update on my 91 200tqw boost issues

Dan Simoes dans at audifans.com
Fri May 24 11:07:48 EDT 2002

OK,  a couple of things to report in the exorcism of my 91 200tqw.

- To build a pressure cap (to check for air leaks) you can indeed use a
3" Qwik-Cap, found in the plumbing aisle of Home Depot, and add an air
valve to the cap (found in the tool corral).  I also used a 1/2" washer
inside the cap and since I couldn't find a nut of the right size, I used
a F-F coupler to tighten the valve in place.
Loosen the clamp enough so you can get the intake hose inside the cap,
as snugly and as far in as it will go, then tighten the clamp.  I also
used the air hose to provide extra support bracing the cap in place.

- My pressure check found (surprisingly, at least to me) no leaks, other
than the oil cap gasket and the dipstick, which I had removed and sealed
with duct tape.  I ran around 10psi (or 1 bar as indicated on the dash,
with the key on but engine off).

OK, no leaks.  What else could it be?  I had the intake hose off
already, so I removed the airbox cover.  Air filter is dirty and from
1997 (!) but it wasn't that bad, really.

I decided to check the bypass valve.  I could not get the little crimp
clamp off in place (especially since I had recently retightened it when
replacing that vacuum line) so I removed the valve completely, pried the
clamp and hose off, and took it inside to test it.

I blocked both openings of the valve using my hand and the bench, and
applied vacuum with a Mityvac.  The gauge would go up to 5 and quickly
fall back down, and the plunger inside barely moved.

Conclusion - as per SJM's site, sounds like I need a bypass valve.
I'm going to try to source one today.

I found this page:

and reviewed SJM's site.
Sounds like I can get a stock replacement at the dealer (034 145 710A =
bosch 0280142108) or the upgraded stock valve (034 145 710N = bosch
0280142110, possibly equal to bosch 0280142114).

Anyone have any more accurate info or suggestions on what valve to get?

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