After the car is parked for an hour or two, none of the other locks open. (only driver's door.) I'm thinking that the rubber diaphragms in one (or more) of the doors has corroded, can anyone help me with this? I doubt it's the main vacuum pump, because the engine doesn't hesitate to shut off. Thanks for any help.

I have not dug into the vacuum lock system yet, but I know it is only a matter of time before age of my car catches up with this system. You obviously have a small leak. The diaphragms would be suspect as well as the lines. Get a schematic and one of those hand operated vacuum pumps with a gage and start locating the source of your problem. If you plan on keeping the car a while, it might be worth it to overhaul the whole system, such as replace all diaphragms, hoses etc.

Have fun!

Speedy,

Is your 300 turbo a W123 or W124 model? Considering your name it has to be (at least) a W124...

There is a difference between the W123 and W124; the W123 central doorlock system is connected with the engines' vacuum system, the W124 has a separate system for the central doorlock.

The W123 has (in general) more problems with the vacuum locking system as the W124...

what is yours?

__________________
1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)

It always helps us to help you better if you specify the exact model. I will proceed under the assumption that it is a 123 car because you eluded to the vacuum pump shutting off the engine. On the 124 the locks are operated by an electric vacuum pump.

On the 123 it is a very simple process to troubleshoot. Start at the drivers door. Remove the panel and substitute the vacuum supply with the handheld vacuum pump. From the drivers door you will either go to the drivers side rear door or to the passenger side. When you get to the passenger side don't forget the gas tank door and trunk latch that are downstream from there. Just substitute the pump for the supply line until you find the leak.

The good news is that with just a little care, you can remove and replace the door panels on these cars with no damage.

Good luck,

MBenz,

My 300D is a W123. But nevertheless, it sure is "speedy". Where can I get this hand held vacuum pump? Any idea how much a (good) shop would charge to repair the locking system? I'd rather save the $ and do it myself, but with school and all... it's hard to find time, but I'll survive.

I'd definitely do it yourself... I am VERY new at working with my 240D and I just fixed mine by playing around with it on the weekend... The shops in the Bay Area told me between 200 and 500 dollars (all labor). The parts for the diaphram pumps run about $30 a piece. BIG SAVINGS!

My problem: a rip in the rubber diaphram in the rear passanger door. Although my system works great now (with the exception of the Cruise Control)... members of the forum have suggested that the others are not that far behind.

Question? Should the vacum valve in the drivers door make a hissing noise? I've noticed this and am unsure if this an intentional design.

SB
____________-
1981 240D, (144K)

Mine used to hiss a lot. You can adjust the vacuum valve by loosening the two screws that hold it to the door and slide it to the left or right. I slid it to the left and the hissing was reduced.

__________________
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

You say the other three door locks don't work. Does the fuel tank cover lock and the trunk lock work or not. If not, I would strongly suggest that you check out the distribution switch which is behind the driver door panel. It does not sound as if you have a slow leak somewhere else. It is the black horizontal tube near the lock with three tubes connected. Someone else mentioned slightl;y repositioning this to reduce hissing. Same advice goes to seeing if you can get it to operate satisfactorily. Last time I bought one of these new it was about $30, probably more now. The 123 service manual has a good section on the vacuum locking system. Haynes has little. I got a very good vacuum pump at Sears for $39. All I needed for this tracing. Alternatively, the MightyVac availavble at auto stores should do the trick. Very useful tools, either/both.

Whaile you are at all this, I strongly suggest putting two small air/vacuum filters into the system under the hood. these will fill with engine oil if you get a leak at the vacuum pump or the shutoff device, thus saving you Big Bucks replacing all the rubber and cleaning out the tubes. Not to mention the ignition switch! There were articles in Star several years back about these filters. I installed them accordingly, and within two weeks one filed indicating pump failure. Two weeks later the other filled, indicating shuoff device failure. I was very, very lucky to have caught the failures this way before the oil fouled everything.

__________________
Douglas
1959 M-B 220S cabriolet

DB,
Where can one find these filters and how expensive are they? Thanks for the tip!!

SB

The filters (strainers, in M-B parlance) are available from any M-B dealer or other M-B parts source: 000-078-06-56. About $3 each. For 123 models (240D and 300D you need two. (I don't know how many are appropriate for the SD models of the same period. Perhaps others have comments there.) Also, they look exactly like a Fram fuel filter I saw at a parts store but without the M-B part number. I don't recall the Fram number. Do you need reference to the Star magazine articles touting these devices? As I said before, they saved my butt, not to mention saving me Big Bucks in repairs by allowing me to observe the failures before they shot oil into the entire vacuum system. Essentially what they do is slow down the oil migration long enough for you to see it happening by noticing the filter fill with oil. When one fills with oil, immediately, read immediately, get with the program and repair the failed device, be it the vacuum pump or the shut-off device. When the filters remain clear, no failure is indicated. Let us know how this works for you.

__________________
Douglas
1959 M-B 220S cabriolet

For kicks and giggles I decided to llok at my CD manual for my 1991 124 and in the Vacuum Line Roting section for the car it list a "filter" right at the top of the vacuum pump. I think that later on I may open mine up and see what is going on with mine. No trouble to report, but I like to stay well informed of the car.
ARI

The reason why the drivers door works, and not the other three doors, is because the drivers door is being unlocked mechanically, while the other doors are supposed to unlock using vacuum. (I would imagine that the fuel door, and the trunk aren't unlocking either).
-Larry

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

My 81 300 sd has an electric vacum pump in the spare tire well that seems to operate the door locks it works fine but can find no mention of it in any manual?
William Rogers...........

Douglas,

I know that the vacuum pump can fail and throw oil. But I didn't know that the shutoff device can also throw out oil if it fails. If that is the case then I would need to place a vacuum filter on the main vacuum line just before the vacuum lines split off into the passenger compartment. The other filter will have to be installed just before the shutoff line for the engine. Correct me if I'm wrong.
Thanks for the advice.

Douglas,
If you had the article references to the Star Magazine article on the filters could you please pass them on. The MB parts place I go to had no idea what these filters were. I took them to the website to give them the part number... he said he may order one for himself just to see what it looks like.

SB