Strange knock

[Paul190H]

Evening guys, fitted new plugs, Beru leads, Bosch rotor arm (inc spacer washers) and distributor cap to the S2 tonight. When assembled it started fine but there was a pronounced knocking coming from the distributor. Took it all part, reassembled, still knocking.

Put the old rotor arm on no knocking. Put the new arm on with the old screws and less pronounced but still there.

Any tips, am I not assembling correctly?

Thanks
Paul.

 

[bmnelsc]

IMHO you should carefully compare the old rotor to the new and the old cap to the new. Also look for marks that suggest something is rubbing. From your description, I'd look for rotor mounting screws rubbing on the back plate behind the rotor (you said the knocking is reduced when using the old screws on the new rotor). It may be the mounting tabs on the new rotor are thinner than the old resulting in the screws protruding farther out the back side - you may need shorter screws (or file the old screws down a little being careful to preserve the thread). Or something along these lines. Also you don't say if the rotor (especially) is OPC or comparable Bosch part which may not be EXACTLY the same as the Porsche one.
OR maybe there should be washers between the screw head and the rotor? Just guessing here...

 

[hotblack944]

There are spacers that sit behind the rotor arm on the S2 that you need to transfer over from your old rotor arm to the new. If you've tightened the rotor arm up without them in place, you'll probably find that you've cracked the new rotor arm

Number 25:

 

[Paul190H]

Thanks chaps, both cap and rotor are Bosch. I have also transferred the spacers over. Currently have the old rotor and the new cap and all is quiet.

Will try the new rotor again when I get time and if it continues will send it back for a replacement. Very strange.
Cheers
Paul.

 

[964RS]

https://www.youtube.com/watch?v=sDKO0JEFCzE

 

[bmnelsc]

Thanks for the diagram Jim - the engineering solution is always better than the guess

 

[edh]

I've had rotor arms hitting new caps - you can see the marks on the terminals. (I think tref also had this problem, but was told it was terminal.. (not terminals [] )

 

[tref]

Correct. I changed the engine before I determined it to be a fake Bosch distributor cap. I now refer to it as the world's most expensive distributor cap.

 

[vitesse]

Well at least it wasn't just a full ashtray ,Tref[].The one that fooled me & also John at Unit 11 was the noise the loose steel sleeve that lines the OPRV bore in the engine block,made when the engine warmed up -even that was expensive involving a MK 3 OPRV plus labour plus wasted labour stripping the engine front to check all the pulleys /belts again.[&o]