At some point in the near future I'd like to fix the central locking system on my 79 300sd, but for right now, I'd like to make it a manual system and take it out of the loop.

At the brake booster I see the yellow and yellow/grey line feed into a blue and light blue checkvalves. Can I just reverse the valves or plug with golf tees to make the system manual?

Will it work like any other manual system... or will it be hard, will their be resistance in turning the lock...like there is when I don't have the drivers door locked and the passenger locks won't budge until the driver door is locked?

I'm sick of telling people that have to wait for me to get out of the car and lock the drivers door so they can lock their side...and having to walk around and only being able to lock the two passenger doors after I've locked the driver door is a pain.

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1979 300sd 290K

You could open up the passenger side door panel and put a golf tee in the vac line and see if that helps. Then you will be on your way to finding out what is wrong and maybe fixing it. Who knows maybe the line came off over there. Check out the connections inside the driver's door as well while you have the other door panel off.

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If it ain't broke take it apart and find out why.

1983 300SD, 4 speed
1994 C280
1987 300TD wagon
1996 HD Road King

Ride in Peace Eric Peterson, Harley of Macon

I'm not really interested in removing the door panels at this time. When I do that I'll be dealing with my power window issues etc.

As I said earlier...I'm really interested in making them manual FOR NOW and wanted to see if I could do this under the hood. I would be doing this as a temporary fix. I have other more pressing projects to tackle before I do all my windows and door locks.

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1979 300sd 290K

I just did this to restore vacuum in my '81 (so now it finally turns off!). Just unplug the two yellow lines going through the firewall and you should be alright.

On mine, both lines were hooked to the same 3-way which made it even easier.

If you have a vacuum gage & pump, take ten minutes & check the lines coming off the master vacuum line to make sure they're not leaking. I had a bunch of leaks here but after replacing a couple of connectors it's factory-fresh.

Sorry forgot to add this; you've probably seen it already but if not it's a great place to start :
http://www.dieselgiant.com/mercedesvacuumtroubleshooting.htm

To answer the question, yes you can unplug the lines under the hood. Just make sure you plug the feed line running to the locking system, but leave the locking system up plugged so you can operate the locks manually.

Then, when you have time, start tracing the source of the leak. It is a good idea to check the rest of the system now though.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

So I plugged the lines with golf tees and found oil in the lines.

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1979 300sd 290K