Vacuum locking system

[Chigham]

So I'm new this this forum .  I own a
1979 6.9 450 SEL that I did a frame off
The only thing not working properly on
Vehicle is the vacuum locking system

I've been told that it better to convert to
Electrical system .  Less problems vs the
Vacuum locking system .

Does anyone have any thoughts or expertise
In this matter ?  Much appreciated

[ptashek]

Invest some time into identifying, and getting rid of leaks.

Replace all lock actuator diaphragms on principle. Same with rubber tubing connectors. Make sure all check valves are in working order. Replace rear and front vacuum reservoir grommets where the hard line enters the reservoir. Replace vacuum valves in heating system, or at least check for leaks. Check the master lock valve, it's a common source of leaks.

Do one thing at a time, then vacuum test the whole system. If it still leaks, move to the next item on the list. Once leak free, the system works perfectly fine.

[daantjie]

Indeed yes converting the system to electric would be a mistake in my opinion. It is part of what makes a 116 a 116 and once sorted the system actually works very well.

[raueda1]

Invest some time into identifying, and getting rid of leaks.

Replace all lock actuator diaphragms on principle. Same with rubber tubing connectors. Make sure all check valves are in working order. Replace rear and front vacuum reservoir grommets where the hard line enters the reservoir. Replace vacuum valves in heating system, or at least check for leaks. Check the master lock valve, it's a common source of leaks.

Do one thing at a time, then vacuum test the whole system. If it still leaks, move to the next item on the list. Once leak free, the system works perfectly fine.

^^^^THIS.  And to elaborate a little, it's a good practice to use a little silicone grease on the rubber fittings.  It makes tubing easier to install and contributes to an even better seal IMO. The check valves are cheap and readily available.  And pay special attention to the master lock valve.  Mine failed and the brand new replacement turned out to be not good.  !!!???  The supplier sent a replacement and all was fine.  However, the positioning/alignment with the locking lever is critical. Even a tiny bit off and it will appear to leak even if valve is good.  A secondary benefit is that you can clean and lube window mechanism while door is open, though you probably did that during your frame-off. 

And I agree with Daniel FWIW, keep it stock.  Installing electric would end up being a bigger job than just fixing it. And please post some pix of your project!  Everybody here loves that kind of thing.  Cheers,

[Neil4speed]

If you took that much effort to do an in-depth restoration, I would 100% take the effort to sort the vacuum system. Not to say it is simple, but it is fixable generally speaking.

Also share some pictures!! We want to see your car

[mrkozzy]

Then there's the other side of the coin.
Love my 116 but got tired of the vacuum locking system failing soon after it was fixed, time and time again.
 Cannot count the amount of times I removed the door trims looking for the vulnerable leak, or searching the system under and through the body work.
Had an electric system fitted over 10 years ago and it only failed once. That was 2 months ago when the original battery in the remote failed. Changed the battery and voila, working again.
My weekends are meant to be for driving and enjoyment in my car NOT spend chasing another vacuum system failure.