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  #1  
Old 12-07-2002, 08:13 PM
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Join Date: Jun 2001
Location: Madison, NJ
Posts: 117
driver door master valve - what indicates not working?

When I tie the mighty vac into the inline on the driver door master valve and pump the system in "lock" or "unlock" mode the door locks behave appropriately and hold a vacuum once done BUT when when I move master valve to the other position the vacuum drops down to zero and I have to pump it up all over again. Is the master valve supposed to hold vacuum during the transitions, too?

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Old 12-08-2002, 05:05 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
The vac will drop to 0 in the operating lines -- vac is applied then sealed -- when the other action is selected, the first line is vented.

If the vac in the supply side drops off with the key centered, replace the vac switch if adjusting the position (it has some back and forth adjustment) doesn't fix it, it is leaking. System must hold vac indefinitely when the key is centered.

Make sure the vac tank under the left front fender is holding vac, too -- the rubber gromet at the top where the vac line is connected goes bad and the vac leaks off. Just pumping down the supply line to the door itself and not the tank won't give you any reserve vac, just what is in the MitVac.

If the tank won't hold, you have your problem. If it does, check the switch.

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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Old 12-08-2002, 07:54 PM
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Location: Madison, NJ
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When I tie into the supply side of master valve, pump up to around 15 inches then slide valve from one side to the other the supply side vacuum drops to zero. Does that indicate a bad master valve?
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  #4  
Old 12-09-2002, 09:28 PM
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Location: Evansville, Indiana
Posts: 8,150
Sounds more like a leaking vac diaphrams, but you tested that, didn't you -- the red strip locks and holds vac, the green stripe line unlocks and hold vac?

If so, switch is leaking. Could be misadjusted, though.... it moves a little on the screws, and I suppose it could be out of position enough to vent the vac.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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