D.J. noisy valve train

[busboy1303]

Hi there! Been lurking here for a while and been mightily impressed by the amount of knowledge that you guys have. Thought it was about time I joined up and shared my problems with you (the VW related problems anyhow).
So here's the thing; I rebuilt the 2.1 DJ in my van a couple of years ago. It runs absolutely perfect with no problems what so ever. The only thing is, the valve train is noisy when it gets warm. Start it up from cold and it's dead quiet. As soon as it gets a bit of warmth into it, it starts to get noisy. Before I touched the engine it used to run really quiet all the time. It's not a completely unpleasant noise like a lifter that's drained off, but just a kind of clatter from the valves. It's starting to bug me now.
It's got loads of oil pressure
I've tried it with 15w/40 and 20w/50 oil, no difference
It's got new hydraulic lifters, although I've recently tried it with the old ones back in it and it's exactly the same
I've done the tappet set up according to the manual of no valve clearance and then screw in 2 turns
It's got a new cam
The heads were fully rebuilt with new guides etc
Any ideas?

[tencentlife]

Cam endplay.
Gear lash.
Piston slap.

[busboy1303]

Hi, thanks for the reply. It's definitely more top end around the cylinder heads.
Now I know it could be literally anything. I've built a few engines in my time, admittedly mostly more modern stuff, and I was pretty confident I'd screwed it all back together correctly. It had all new bearings, and gears, oil pump etc and I measured all the clearances. With it getting noisy when warm I assumed it was some kind of oil pressure problem, but I've checked it and it's ok. I pretty much went over the whole thing. Had the rods re conditioned, replaced the rocker studs because they were mushroomed. There's obviously something I've overlooked somehow.

[syncrogreg]

Stock dished cam?
If not, which cam?
Which gear?

[busboy1303]

I don't know the specifics of the cam I used. I bought it directly from a major well known VW engine re- conditioning company here in the UK. They apparently use it in their engines, it's supposedly a new direct copy of the original. The gear came with it. I checked the actual timing of the cam with a gauge and it was spot on.

[buildabiggerboxer]

o.k, now you need to pin the noise down exactly, you will have to idle the engine and apply pressure to each rocker in turn and listen for a change in the noise, it will help to drop the idle speed right down for the test, wear a heavy glove and push on the rockers with some rag until its isolated the noise, messy but needs must, it wont be piston slap because that lessens with engine warm up.

[busboy1303]

Ok so I've checked everything. I've pressed on all the rockers in turn and it made no difference. The noise does sound like it's coming from the heads though. Not one isolated valve, but maybe all of them. I've had the rockers off it again and checked them. Checked the rush rods are located correctly. Set the rocker basic settings again, checked for excessive play in the valve guides. Everything appears to be ok. Something is telling me it's the cam. Like maybe it's a poor profile on the ramps causing the valves to close too quickly.

[busboy1303]

Doesn't explain why it only does it when it's warm though.

[Dougs Auto]

worn out wrist pin to pistons will cause a knock when warm. piston slap goes away when the engine warms up. the piston expands and the pins get looser makes more noise

Doug

Just my uneducated opinion

[buildabiggerboxer]

How odd this one is, now try dropping the HT leads and listen for any change in the noise, carefull, they doen't half pack a punch, pre loosten them at the cap to save fiddling is safest. oil supply to the heads look o.k?

[busboy1303]

Thanks but already tried that. No difference. Managed it without getting a shock too. Plenty of oil to the heads. Got it sprayed all over my face whilst testing the above.

[AMBROSIA]

What about a weak valve spring?
Had this on an aircooled engine recently that got noisy when warm.

The springs where fine for the rebuild but got noisy after running it in.

[busboy1303]

Hmm interesting!
Thanks Ambrosia. How did you find that out? You just had one weak valve spring, and replacing it/all of them fixed it? If so I'm thinking a lack of control of the valve is causing the valve to jump over the top of the cam lobe and snap shut, hence the noise. Sound possible anybody?
Mine are still the original springs. Double don't forget. I think they'd all have to have weakened because the noise seems equal from both heads.
I'm definitely liking the theory, and even if it's not the springs, it kind of supports my other theory about a poor cam profile.
Thanks. More to think about.

[AMBROSIA]

I had the same head scratching as I could hear louder tapping once the engine was warmed up.
Having checked the usually things it was a case of removing the head for further investigation.
If you are getting noise from both sides then it's unlikely to be this though
Mine was clearly on one side and replacing this weak spring did stop all the noise.

I spoke to Marco Mansi a few years back when I took my wbx bug to the volksworld show and he said that almost all these engines have a distinctive knocking noise coming from the case that he has never really got to the bottom of.
Even engines that have had a full rebuild suffer from it to some degree.

I'd be tempted to pull the lifters and check for any early signs of face wear if this camshaft is questionable.
One other thing that has been discussed on this forum is the problem associated with poorly ground cams and the effect on hydro lifter operation.

Where did you source this cam from?

[busboy1303]

Thanks Ambrosia. Strange how the noise only happens when it gets warm. I was going to try and change the springs without removing the heads but I've dropped the whole thing out for a full strip down next week. It would have been interesting to see if it had cured it.
I've read a lot of posts regarding poor cam machining and how you need to check them before installing. I checked the basic timing of mine but that's it. Makes me sound like an idiot. In my defence though, I work at a main dealership. If I change a cam at work, I order direct from the manufacturer and it comes perfect every time. I guess things are a little different when you're buying aftermarket parts when the original ones are no longer available. Also I guess it's asking a bit much to expect a set of 100K miles valve springs to work in harmony with a nice fresh cam profile. You live and learn