I recently swapped an engine (with the turbo) and without the intake manifold from a 1985 740 turbo into a 1988 760 turbo. I kept the original intake manifold in the 1988 760 but I disconnected more hoses than I needed to in order to easily move the manifold out of the way. I now wish I had documented things a little better.

I have one left over vacuum hose. There are 3 vacuum hoses attached to fittings at the center of the intake manifold located one on top of the other. These fittings point towards the engine. The hose on the top fitting was never disconnected and leads to a T and then through a couple of check valves to some plastic hoses. The hose on the middle fitting goes to a red and gray check valve and then on to a diaphragm bolted to the head that appears to operate a valve between the turbo intake and outlet.

I have no idea what the bottom hose attaches to. On the 1985 740 it went to the firewall on the drivers side However on the 1988 760 there is nothing there for it to connect to there. There is an available fitting on a device bolted to the left inner fender with some electrical connections and a vacuum line leading to a T. One hose goes from that T to a vacuum motor that is attached to the throttle and the other disappears down by the firewall on the drivers side.

Where does the mystery hose go?

 

Well the ones connected go to the climate control vac and to the CBV (compressor bypass valve) it sounds like. Is there any way you can post a picture or two?

 

I finally got it started and the manifold pressure (boost) gauge does not work. Is the gauge mechanical or does it get an electrical signal from a transducer? I assume this hose goes to the firewall somewhere, but I can not see where. I am reluctant to drive the car because I am not sure if the ignition computer is getting a manifold pressure signal. When I have more time I will post a picture.

Does anyone have a diagram of the vacuum hoses for this car?