1983 240D manual transmission, manual climate control

In another thread, I describe the problem I was having with not being able to shut off the car unless the drivers door was locked (I clearly have a vacuum leak). I was able to "solve" the problem by disconnecting the vacuum lines to the driver's door (plain yellow) and the vacuum reservoir (yellow with grey stripe) and plugging the source. (If I only eliminate one line or the other, the problem persists.

Do I need the vacuum reservoir for anything other than the door locks? Or is it fine for it to be removed from the system? In particular, do the brakes in any way rely on the vacuum reservoir?

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

As I recall, yes the brakes are effected by the reservoir.

You need to test the door lock components with an auxilliary vac source and replace any leakers.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

I say it is only to hold a reserve for operating the locks with the engine off.

There is a check valve between the branch for the locks and tank (the yellow hoses) and the other vacuum consumers.

I further my point based on the 124. It does not have a vacuum tank and the door locks do not run off the engine vacuum. On a 124 only the engine systems and the ACC run off engine vacuum.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

My current configuration is that I've disconnected the check valve to which the two yellow hoses are connected and then plugged the line that was going into the check valve. Braking seems fine.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I'm interested in learning more about how this works. What is it about the location of the check valve that's significant? If I remember right, it flows easily downstream, but there would be some sort of cracking pressure to go the other way, is that correct?

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Searched and found this for you. all you need to know about the W123 vacuum System.

W123 Vacuum InterLock Diagram


Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

The 124s have an electric driven vacuum pump under the back seat for this purpose.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

the 124 has 2 or 3 vacuum reservoirs... two are in the fenders one is in the front near the headlights I think... not sure. I've totally dissassembled a 124 gasser, and they are everywhere on that car, probably for emissions stuff. not sure if the diesel variety have them... I've not taken a diesel 124 to bits yet...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

disconnecting your vacuum components should only be a "quick fix" for temporary relief of vacuum problems. IMHO.

It's so easy to find and fix vacuum problems in a w123 there's no reason to have to sacrifice functionality.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

That reservoir is solely for the door locks, so you can lock and unlock several times after the car has been turned off. The check valve should be upstream of the split for the door lock line and the reservoir line. This will allow the vacuum to move about the door lock system but not any other system. It should go main vacuum supply line, to the check valve, then a 3-way connector, then to the door lock line and reservoir line. It should look like this.

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Great clarification....thanks!

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Does anyone know if vaccum is req'd to start a 240d? Does the vacuum fuel shut off use the vac to switch off the fuel or to enable fuel flow? My 240 has just developed a reluctance to start first thing. Not temperature related, just hard on first start, tunrs over well, appears to have fuel at IP, just doesnt fire for ages. Wondering if the low vac at idle (10) is a factor....

Once it has been started once, it's easy to start for the rest of the day.....

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I choose to be happy, even when the Mercedes is being awkward, lol

Not required.

Off. The opposite would be a very poor design choice.

Your cold start problem could be due to leaky valves in the fuel pump, which allow fuel to flow back to the tank as the car sits idle. Or an air leak somewhere in the supply line or the hand pump.