I have owned a 1984 300SD for one month. All the Mercedes I have looked at have vacuum locks. I think this is strange because electric locks have been around since the 50s, I guess. The car has electric windows, so why doesn't have electric locks? Is it because Mercedes doesn't like the click noise that electric locks make? What's your opinion?

By the way, are vacuum locks only found on Mercedes?

Mercedes Man,

This is an interesting question, and there must be a good answer because the practice continued at least into the 90's. The source of vacuum for the locks became an electric vacuum pump on the later cars.

I believe the only reason was that the engineers began to use vacuum to control various functions on the cars, like the automatic transmission, and brakes. Rather than bring another "system" on board, it seems they tried to "simplify" the car by using vacuum for more functions.

I remember when I lived in Germany as a kid the Germans had a saying that, translated to English went like "Why make things simple when it is easy to make them complicated" and it would seem to apply here.

I also think the reason the windows are not vacuum operated is they would use much too much vacuum to operate. In the old days some cars from Detroit used vacuum to run the windshield wipers and they were very erratic, like going up hills the vacuum would die and the wipers would stop or slow to a crawl. The locks use relatively little vacuum to cycle and therefore storing some for that purpose is suddenly practical.

Are the new cars still fitted with vacuum locks? Seems the addition of all the electric gizmos and microchip controlled functions would shift the balance to favor electrical things if they can be made cheaply and light enough. The basic motion of the lock mechanism is linear, which is not the most power dense configuration for an electrically operated device (they like rotary motion as they get good power to weight ratios by spinning very fast). Once you go from rotary to linear motion the greater simplicity of the electrically operated lock concept may get cloudy (you need a gear and rack or something similar).

A good question though. It will be interesting to hear what the group has to say about it. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Another reason is safety. If the car goes in the drink, most electrical sytems will fail, whereas an MB will have vacum to unlock the door while driver/passengers struggle to get out.

I have owned 123 cars for over 20 years and find the vacuum locks to be an advantage.

They have proven very reliable for me. In the few cases where they did give trouble, it was very simple to determine the offending door diaphragm. Once located, these parts are inexpensive and very easy to replace.

Additionally the way they work is so handy. If the drivers door is locked, so is everything else. When you want to unlock something, you unlock the drivers door and everything is unlocked.

My new C Class has programmable electric locks and I don't like them. They are noisy, and when you program them to operate like the 240D(everything locking together), something happens to make them work differently, then you have to figure out how to program them again. Give me the vacuum locks any day.

My $0.02,

FWIW, My mom's 94 VW Jetta has vacuum actuated locks similar to the system in the w126.

__________________
2001 Dodge Ram 2500 Cummins Turbo Diesel - 4x4, auto, 3.54 gears, long bed
-------------------------------------
'92 300D 2.5 Turbodiesel - sold
'83 300D Turbodiesel - 4 speed manual/2.88 diff - sold
'87 300D Turbodiesel - sold
'82 300D Turbodiesel - sold

Here's what Mercedes Benz had to say about that, when the system was implemented in the 600, the "Grand Mercedes."

"The lightest touch is sufficient to close the doors silently. They are hydraulically assisted and close securely. Locking the driver's door automatically locks all doors, the trunk lid and the filler cap."

"Unlike the more widely used electrically operated systems, the hydraulic system has the advantage of greater reliability and safety. In addition, its operation is completely silent. "

I would think that a vacuum solinoid (if that's what it's called) would have a much greater life
expectancy than an electric solinoid.......
William Rogers...

I thought the 600 was fully hydraulic, windows, locks, seats...

John

My 99 ML has electric locks (as opposed to vacuum on my 93 and 95 MBs). I think MB went to electrical when they decided to have the computer manage more "convenience" functions...like locking you out of the vehicle while the engine is running...happened to me twice on the ML until the tech disabled the "anti-carjacking" feature, via a service bulletin...

__________________
2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

I'll say that there two cars I have owned that I could not lock my keys inside. The first one is a 1942 Jeep--it has no doors! The second one is the 1984 300SD. It is impossible for someone to lock their keys inside, thanks to the vacuum locks. Maybe I shouldn't say impossible. Perhaps someone has figured how to lock their keys inside a Mercedes with vacuum locks.

oh it's entirely possible to lock your keys in the car. I havn't done it YET, but i'm sure someone has. all youll have to do is to open the passengers side with the key while the rest of the car is locked, then push the lock button down while closing the door with your keys in the car. Anyone want to be a guini pig?
R

My neighbors have a '91 Audi 100, and it has vacuum locks as well..

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

My 98 E320 has vacuum locks and I prefer them over electric locks. The vacuum locks are quieter and seem more reliable. I also noticed that the front two locks actuate a fraction of a second before the back two locks actuate ( like the rear two locks are delayed).

__________________
Ray
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles

my 82 300D doesn't let me lock any door while it's open.......

__________________
2005 Audi A4 1.8T CVT -Silver/Black "Siegfried"

1982 300D - Silver/Blue "Ralph" -For Sale:
http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/119226-1982-300d-sale.html#post852260

1989 VW Diesel Jetta Blue/Blue "Bodo" RIP

JimSmith: Ever hear of an electrical solonoid? Thats what gets your starter connected to the ring gear. It has a lot more pull than a vacuum cylinder of the same size would have. Remember the maximum pressure on a vacuum cylinder is about 15PSI (atmospheric pressure). P E H