Author Topic: Central Locking Questions  (Read 135 times)

ngruzevs

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Central Locking Questions
« on: 27 December 2019, 11:51 AM »
I've got some questions about the central locking on my 79 450SE, as it only seems to hold enough vacuum for 3 locks and unlocks after the car is stopped. Is this normal for a 40 year old W116?

I have tested elements of the system and have some other observations that may help

- If I don't lock the car, I still have vacuum for weeks, as I found out when working on passenger front door, disconnected the lines after a 2 weeks of car being stationary and heard a gush of air when removing lines

- If I don't lock the car, I can come back 24-48 hours later and successfully lock all doors

- Rear drivers door actuator seems to be a bit lazy compared to the other doors, even with vacuum this door is slower to lock and unlock than the other three doors.

- When I unlock the drivers door, there is a gush of air that emirates from the end of the master door actuator, it's audible to the point that you can hear it when the door trim is on

- Tested three vacuum lines in drives door y/r holds pressure, y/g holds pressure, but middle yellow line leaks very slowly

- Tested both blue one way valves in engine bay, both hold pressure.

Thanks in advance, keen to hear feedback

Nick

« Last Edit: 27 December 2019, 04:21 PM by ngruzevs »
1971 MK2 Jensen Interceptor
1979 W116 450SE
1987 W126 300SE
2007 Lexus LS460
2018 Hyundai i30N

ptashek

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Re: Central Locking Questions
« Reply #1 on: 27 December 2019, 02:29 PM »
My car holds vacuum for months on end, but it has every part of the vacuum system renewed and resealed.

Based on the description, I'd say the master central lock cylinder in your driver's door is leaking. Quite a common issue. They were still available new not long ago, but are NLA now. There are aftermarket ones from VDO for about $50. Search for A1168000473 (OEM) or 248049004001C (aftermarket VDO).

Another thing to check is the rear reservoir seal. It gets hard with age, and starts leaking around the hard-line.

Then there's the actuator membranes, which can develop cracks as they age, and all the rubber connector and junction pieces.
1993 "Pearl Blue" W124 280TE
1979 "Icon Gold" W116 450SE (history, resto)

ngruzevs

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Re: Central Locking Questions
« Reply #2 on: 29 December 2019, 06:25 PM »
Thanks for the feedback. I've ordered a new VDO master central lock cylinder and will replace all the actuator membranes (already replaced the four in rear door drivers side door). Although the rubbers looked ok, it's an easy task to replace.

Once I've changes master central lock cylinder and all actuators, I'll retest the whole system with a vacuum pump.
1971 MK2 Jensen Interceptor
1979 W116 450SE
1987 W126 300SE
2007 Lexus LS460
2018 Hyundai i30N