Thanks Markus, that explains it.
So it must be one of the two vents on top off the final drive
part of the transaxle.
I guess there are 2 vents on the final drive,
because one of them is for the auto tranny.
From looking in the Bentley,
it must be the vent that is all the way at the top towards the
front of the final drive, where the F.D. is bolted to the
autom. transmission part.
The vent has a little metal cap on it, that can be pried off.
Then one could take a 3/8 id. hose and push it on the
nipple, and blow air or a little tranny fluid through it.
That should clean it out.
Thomas, please let us know if that was it.
Harald
90 westy

Markus wrote:
> My pop's bus appeared to be leaking some oil but we nor my fathers
> mechanic could
> find the source.   When driving, smoke billowed out of the uper rear
> vents...
> Turns out that there is breather valve or something like that on the top
> of the auto tranny.  Apparently as the fluid heats up it also expands
> and air is forced out fo the tranny.  If this is blocked (as appears to
> have been the case on my dad's van) then with no air able to get out,
> fluid travels up the filler tube and pushes past the tranny dipstick
> where the tranny fluid the drops onto the cylinder head and from there
> onto the exhaust header.
>
> THe mechanic cleaned the valve and all appears fine again.
>
>
> Hope this helps someone.
>
> ...Markus