Mercedes Benz W202 C280 Vacuum System Check 

Thank you for posting for this car and staying so dedicated. I am motivated to get mine road worthy again soon thanks to all your videos. Super educational.

Andy, I recently watched your 1995 C280 video for checking the vacuum system. I own a 1995 C280 also and was chasing a vacuum related problem. I have the official MB software that certified mechanics use but it did not provide the detailed information required to troubleshoot the problem. After watching your video that provided the detailed connection description of each port to the vacuum manifold, I was able to gain a full understanding of the problem I was facing. This was the problem and I'm sure it has happened to other owners: the pneumatic system equipment (PSE) pump located behind the passenger side trunk panel was cycling on and off while driving. Also, the pump ran for about 10 seconds after activating the central locking to unlock the doors. The PSE pump has two ports with a yellow vacuum line connected to one and an opaque vacuum line connected to the other. The yellow line feeds all the locking mechanisms and the pump produces vacuum (for locking) and pressure (for unlocking) from the associated port. The opaque line, initially I thought, connected to the rear head rest release mechanism. I bought a new pump because of the faulty pressure sensor in the pump that caused the pump to provide pressure for about 10 seconds after the doors unlocked. That problem was solved, however, the on/off cycling continued while driving. I disconnected the opaque line and the cycling stopped but the rear head rests could not be retracted. The info from your video proved extremely valuable to determine the function of the opaque vacuum line from the PSE pump. The opaque line (you designated it as "white") connects to Port 1 on the vacuum manifold and this port is in parallel with Ports 2 and 3. These two ports provide vacuum to the climate control (Port 2) and A/C vacuum reservoir (Port 3), as indicated in the schematic you provided in the the video. The reason these three ports are in parallel is if the engine vacuum goes below a threshold value, the PSE pump senses the reduced vacuum and activates to boost the vacuum for the climate control systems to operate correctly. Also, the PSE provides vacuum to activate the rear head rest release if the engine is off. Another valuable tip you provided is to inspect the vacuum housing in the area of the pressed ball bearing for cracks. This was exactly the problem I had and why when using a hand vacuum pump no vacuum could be created when connected to the intake manifold vacuum line connected to Port P. So, again, thank you for posting this video. I purchased a new vacuum manifold (all the connecting vacuum lines held vacuum without a hint of leakage) and now the PSE pump is operating correctly. So, if you can provide the source where you obtained the vacuum manifold schematic, that would be greatly appreciated. Thanks again, Andy.

Great to see another video 😃 Hopefully you got it! For the vacuum line removal, I've personally had really good luck with using a 7mm midget wrench 🙂 Just put around the line and leverage it out Where did you get the diagram for the vacuum block? I believe I have the same part in my R129 - but I don't have headrest. Curious what each goes to

Hi Andy. Was wondering if you could help. I found a vacuum port but don’t know where it goes to. Between throttle body and intake manifold on metal casing

Hello Andy. I have 1998 c200 . When i start the engine the boot opens by itself. When i stop anywhere the boot opens again. Can you help me with this issue?

1999 behind that motor is it is a vacuum line you got a

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