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84W123DT 02-12-2004 02:17 AM

DOOR LOCKS - vacuum loss when it's COLD outside.
Yes gentlemen, I've done a search.

And as suggested by this Forum, I've replaced the "yellow" check valve by the brake booster and all the 3-way and 4-way rubber fittings in the engine compartment and still, here's my problem:

18* C (about 68* F) holds vacuum enough that you can lock and unlock the doors 6 to 8 times, fine. It functions the way it should be.

5* C (about 40* F) complete vacuum loss after about 10 minutes.

There is a leak somewhere but I can not find it!!:mad: Where else should I hook up the Mity Vac to test without removing the interior door panels?

Your HELP is appreciated.

wolf_walker 02-12-2004 07:58 AM

Something bothersome I noticed about my mityvac, is it will now and then get a piece of crud in it and leak down itself. Kink the hose and make sure it holds tight now and then.

Temp related, hmm, rubber gets more brittle in lower temps, could be a small rip or puncture in a seam on one of the vacuum actuators that is only in evidence in cold weather.

They do odd things, I just replaced a fuel flap actuator that was air tight either closed or open, but about half way it would sit there and leak vacuum for a bit till it closed or opened completly.

edit: You can test those actuators without pulling the door panels if you can figure out which vac line there on, which requires pulling the floor mats, carpet and maybe a bit of moulding. I'm not familier enough that I can tell you exactly which is which, but there a bunch more 3 and 4 way splits in there under the carpet you can tap and check. Both on drivers and pass side. The trunk and fuel door are on the same circuit fed from the passenger side.

psfred 02-12-2004 02:28 PM

Shrinking rubber.

See if the locks will hold without the vac reservoir (under driver's front fender or in rear bumper). If so, replace the rubber fittings on the tank. Also check for cracks.

If it still leaks off, you will have to do it the hard way, one door at a time.


pberku 02-12-2004 03:01 PM

Typically, door vacuum leaks occur where the vacuum hose runs between the body of the car and a door hinge. The frequent opening and closing of the doors causes the hose to crack at that point. This most often occurs on the driver side door as its the one that is opened and closed most often.

Remove the rubber tube between the body of the car and the door hinge at each the doors and examine the vacuum hose closely. Sometimes you can also hear the distinctive "Hiss" of vacuum loss. You will most likely find that its cracked there

84W123DT 02-16-2004 01:30 AM

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Where is the vacuum supply tank #3 located in 1984 MB300DT?

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