W202 Vacuum Leak-Climate Control Problem
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Joined: Sep 2002
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W202 Vacuum Leak-Climate Control Problem
My '96 C280 has what appears to be a somewhat common problem with the HVAC system, but I haven't found any suggestions on where the problem is likely to be.
The symptoms include the center dash vents turning themselves off and on, whistling of air as this happens, inability to direct air flow to the floor vents only and the vacuum pump in the trunk running way too much. This strikes me as a vacuum leak, but I don't know where to start looking. Is there a place where the leak is most likely to be occurring? The door locks and other systems seem to be operating properly.
(See https://mbworld.org/forums/showthrea...acuum+Question for one of the threads.)
Any help with this is greatly appreciated.
The symptoms include the center dash vents turning themselves off and on, whistling of air as this happens, inability to direct air flow to the floor vents only and the vacuum pump in the trunk running way too much. This strikes me as a vacuum leak, but I don't know where to start looking. Is there a place where the leak is most likely to be occurring? The door locks and other systems seem to be operating properly.
(See https://mbworld.org/forums/showthrea...acuum+Question for one of the threads.)
Any help with this is greatly appreciated.
Senior Member
Joined: Apr 2002
Posts: 333
Likes: 0
From: NYC
red bicycle
Hey,
It's the PSE pump...mine is making a slight droning noise...but everything works fine. I've had it replaced before...a month after the car went off warranty, the rear defroster stopped working. The part was $1000, but the dealer did the work for free (considering it was just off warranty).
Check out this thread: https://mbworld.org/forums/showthrea...threadid=12996
From Patrick: "Yep, it is the PSE (Pneumatische SteuerEinheit), a sort of vacuum pump (however it also has electric/electronic functions). It is normal when you here it while locking or unlocking the car. When you here it more and/or longer than before you may have a leak. When you hear it while driving, it must be that air intake manifold pressure becomes too low. Under 300mBar (I do not know how much that is in American values, PSi's or whatever,...) the PSE "helps" to maintain all vacuum controlled things."
It's the PSE pump...mine is making a slight droning noise...but everything works fine. I've had it replaced before...a month after the car went off warranty, the rear defroster stopped working. The part was $1000, but the dealer did the work for free (considering it was just off warranty).
Check out this thread: https://mbworld.org/forums/showthrea...threadid=12996
From Patrick: "Yep, it is the PSE (Pneumatische SteuerEinheit), a sort of vacuum pump (however it also has electric/electronic functions). It is normal when you here it while locking or unlocking the car. When you here it more and/or longer than before you may have a leak. When you hear it while driving, it must be that air intake manifold pressure becomes too low. Under 300mBar (I do not know how much that is in American values, PSi's or whatever,...) the PSE "helps" to maintain all vacuum controlled things."
