The locknut is indeed on the injector side of the rocker and its function is to lock the ball pin which is threaded into the end of the rocker and which presses on the plunger of the unit injector - inside the big spring. The ball pin is ball-ended at the injector end because the rocker pivots and the injector plunger slides.

Think Morris minor tappets, the arrangement is precisely the same.

After 100k odd miles inside a diesel engine there's always the possibilty that the locknut has loosened and the pin has unscrewed a little - giving the grandmother of all wide tappets. If the pin unscrewed completely, there would be no fuel from that injector.

If the clearance is only a little wide, VAGCOM won't necessarily reveal this as there is a generous allowance on this engine to enable it to be fully supplied with fuel over a wide timing variaton + the "KW" error associated with the cambelt installation.

659.

The PD engine cuts the fuel on the overrun. The injector solenoids are not energised and the fuel is discharged at relatively low pressure to spill.

Mechanically unloaded pump plungers will not make anything like the noise of a pressurised plunger when struck by the ball pin. Worth a look.

659.

Sussed it. Feel like a bit of a pleb for not noticing it the first time i had the rocker cover off, but its a proper 'jeeezus' moment. I decided to check all the torques on the bolts to ensure nothing had come loose. That was when i noticed that one of the four bolts holding one of the injector rocker rails on wasnt there!

Then panic set in - if it wasnt there.. where the feck was it. Out of sheer and blinding luck, i felt right down into all the oil ways and nooks in the head and found it, and managed to get it out with a circular magnet attached to some strimmer wire (didnt want more metal flying about in the engine).

One lucky escape.

Thing is, looking under the head of the bolt i found its flush. The bolt left in the engine is sat about 2mm into the hole where it sits. So i started fishing again and found nothing more after an hour. So i took the oil filter off, and again came up with nothing. I intend to get the other three bolts off and see if the head of the bolt matches up to the rest of it. If not, ive got about 2mm of metal kicking about in the engine somewhere and its sump off time soon as it stops raining.

Im aware these are stretch bolts and have to be replaced each time, so im *hoping* that it does match up once i get to it. Four new bolts on order from VW cost £5.03 each +VAT. Heres some horrible pictures:

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Edited by foshizzle on 16/08/2011 at 18:08

Thanks for the reply, ive ordered the full four as im going to have to take the rocker arm off in order to remove the snapped stud.

Ive also heard that people have stripped the threads off the head torquing these down.. have you ever encountered this?

thanks pal, im just waiting for VW to come up with the goods and then ill report back if it all goes to plan.

Time I think to make a very careful check.

I can tell you from experience that VAG documentation is not free of errors - some serious.

20 Nm + 270 deg sounds very unlikely for such a short M8 bolt. I think that tightening to this figure would be a very risky strategy - the thread depth in the aluminium head is not great. If you have heard of thread damage occuring at this point, it could well be the result of a VAG documentation error somewhere that has caught others.

Go carefully indeed - I'd stop at 90 deg first. If you get an authoratative value perhaps you could post it here - I've assembled these to 20 Nm + 90 deg without problems.

659.

Nm = Newton meter
nm = nano meter

It's interesting to see that there have been revisions in this area.

I think if I were in your position I would talk to a knowledgeable and interested Independent who has seen a fair few of these engines and who is aware of the updates. The problem with the dealers is that they are programmed by VAG to operate like zombies and any errors just get repeated, let alone reported back. The interest factor is generally not there either, so jobs are seldom optimally done.

Use EKTA to make sure you have the latest revision of the bolts - EKTA seems to be one error-free area of VAG's system. Note the part number and then do your research to get the tightening procedure.

The loadings in this area are very substantial - injection pressures on a PD can approach 2000 bar (hence the efficiency) and there is almost no margin for errors. You may now consider replacing all of the rocker shaft bolts.

659.