RobFrank

I have a 1996 S500 and am troubleshooting a vacuum leak in my pneumatic AC system. The diagrams on ALDATADIY are for a 13 connector bar, but my car has a 7 connector MB#129 800 16 78 that looks like the image below... I cannot find a diagram listing what connections are for what! I am going off the old connections, which had the P - (PSE pump vacuum assist) in connecter 1, ACC Flaps vacuum in #2, vacuum reservoir in #4 and Intake Manifold vacuum in #6. I am suspicious that this might be wrong, since the bottom port is labled "P" and has no valve center, which seems to indicate the "P-" input!

Any help here? I am loosing ACC flap vacuum during accelleration, when engine vac pressure drops and the PSE pump doesn't keep up!

Also, alldata doesn't have instructions on removing the front fender to access the vacuum reservoir! Any tips?

Thanks!

darceyhow

In answer to Valve Block Connections, solved on my 1996 S420 by connecting the Green line to the distribution block to no. 2, and the Pink line to no. 6.
Grey line from engine vacuum is in P and PSE white line is in no. 1.
Air flow all OK now under acceleration!! (Took me a lot of research to come to this logical conclusion - someone had been in the passenger footwell before I purchased the car!)

1999 S500

I had this problem in my '99 as well. The symptoms seem engine related but it ended up being a vacuum leak in the hose connected to the seat lumbar support on the passenger side. We capped off the hose at the PSE Pump and all is well.

Just another example of the "flip the switch to turn on the garbage disposal and the garage door opens" engineering on these cars. It can drive you crazy.