Leaky intake manifold?

[crowinghen]

Here's what we have found today in our search for the source of intermittent loss of power/hesitation and surging of our 84 van

1- think we Hear a whoosh near intake manifold
2- we spray brake cleaner on the underside of manifold- big white plumes of exhaust come out the tailpipe
3- no change in rpm's at all when doing this

does this sound like a leak in the intake manifold?
also hubby blocked the air cleaner intake-- no change in van running-- shouldn't it stumble from loss of air?

thanks!
susie
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1984 Westfalia a work in progress " Butters"

[reluctantartist]

Have you replaced all of the vacuum lines? Also the throttle body seal could be bad. It sounds like you definitely have a major vacuum leak which will cause drivability problems.
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1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them.

[crowinghen]

[Wildthings]

Did you replace the four manifold boots? They slowly get stiff with time and don't seal well against the plenum and runners. They also can become porous. They are only a couple of bucks each. If the boots are good you might check for cracks in the bottom of the plenum and make sure the seal for the throttle body is good.