I have a 1994 C280. I tried the search tool but I need some education before I can use what it pulls up.

1. For the last month I've heard what I think is the vacuum pump cycling every 30 seconds or so.
2. Now it is cycling every 10 seconds or so.
3. I have no issues with anything vacuum related (locks, etc) except for controlling the flapper on the center vents for A/C.

Questions:
-- Is this coincidence or does it sound like my vac pump is cycling, I suppose because it is losing vacuum due to a leak somewhere?
-- Why is it affecting one thing but not another?
-- Is the vac pump somewhere in the vicinity of the back seat?
-- What do I do next?

Thanks mucho.

__________________
1994 C280, dark green metallic
105k miles

1991 190E 2.6, Black
191,500 miles
(sold to another forum member)

2003 Chevy Tahoe LT, Redfire Metallic
105k miles

1989 Mustang GT Cobra Convertible
43k miles

The CL pump is designed to HELP the engine vacuum supply for the A/C system.

You most likely have a vacuum leak in the a/c system & YOU will burn out the CL pump if it runs too much.

FIND & fix (or block off) the leaking vacuum system issue in the a/c system,

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Can I access the primary points in the trunk and behind the glove box? If so, what would be the first things to check (and/or color of vac tubes)?

Thanks

__________________
1994 C280, dark green metallic
105k miles

1991 190E 2.6, Black
191,500 miles
(sold to another forum member)

2003 Chevy Tahoe LT, Redfire Metallic
105k miles

1989 Mustang GT Cobra Convertible
43k miles

The A/C vacuum control valve block is beneath the under dash panel on the passenger side.

Here is a link to the vacuum system vacuum line diagrams Help

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

It sucks.

__________________
600SEL '91
300E 4Matic '88
240D '83
280SE '77
350SE '73
The most complex systems can fail in the simplest way.
Contra verbosus noli contendere verbis, sermo datur cunctis, animi sapientia paucis.

i don't believe in the lord! He's never bought me a Mercedes Benz.