Chain tensioner noise

Finally, eventually, it all came together. Had a truly nasty chain noise when starting and it would go away when the engine reached idle.
First, took off the chain covers and found the drivers side chain loose on the bottom, tight side, also some scratch marks where it had clearly been scraping the tin. Also ran the engine with the covers off.
For those of you who have always wondered, the drivers side oil drains back down without any excitement. Passengers side needs a bowl but it is a dribble, not a spray.
So,I put in the new tensioners,(87 Carrera), why not do it right?
Note that there was no apparent looseness on either side when starting that is no visible flapping of the chains.
I learned that the internal tensioner spring keeps the chain tight when shut down and starting. The oil pressure adds to the spring force when running and a check valve in the tensioner damps the spring action in the other direction.
So I started it up, quite confidently.

The noise was still there.

During all this of course, had tried every way to zero in on the noise, stethoscope, feeling for it,hammer handles etc and since I had a tensioner failure in my 77, I knew exactly what it sounded like!
So, I next started it with the alternator disconnected and the noise was still there. As a final check, just clutch started it on a hill and as they say in France, Viola. No Noise
Double checked it by feeling up by the starter and sure enough, that was it. Specifically, the pinion was hitting after disengaging. Probably due to worn clutch ball bearings in the starter.
Had it rebuilt and am now living happily ever after.
Ned Monaghan

Jolly good show, Ned!

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'83 SC

ned,nyna11

Good job deciphering how the hydraulic tensioners work! My other full time job, besides a amateur Porsche mechanic, is a timing system engineer, so I know quite a bit about those little buggers. You are correct that the spring inside the tensioner is to keep tension on the chain when there is no oil pressure (startup) which keeps the chain from jumping sprocket teeth and eliminates startup noise (tensioner piston strokes a lot without oil pressure, causing a hammering sound). Once oil reaches the tensioner, the internal spring is just along for the ride as the hydraulic pressure does all the work. The internal pressures are much higher than most would think ... in the 200-800 psi range depending on the tensioner configuration and the internal components, leakage, etc.

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Brian Scotti
'73 S Coupe

[This message has been edited by bscotti (edited 09-07-2000).]