Z1OwnersClub GB

Hi Guys,
76 A4, I've got what sounds like a top end rattle. Cam cover off and jockey wheel seems to be fine. Checked the shim gaps and no 3 cylinder seems to be way out. The gaps should be between 2 and 4 thou, right?
Inlet cam, 1 = 2.5, 2 = 2.5, 3 = 5.5 and 4 = 2.
Outlet cam, 1 = 3.5, 2 = 4, 3 = 5.5 and 4 = 4.5.
The noise definitely seems to be coming from cylinder/s 3 and/or 4.
Before I get to concerned, and while I'm waiting for shims and tool to arrive, just wondering how noticeable/audible that excessive amount of gap would be?

Thanks, Warren

Yes, some are a bit on the wide side but probably not enough to rattle too much, that is more likely to be caused by a loose cam chain. Is it a tic tic or a rattling noise? Have you checked the adjustment, have you got an auto tensioner or manual? Adjust according to the manual.

If you are a member of the OC, Jerry can supply exchange shims. Don't forget to keep a chart of your gaps and shims so you know where you are.

HTH

Thanks for the reply, mines got a manual tensioner, already checked and adjusted. Its not a ticking noise and not a knocking noise, somewhere in between. Compression is fine on all cylinders. Does the rev counter drive ever fail and become noisy? The rev counter still works.

A little more info on this as I listened to it at the weekend, it all sounds very quiet on idle but as soon as you rev it, it starts to knock cams appear to be nice and snug, even hot the valve gaps were over what they should be cold.

Hi Kev,
Thanks again for your time over the weekend. I'll re shim it and see what it sounds like then.

https://www.hightail.com/download/UlRUR ... OFJYd3NUQw
30 second video download of engine noise.
I've done the shims and as you can hear the noise is still there. It does sound a lot worse on the video than it does in real life.
The up side is throttle response is better with the correct gaps!

do the cam buckets turn freely in the head? could be a broken inner valve spring

Yes, they do seem to. Apart from pulling it apart, any other things worth checking first?

are the camshaft caps tight = no striped threads? what are the cam bearings like? have you checked the chain tension with the cam cover removed & turned the engine fully 360% could also be valve guides

Cam caps tight, no striped threads. Cam bearings appear to be good and the chain tension is also good. New valves and guides and seats re-faced.

That's not great, unfortunately its a possible top end strip by the sound of things.

Have you isolated which valve / area (screwdriver to ear method works well) is causing the issue?

Take the cam cover off then take the cam out then pull the bucket out to make sure is not sticking / broken / doggy shim / missing valve collet and try an see if there is a broken valve spring before stripping.

It may be that a valve guide has cracked / failed.

If you can not isolate it then stripping may still be a stab in the dark but it sounds like you will have no other option.

zpower wrote:Have you isolated which valve / area (screwdriver to ear method works well) is causing the issue?

Take the cam cover off then take the cam out then pull the bucket out to make sure is not sticking / broken / doggy shim / missing valve collet and try an see if there is a broken valve spring before stripping.

It may be that a valve guide has cracked / failed.

If you can not isolate it then stripping may still be a stab in the dark but it sounds like you will have no other option.

If a bucket was sticking it would misfire on that particular cylinder wouldn't it, which it is not doing.

Took the cam cover off again today. Checked the torque on every nut and bolt I could find. Couldn't find any play in any cams / carriers. All the buckets moved nice and freely. Gaps are now correct. Put it all back together, took out the tacho drive, started it up and depressingly the noise is still there. Risked letting it run for several minutes whilst having a good listen and search around. It's definitely coming from the front right side but I couldn't pin point it with the ear to a screw driver method despite putting it to every surface that has something moving beneath it. I'm not convinced its valves or guides after listening to them. It isn't chain related. It isn't bore related. Its not a rumble and I couldn't find any play so I doubt its cam bearings but as they are cheap I guess it wouldn't hurt.
It is certainly more evident on over run.

Probably a bit of "end float"