I developed the following digram for the 1975 R107 Mercedes-Benz 450SL so I would have a complete guide should anything go wrong after the car is put back together. This digram does not show the engine vacuum.
LEAK DETECTION:
When diagnosing leaks in the Mercedes vacuum system, a vacuum pump with gauge is mandatory or should you have a smoke machine on hand, that would be the ultimate way to go.
First, start by checking the vacuum tanks for leaks. One is located directly under the front fender on the passenger side above the wheel (LHD). This tank supplies vacuum to the central locking system and cruise control. The other tank is located behind a panel to the left of the emergency brake. This one hold vacuum for the climate control.
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| Unscrew plastic panel and slide away to expose tank. To remove tank and panel, e-brake assembly must be removed. |
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| Passenger side U.S. model |
The vacuum tank for the climate control should not have any issue with deterioration other than the rubber grommet that seals the tank where the vacuum line enters. This part is still available through Mercedes.
The central locking vacuum tank however is susceptible to damage and deterioration as it is open to the elements just above the front wheel. Both the tank and grommet are still available from Mercedes.
A good test to perform to insure proper vacuum is maintained, is to pump up the tank down to 10 mHg. Make certain that your connections are leak free and your gauge is good. The tank should hold vacuum for at least 48 hours without any loss of vacuum. Conduct this test on both tanks. I personally would not recommend using the smoke machine to test the vacuum tanks.
Finding leaks in the system is not complicated, but time consuming. Most often it is the rubber connectors that dry rot and begin to leak. If you have the original system, it is best to test each section of vacuum line by disconnecting, capping and testing one section at a time. The digram will show how the system is divided up throughout the car.
Vacuum leaks are also very prevalent at the diaphragm type locking modules. At 40+ years, the rubber diaphragms are quite crispy and will likely leak. These include the heater tap, fresh air flaps at cowl, passenger side door, fuel flap, and trunk. The passenger side door lock, and trunk lock on earlier 450SL's are no longer available from Mercedes.
Other points of leakage are the driver door lock master vacuum switch and the vacuum switch at the A/C switch. Both switches are identical in function but are designed differently. Both are available from Mercedes.
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| Vacuum for A/C Switch is still available through Mercedes-Benz |
The final potential point of a vacuum leak is the Ford-Philco cruise control unit. The cruise control unit is most likely under the dash behind the glove box on a U.S. car.
It is also wise to change out any check valves. They are located under the hood at the fire wall driver side. Original check valves are black and green while the new ones are blue and black. These are unmetered.
It is also wise to change out any check valves. They are located under the hood at the fire wall driver side. Original check valves are black and green while the new ones are blue and black. These are unmetered.
I've been looking or an easy to read diagram for a while. THX I hope '77 R107 is the same.
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ReplyDeleteGreat insight to vacuum issues. My issue is related to passenger door not locking. So this was very helpful.
ReplyDeleteMan you have really REALLY done a service to a LOT of people who love these cars. I just started my first 380SL and I'm already in love with this car!
ReplyDeleteThanks very much, Jim. They are fantastic cars and, fun to work on and I hope you thoroughly enjoy the process!
DeleteCan't believe I'm only the 4th post.
ReplyDeletePlease feel free to ask questions any time and I will do my very best to guide you in the right direction.
DeleteAlso, anyone ever drop a Turbo kit in one of these cars? (1983 Mercedes 380sl)
DeleteHi Jim, I have twinturbos in my 1975 450SL, and a 5G-tronic gearbox, look on youtube! It works great.//Sten
DeleteJust wanted to say thank you! I found this on google and it has been immensely helpful with my 1976 450sl.All my vacuum lines are screwed up. Excellent work, your diagram saved me hours.
ReplyDeleteDo you know what the part number is for the A/C vacuum switch behind the control panel knob? Photo above with 3 green lines I need a new one
ReplyDeleteThanks for asking.
DeleteDo you have a 450SL? And what year?
I'm sorry I just read your first post. I would call your local MB dealer or Mercedes Classic Center in California 1-866-MB-CLASSIC (1-866-622-5277) and make sure you get the correct part number. If you had a 75 in the same VIN category as mine I would feel pretty confident I could give you a correct part number, but with a different year things could have changed.
DeleteAwesome content. I'm about to go down this rabbit hole on my 1973 450 SL. AC does not work and all I get is hot air even when turned off. Also, the door locks and trunk only lock/unlock with a key. Any idea as to what the part numbers are for the vacuum lines and the connecting plastic things?
ReplyDeleteHello Dave, Thank you very much. Since mentioned the heat issues, I'll address that: It could either be that your vacuum system is kaput and needs a complete restoration or the water tap is kaput. As for the vacuum line it is MB part: 0019973952 White, 0001589835 Purple/Yellow, 0019973952 Clear. To help keep things in some easy order. You will have other colors involved such as red, yellow, green, black. I suggest marking lines that get duplicate colors to keep track of where they go. As for the "connecting plastic things" may I assume you are referring to the black rubber connecting tubes that go from the end of the plastic line to the component? You will also very likely need new check valves at all locations. To get things working you will very likely need to redo your entire vacuum system. If you have further questions I can give you a rundown if you wish to email me at info@camelbackvintage@gmail.com. All the best.
ReplyDeleteMy 1973 seems to differ just a tiny bit...I have two green lines leading back from the firewall where this shows one line leading to controls and another leading to the reservoir in the kick-panel (and no "Y" there either). Does mine not have the climate control reservoir?
ReplyDeleteNote that 1975 (and likely later) has some differences in how the vacuum is routed so there are none of the solenoid's on the firewall that the earlier versions had.
ReplyDeleteI have been desperately seeking AC and Vac diagrams for my 83 380sl R107 and my and 78 450sl R107, if anyone has clear diags of these I'd sire appreciate it! Jim text 218-256-1135.
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ReplyDelete1. Regular Maintenance is key - Be sure to keep up with regular maintenance on your W123. This includes things like oil changes, tune-ups, and tire rotations. Keeping up with regular mercedes service and maintenance will help keep your car running smoothly and prevent major problems down the road.
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