Date:         Fri, 28 Sep 2007 11:15:49 -0400
Reply-To:     Jake Beaulieu <jbeaulie@ND.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Jake Beaulieu <jbeaulie@ND.EDU>
Subject:      Re: Plugging leaks in intake manifold

>> On my 1.9L, there is a strong suggestion that I have a leak in the
>> intake manifold. This based on pinching the auxiliary air regulator hose
>> when the engine is cold and not having the engine slow, as Bentley's
>> says it should.

Mike,

I believe a good test of the air intake system is to measure the manifold
vacuum you are generating.  I combed the archives on this topic a while
back it seems that anything over 18 in Hg is pretty good.  Below 15 or so
and you should really go searching for a vacuum leak.  However, low
manifold vacuum can also result from air bound or poorly adjusted
lifters.  This topic is covered in Boston Bobs article on hydraulic
lifters that can be found on his website.

Have you checked the bolts that secure the intake manifold to the head?
Thse suckers do come loose sometimes and can cause a vacuum leak.  There
are also posts in the archives where folks have used rubber stoppers and
compressed air to find vacuum leaks.  The basic idea is that you plug up
various openings with rubber stoppers, spary all potential leaks with
soapy water, then pressureize the system.  If you are leaking you will see
bubbles forming.  Of course, you can always start spraying stuff with carb
cleaner and listen for a change in the rpm's indicating that the fluid got
sucked into the intake system through a leak.

I think you approach of completely refabbing the air plenum is a good
one.  I have a new gasket that goes between the throttle body and air
plenum that I have been meaning to swap in.

good luck,
jake 82 AC Westy