[Vwdiesel] Head/Engine rebuild lots of questions

[LBaird119 at aol.com]

In a message dated 5/25/2002 8:08:32 PM Pacific Daylight Time,
vanagon at columbus.rr.com writes:

>     Here's where the questions begin:  The heads are cracked between the
>  valves in each combustion chamber, not huge cracks, but maybe .5mm wide
from
>  valve seat to valve seat.  Would this alone cause compression problems and
>  loss of power?

  This is fairly common/normal.  IF one of these cracks was deep enough to
actually be a problem, it would leak water more than it would leak
compression.
>
>  The valve seats seem okay and the stems aren't too carboned up.  One intake
>  valve stem is a bit oily though.  Oddly, the #3 compression chamber didn't
>  have much carbon at all coating it.  #1 and #4 looked fine, nice coating of
>  carbon, #2 and #3 show a bit of aluminum corrosion.

  Kind of sounds like a blown head gasket on #2 and #3.  Water getting into
the chamber.  It would have had highly pressurized coolant.
>
>      While I had the head off, I figured that I'd try to measure the piston
>  crowning for the next head gasket.  I think that the dealer put the wrong
>  gasket on, as theirs had holes instead of notches.  Not having the proper
>  dial gauge, I tried using a straight edge and feeler gauges.  I'm pretty
>  sure that I didn't get accurate results as I measured all four pistons as
>  crowning at around .030", well below the threshold for the one notch
gasket.
>  Is this a bad assumption? I'll probably get the dial gauge to time the pump
>  anyway.

  I just looked and I think you have up to .050" for one notch.  I usually
use
a dial caliper.  Not as precise as a depth gauge either but it works.  :)
  Holes vs. notches is a manufacturer thing.  Correct number is all that
matters.
>
>      I'm guessing that I'll have to start with a rebuilt head, and the
>  rebuilt injectors I just bought, assemble the engine and see what happens.
>  During one of the discussions of the condition of the engine with the
>  service manager at the dealership, I seem to remember being told that the
>  compression problem may have been a bottom-end thing.  What are the chances
>  of this?  The van has ~114k on the odometer.
>
  Worn rings will indeed cause a compression problem.  Your head should
be rebuildable.  You'll need new guides most likely.  Check wobble with
the valves most of the way in.  Exhaust valves usually need replaced due
to stem wear.  The seats and intakes can be ground.  Then you need to
grind the stem length to get you to the proper cold setting on the assembled
head, with either baseline 3.70mm/3.75mm shims or using what you have.
I'd sure be inclined to use new rings.  I'll plug Total Seal rings again her
or at least sending them your second rings for their modification.  Much
less blowby and with the load a Vanagon gets...  Of course you'll be into
the rod bearings so they should be replaced if needed.  If they need it then
the mains will need checked too.  Intermediate bearings should be done
if the others need it but that requires pulling the engine.  ;P
  If the head's not disassembled then you can check valve clearances and
rotate the cam to check the condition of the seats and valve faces.  If the
valves aren't too tight and the seats and faces don't looked cooked then
it's not likely leaking valves.  :)
     Loren