Diesel Engines Adjusting tappet clearances
California Dreamin Probably the single most 'NEGLECTED' part of a diesel engine service (original 1.6D/1.7D & 1.6TD). The Tappet 'check and adjustment' (measuring and replacing shims on top of the cam followers to get the correct valve clearances) was part of every VAG main service for all of their engines using this type of adjustment, however, this involves the use of 'Special Tools' (a follower push down tool and shim removing pliers) Which your 'average' so called specialist VW garage hasn't got so this essential part of the service is often conveniently side stepped ...that obviously doesn't apply to all of course. I would also point out that as this was done annually, the cork gasket and two end rubber seals, were changed at the same time. Unfortunately, now that these aren't changed the CORK gasket goes ROCK HARD and often leads to oil leaks from the cover.
The tappets are adjusted 'HOT' (or at least warm) the clearances are set to: Inlet 0.20mm - 0.30mm & Exhaust 0.40mm - 0.50mm In practice this means: With Inlet valves: the 0.20mm feeler gauge should go in to the gap easily but the 0.30mm should not go in at all.
And the Exhaust: the 0.40mm feeler gauge should go in easily but again, the 0.50mm shouldn't go in also.
In the absence of the correct tools I suppose you could measure the gaps and then remove the camshaft (cam pulley untouched) Once removed you would then need to measure each shim and work out how much smaller/larger that shim needed to be in order to get the correct clearance..all rather long winded compared to using the right tools lol. I used to be able to do this in about 20 minutes (back in the day).
I guess what I'm trying to emphasize is the importance of carrying out this vital maintenance (a least once if you don't know the engines history). Because: At best, incorrect clearances with cause poor running and performance, with increased fuel consumption. At worst, closed up/tight clearances will burn out valves.
I own the tools and a jar of shims but ironically, mines a petrol wasserboxer lol.