[Vwdiesel] Decoking pistons [ photos]

[mark shepherd]

Hmm no titles are descriptive.

I'll rearrange them in the future.The photos show state of pistons when I
took the head off .
The exhaust valve marks that have been from them tapping the pistons for
over two years, and some 25000 miles! There are some views of the stuck
rings, and one of the sets of rings placed in a cylinder to see the huge
gaps. I have changed the 2 hole to a 1.5 5 notch to try and gain a few thou.

http://img809.imageshack.us/f/imgp9942.jpg/

Truely impressed by the ability of this engine to run with 200, 270 160 and
200 psi on a compression test.
As the bores looked good when I skimmed the head a few years ago; I never
removed the pistons to check, but some months later, I managed to rig up a
compression tester that gave about 280  to 300 psi  for the cylinders. At
the time I assumed the low values were down to errors in my modified
injector adaptor, because the engine ran so well, and gave reasonable mpg of
43 to 48. Hard starts only appeared back in July, but mileage never
diminished.
Engine now been running for about 300 miles and first fillup gave me 51mpg
for mixed trips, at least half of them a mile or so only.
Hopefully it willl get better, but if this is the worst, then that's a 20%
improvement

Mark



>
> Greetings,
> Hopefully someone will be up on the other side of the world.
>
> Just taken my pistons out for a rering, I was having a 'little difficulty 
> starting. Fuel economy averaging about 45 to 48 UK mpg. 3 pistons have 
> single stuck rings,top or middle some of the gaps could be as big as 
> 1/16th- 1/8th of an inch!!
> Bores good, and hastings rings fit to middle of VAG gap spec.  Pistons are 
> great and so are all bearings. It loks like my nocking for the last 20 to 
> 30 ooo miles was exhaust valve clash. I always set belt accurately, but I 
> overskimmed the head, and so this mayexplain that.
>
> However my question is this.
> Should I remove the thin layer of carbon deposit between top ring and 
> piston face?
>
> Regards
> Mark
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