1981 300D

My locking system wasn't working at all...even with the engine running.

I've troubleshooted the door lock vacuum system and this is what I've found:

Lines and fittings are OK
Trunk actuator OK
Gas tank lock actuator OK
Vacuum reservoir OK
Vacuum switch in driver's door OK

Actuators in RF, RR, RL doors had cracks in the exterior rubber boot. I replaced them with fingers donated by a latex glove, glue and sewing thread. They won't hold vacuum too long but I went ahead and installed them to check. The locks are now working but with the engine running. A few seconds after is turned off...the locks are inoperative.

So...what are my alternatives to fix/replace those actuators? ************************ lists a kit @ 6 bucks each to fix them but they say that 4 of these are required.

One interesting thing happened. Before playing with the lock system...the cruise control was totally inoperative....however, when I replaced the lock actuators with the temporary repair...the cruise control began to work partially. It would accelerate the car when the lever is pushed up but it wouldn't keep the selected speed. I thought tha locking system was isolated from the rest of the vacuum system by means of a check valve at the firewall or something to that effect. Any clues??

Thank you.

You didn't say what car this was on, so things may be different. The older cars had single diaphram actuator (Actually 2 diaphrams one top and one bottom, but a single system) while others had dual diaphrams (2 upper, 2 lower). The singles can be rebuilt using the replacement rubbers you found at Perfromance. If you have singles, call Phil at PartShop and see if PartsShoip or FastLane can provide these rubbers. If you have the dual diaphrams you'll have to replace the entire acutator I believe.

The system will only hold vacuum after shut down once the system is completely sealed. I also believe your cruise is vacuum actuated and now that the system is partially closed you are gaining some function.

The cracks you found in the rubber were all on the top, weren't they?

__________________
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

Hi Mike,

My car is a 1981 300D. The cracked rubber boot is the only visible rubber component in the actuator. The actuator has 2 inlets for 2 hoses. I think the only way to know for sure how to replace/fix is with the chasis number which I don't have right now.

81 300D is a W123.

Did you take the actuators out of the door or inspect them in place? The upper hose and diaphram should be for the lock cycle and the lower hose and diaphram for the unlock. Sounds backwards, but when vacuum is applied to the upper section, the diaphram draws down, thus locking the door. Conversely, when vacuum is applied to the lower set, vacuum draws it up thus unlocking.

I think the actuators are held in by two 8mm nuts/bolts. You will have to disconnect the linkage rod that runs up to the knob, and remove that from the door as it is attached to the diaphram. It simply screws/unscrews to a nut held within the diaphram.

Some new actuators come with the linkage rod as part of the package, some don't and you have to reuse the old rod.

__________________
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

kefer,

Six bucks is the cheaper way to go. The replacement units run 50-75 ea! What part no did they give you? I have similar probs in mine. I have searched that site and could not find them. My cruise control is also inop. Thanks for the input