Vacuum leak again

[benzboy]

Hey guys, I seem to plauged with these damn things, I can hear it from drivers vent, a slight hissing, which goes away as soon as I accelerate, idle is slightly lumpy at times, and the rear headrests take forever to go down, anyone have any idea where it might be if I can hear it from vert.... and if its possible to get to without destroying car.

Cheers
Tom

[1995c280]

my first guess would be to check the vacuum line for the head rests if they are slow to go down. when you press the release buttom for them on your car, they should fall down immediately. the vacuum line for them connects under your intake manafold. i believe it is under the 3rd or 4th cylinder. start from the front and count the humps on the manafold. then grab a mirror and a light. look under the intake manafold for a single (clear/white) vacuum line that should be connected onto a nipple from the manafold. this line gets knocked off all the time on the I6 engine when people change the oil filter in the back. it is routed right around the oil filter housing.

not saying this is your idle or hissing noise but it could probably be the problem with your headrests, u never know! good luck and update us!

Jason

[1badamg]

U check lines going to brake booster?

[NISMOPOWERED]

It sounds like one for HVAC system under the dash. Start the car and start looking under the dash. Good luck.

[DRM]

Hey,

It looks like I have something similar, the last out of the ordinary thing that happened before I heard this noise was that I went over a speed bump and hit something, I don't use my air conditioning that much so I don't know if this caused the noise or if it was something else.

But when I put the air con on settings 1 and 2 you can't really hear it at all, number 3 you can hear it a little but 4 and 5 it is pretty loud. And it comes from the left passenger side air bag / air vent area.

Here is a recording from the left passenger air vent:

http://www.nowupload.com?16467

The difference in the sound recording around half way is me opening the center vents but the recording is still from the open left passenger air vent with the air con on full.

[benzboy]

Man, this is a pretty old thread, I dont even own my C280 anymore.

Anyway, what it was and I have had the same issue with my C36 was the vacuum headlight adjustor dial, one of the tubes had come loose of the back so I just fiddled with it a bit and it stopped completely.

[DRM]

Hmm okay, well my level adjusting vacuum leads aren't hooked up to the headlights any more as I have crystal clears in there and the connectors don't fit on. They are just lying there not connected to anything, would this be causing the noise near the air bag / left vent?

[benzboy]

Quite possibly, might be an idea to block off those hoses

[DRM]

Oh okay, what do I block them with?

[benzboy]

Hmm... a plug of silicon would probably be ok, as you could probably unblock it if need be

[DRM]

okay cool, just the last thing I want is stuff being sucked back into the vacuum system lol.

[benzboy]

Yeah that would be a bad thing, haha