Date:         Wed, 30 Nov 94 9:09:44 PST
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         macklow@sybase.com (Jim Macklow)
Subject:      Re: blow-by to the limit ... what limits?

> 
> Hello vanagonites and Rick,
> Has anyone here actually gone ahead and ignored the wicked blow-by and
> kept adding oil to their diesels?  What is the eventual outcome of
> blow-by?  At what point will the vanagon engine absolutely have to be 
> rebuilt?  You might wonder why I'd ask such questions.  Well I would
> almost swear that my blow-by pressure actually turns my oil filler cap.
> Almost, but then again I could always make the same mistake not once, but
> twice...

Well, this is experience from a Diesel Rabbit I used to own...  Excessive 
blowby combined with crappy heads (leaky valves/valve guides) forces a lot
of oil into the cylinders.  Past a certain load/rpm point, there is enough
oil being forced into the cylinder to continue the combustion process, even
if the diesel fuel delivery is reduced or shut off (via ignition switch).  This
is called run-on.  It feels like a nitro burst, and as you look in your rear-view
mirror, you see large clouds of smoke billowing.

Running the car in this state is bad because you're burning up all your oil at
a very rapid pace, and you no longer are rpm-limited to 4800 (5200?) rpm, either
of which will cause engine failure in a short (seconds?) time.

My rabbit had this problem.  It was solved (reduced?) not by an expensive valve or
ring job, but by buying a kit from the dealer, which runs a hose with three ends
(it's a tee), connecting the crankcase (where the vacuum pump is connected) to the
valve cover, and the third end attaches to the air intake manifold.

This little gem cured the run-on problems I had.  However, it meant that I had to
buy air filters twice as often as oil changes, since the air filter would get oil-
soaked in no time.  I ended up buying the gasoline Rabbit air filters, since I was
replacing them so frequently, and they're half the price.

-Jim