Oh, so that's how it's supposed to shift! - PeachParts Mercedes-Benz Forum

Ether · #1 05-30-2009, 08:56 PM

What a difference it makes when you finally get vacuum to the tranny!

After driving my SDL around for the last month or so with each shift feeling like a deranged dwarf hammering on the differential, I figured it was well past time to attack the problem.

I'm chagrined to say that after 8 years and 5 different diesel cars I finally got around to buying a Mityvac. My biggest fear was allayed when a check of the Vacuum Pump showed a nice strong 23" hg. It then took me all of about 30 seconds to determine I had zero vacuum coming out of the vacuum amplifier feeding the transmission.

Obviously a big leak somewhere and actually I found 2. Disconnecting the lines to the vacuum transducers for the EGR valve and the recirculating air valve and plugging the 2 outlets on the 5 way that feeds them had a couple of positive results.

I now have vacuum to the transmission and my shifts are for the most part silky smooth. Occasionally the 1st to 2nd shift will be a bit firm but otherwise the shifts are smooooth. (Disclaimer: I don't yet know if I have "proper" vacuum to the tranny yet, just that I have some where before there was none)

The other positive is that I now have air blowing from my center vents. Before most of the air was coming out of the defrost vents regardless of the selection on the panel. Apparently disconnecting the recirculating air valve transducer relaxed the defroster flap?

I obviously have more troubleshooting to perform to get all working properly again but for now I'm happy to driving around with smooth shifts and cold air blowing on my face.

Bio300TDTdriver · #2 05-30-2009, 09:03 PM

Quote:

Originally Posted by Ether

Apparently disconnecting the recirculating air valve transducer relaxed the defroster flap?

Or now that you have restored vacuum to the HVAC system it is working properly. The default position is defrost when no vacuum is present.

Glad you have vacuum to your transmission and heat controls.

Ether · #3 05-30-2009, 10:24 PM

Quote:

Originally Posted by Bio300TDTdriver

Or now that you have restored vacuum to the HVAC system it is working properly. The default position is defrost when no vacuum is present.

Looking at the vacuum diagram there are 3 hoses that head in to the cabin, two labeled a (Ventilation to passenger compartment) and one labeled c (other ancillaries) and I assume one or more of those is the vacuum supply for the flap pods.

Regardless, they all were being starved of vacuum prior to me disconnecting the EGR junk.