Scenario: You park your car at Pep Boys but forget your wallet and go back to the car to get it. Its locked......so you unlock it, get your wallet , and then lock the car again. All this without running the car or starting it to recharge the engine vacuum.
While in Pep Boys, you notice you forgot the part u are trying to match, so you go out into the parking lot ONCE MORE and unlock/lock the car.
How many times can you do this without starting the car to recharge your vacuum tank?
All I can manage is 1.7 (sometimes 1, sometimes 2). Can anyone do better? Does anyone remember what their new car did? In a perfectlly sealed vacuum system, u should be able to do this infinite times...

In my 300CD with a used passenger door actuator and a new primary vacuum valve (on the drivers door) I can lock and unlock about 4 sometimes 5 times before the vacuum is gone.

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'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
'83 300D Turbo 220k (Orient Red) - WVO - Wifes daily driver

I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.

Interesting question. I just checked.
300CD - all original parts: 8 times (counting an unlock/lock cycle as 1 and not 2)
240D - gone with gf. Will check and post results when it returns...


7 on the 240D.

A finite amount of vacuum will not provide infinite action...

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1982 Mercedes-Benz 300CD
1982 Mercedes-Benz 240D - stick

Usually about 4 to 6 times, depending on temperature and humidity...

Normally I can get 6-8 times, the last couple times the locks are really slow. Was your ACC turned off? I think if anything is on when you shut the car down it closes some of the flaps and you lose some vacuum there.

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k

on my w123, 0 on unlocking, and sometimes they will all lock immediatly after shutting engine down! my w201 vacume locking works perfect all the time thgouh

6 to 8 times for my 240D.

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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride.

'13 Chrysler 200 Touring Candy Red. Grandma's ride.

Age and cunning will always over come youth and vigor.

Till the battery dies. Electric vac pump.

And without my keys at that, press button, beep beep, doors lock, repeat..

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

Eight.

at least 5 on my 85 300TD-T. I never tried to get it to not work.

Well I'd think that when brand new the system is perfectly sealed, yet the MB Service Manuals state that you should be able to do it only six times I believe.

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1999 Mercedes-Benz S600, 103K miles - garage queen
1988 Mercedes-Benz 560SEL, 89K miles - daily driver
2007 Hyundai Sonata Limited, 31K - daily driver

Our 78 300D will go six times if done right away. Wait 2-3 days then only 2 times.
My 1985 300D will only lock, not unlock and even then only sometimes and the trunk and gas cap never.

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1959 Gravely LI, 1963 Gravely L8, 1973 Gravely C12
1982 380SL
1978 450 SEL 6.9 euro restoration at 63% and climbing
1987 300 D
2005 CDI European Delivery
2006 CDI Handed down to daughter
2007 GL CDI. Wifes

(1980 300TD) I tried this a few months ago and got 7 or 8 cycles. But this week I developed a severe vacuum problem. Hard braking, engine won't shut off with key, locks don't work, and at the same time, a lot of black oil shows up in the air filter canister ( Paper type filter). Haven't found a leak yet. Could these all add up to vacuum pump failure?

On the topic of holding vacuum, I can shut down my 300sd (yes I know the locks don't count here) but say I shut it off the previous night, or way early in the day then drive it again at night, well, I put in my key and go to the glow stage, and I can hear all the flaps move around as soon as the climate control is given power, but the engine is still off/glowing at this point. So in order for those flaps to move when I glow it means that the car has been holding a vacuum for all that time correct? I have even tried then changing the climate control setting a couple times (with engine still off) and I hear all the flaps continue to move how they should and would if it was running. So my vacuum system must still be pretty tight....I know it had stuff done to it at some point, several of the lines and conectors are definatley not original. My flaps don't move till the car has started if it has been more than a couple days since it last ran, so I assume by that point the vacuum has faded away.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Is this with the later models that the trunk and gas cap work on vacuum?

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).