Transmission Vacuum transducer (blue saucer) - PeachParts Mercedes-Benz Forum

GregZ · #1 11-17-2008, 07:02 PM

Hi All,

Another vacuum transducer/amplifier question ('85 300SD). Should the PRe port of the blue saucer be leak free? (again, if you connect a small pressure source or small vacuum to the PRE port of the saucer directly (disconnecting everything else connected to that port), should it be air tight?)

Thanks,

Greg

Jeremy5848 · #2 11-17-2008, 09:12 PM

I do not know from having actually made measurements but it stands to reason that it should not leak a lot because there is a long string of hoses and valves leading up to the saucer. If there is too big a leak, the pressure will drop off, like voltage drops when there is a big load and too-small wires. Also, since the pressure input is merely a signal that tells the saucer (in part) how much vacuum to give the transmission, there should not be much of a leak. Best way would be to hook up a Mityvac, pressurize the connection, and see how long it takes to drop off. Since the pressure port is on the bottom and hard to get at, I can't easily test mine.

GregZ · #3 11-17-2008, 09:41 PM

Jeremy: exactly my thoughts.

However, mine is not air tight (and it is not the connection but something inside the saucer) - it actually has a rather major leak. It'd be great if I knew it for sure though - 100% is better than 98%). Actually it is not too hard to test; the "vacuum" (pressure) hose coming from the ALDA can be disconnected at the ALDA and so the saucer's PRE port can be checked.