

BC

I think it sat for more than 3 years. There was supposedly some top end work done at some point. Oil is clean from what I can tell.

WallyP

While it is unlikely, given that you said that the noise sounded as if it was coming from the top of the engine, I had one that sounded like that due to a broken strap on the pressure plate. The strap pivoted out and hit the ribs inside the bellhousing. A quick look inside the clutch housing will take care of that possibility...

SteveG

Stethoscope or hose used as same might locate the spot.

SQLGuy

If it sat for three years, maybe it's just multiple collapsed cam followers?

BC

I was thinking of the stethoscope idea. Where would I get one of those?

BC

Can you conceivably run the car at idle with the cam covers off?

neilh

http://www.harborfreight.com/catalog...&q=stethoscope