Date: Sun, 15 Apr 2007 10:02:14 GMT
From: Paul Halliday <>
Subject: Re: Where does small baby hose from top of Bypass valve go do?? (was: Re: 1995 Saab 900SE Turbo Bypass Valve location??)

in article oi9323pebo7iqfvtol23ikmsjeqi3dr85dnospamcom, Frank Vuotto at wrote on 15/04/2007 05:18: > On 14 Apr 2007 16:15:33 -0700, "robertjm" > <> wrote: > >> OK, so I finally figured out where the bypass valve was. When he said >> it was disconnected he was apparently talking about the small "baby" >> hose that comes out of the top of the valve, not the whole valve >> itself. >> > > That little hose is just a vent to the atmosphere and doesn't go > anywhere. This is not actually right. On a re-circulating valve like you will have on your model, the smaller hose is an integral part of the valve's working. A run of vacuum hose should run from that port up to the intake manifold. Check all the small (4mm) hoses that run off the intake manifold and see if any are not connected. A vac leak will lead to a high idle, poor running and increased fuel consumption, not to mention the car stalling. Some cars can compensate quite well, but best find the errant hose and re-connect it. Contrary to popular belief, the boost pressure is not the main force acting on the valve to "force it open". The vacuum line is the force that actually pulls the bung inside the valve. You can prove this by turning the valve around and putting it on the other way ... It will still work. In fact, on the later 9-3 Viggen model, the valve is actually fitted from the factory "the wrong way round". Take a look at this link: <> Aside from being a good resource for comparing popular market diverter valves, it shows in the table how the valves are best orientated. Notice the standard Bosch valve is best orientated "normally". How to fit in reverse: <> So ... You must have that vacuum line connected for the valve to work. <> >> I looked around the engine compartment and there is a small diameter >> pipe coming out of the right front of the turbo (as you're facing the >> front of the car) which doesn't have a hose connected to it. Is that >> where its supposed to be connected? > > The small hose from the front of the turbo goes to the top (c) input > on the boost control solenoid (apc) > > Here's some pics that will help you out. > > Yup! That's the charge hose ( C ). You can follow the bottom picture to test your solenoid valve, not that we suspect anything wrong with it at the moment. Paul 1989 900 Turbo S

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