[Vwdiesel] Head Removal Surprise

[Michael Alexander]

The engine was bought from the local VW dealer as a factory rebuild about 8
years ago. It sat around for a couple of years before being put into an 82
rabbit. The timing belt was changed once by me about 2 years ago. The engine
runs strongly but developed a coolant leak into one of the cylinders.

The plan was to change the head gasket. The muffler clamp on the exhaust C
clips worked well. Finding the spline wrench for the head bolts was a small
adventure. To my surprise, the pistons all had an imprint of the exhaust valve
on the top surface. The valve surfaces seemed normal. I hauled the head into
the local VW mechanic and he recommended replacing all of the exhaust valves.
His reasoning was that the valves could have been stressed by the contact and
could break later on down the line. I do not have a problem with this. 

My question is how the contact could have happened. The engine has never been
over-revved. I used the pin, plate and timing mark to keep the cam, pump and
crank in the proper relationship when I changed the timing belt. I rotated the
engine by hand for a few revs with no contact after the timing belt change.

Any thoughts?

m alexander