Mercedes W123 Vacuum System - Explained plus Diagnosis

Working on old "tech" can be a daunting experience. In this video i go over the Mercedes W123 vacuum system in particular the central locking system - how it works and how to diagnose a faulty door vacuum element.
The system is brilliant in its simplicity and easy to diagnose if you know where and how to look for faults.

[@guyk2260]

Thank you so much Bruno , saved me a lot of head scratching . You're right it's very logical once you know . 30 minutes with a vacuum pump saw me identify and replace a door switch and central locking back on line again . Much obliged .

[@ifeanyiprosper2775]

You're the best bro

[@arlindocandido5747]

Hello. Where are you located. My father brought a 190d back from Germany in 1993. It is a 1992. It is in very good shape with only 230K but does need some attention and a lving touch to get it tip top. My Dad passed away a few years so I want to keep this car for sentimental reasons. Can you let me know how I can get in touch with you so you can give me a quote on getting this car running in good shape. My name is Arlindo Candido, I live part of the year near Caldas da Rainha, but also in Canada. Thank you

[@heritagesteel1976]

Hi Arlindo, I replied to you via messenger on Facebook

[@jjvanwinckel]

Thank you for this very useful video. I am solving the vacuum problem in my W123 and notice that I have vacuum loss on two doors (rear left and front right). The trunk, fuel filler flap and headlight height adjustment maintain vacuum.
The problem is exactly what you describe: a cracked seal on the top of the actuator.
Can you tell me under what name you found the separate seals on eBay? I may try to repair the existing one first before spending a few hundred euros on new ones.

[@heritagesteel1976]

I haven't bought some in quite some time. I just searched on eBay.de and found nothing, only complete door elements for a 100 EUR a piece...

[@zilizopendwa4644]

Hi, very insightful video, thank you! I have a few questions:
1. I have been losing vacuum in my 230CE central locking system and from my diagnosis I replaced all actuators and all the old tubes. I now believe it's related to the pipe going to the vacuum reservoir at the back. Is there a way of fixing the reservoir vacuum leak without removing the reservoir?
2. What should be the ideal vacuum pressure coming out of the intake manifold into the central locking system?
3. If there's a vacuum leak in the brake booster pipe or intake manifold, will it affect the vacuum required for the automatic transmission?

[@heritagesteel1976]

hello there. Great questions. Start with nr 3. Vacuum affects everything on these cars. Bad brake booster leak, - everything doesn't work properly from the gearbox to the headlight adjustment.
n2: haven't measured the vacuum coming out of the intake manifold. It also varies with engine speed so as long as there's a vacuum you're good to go.
1: use a smoke machine to look for vacuum leaks in the reservoir. Never seen a bad one though. Most of the time it's the t pieces, connecting pipes etc. One possible cause might be also the door actuator on the driver side(forgot to mention that in the video). They fail less often but they do fail as well. With a vacuum gun you should be able to pinpoint correctly to the cause. Often the trunk actuator/gas lid is kaputt:)

[@zilizopendwa4644]

@@heritagesteel1976 Thank you very much for your very useful feedback, I'll do as you've recommended, the smoke machine is a great idea! Much appreciated, looking forward to future videos :)

[@Hope_MO]

Ty keep going 👍💖

[@heritagesteel1976]

I will:)