W140 Front Duovalve Seal Kit? - PeachParts Mercedes-Benz Forum

tinypanzer · #1 04-10-2017, 10:41 PM

Hello all,

I did quite a bit of searching here, and apart from posts with dead links, I couldn't find any discussion of doing the seals on the FRONT duovalve on a w140. On my 97 S420, I have intermittent failure of the valve which causes the climate control to suddenly start blowing quite hot. Examining the valve, I noticed that it had been weeping slightly for a long time, and that water and coolant had corroded the electrical connector quite badly, so much so that I can't even get the plug off for fear of breaking the thing with too much force.

I cleaned it up and sprayed some contact cleaner into the plug, and it got a little better, but it still fails and blows hot eventually. I am reasonably sure that if I can get the valves out and safely get that connector off, I can clean it all up and re-seal it and be on my merry way... Certainly seems worth the bother over a nearly $500 part.

Does anyone know of a source for the seals? So far all I can find are dead links, and even then mostly discussion of the rear heat not the front.

I'd love to do a writeup on resealing these if parts are obtainable, so any leads would be awesome.

Two pictures attached, first is corrosion before I cleaned everything up, second is afterwards from above. I think I need to remove the 6 screws holding the valves to the body and they will lift up connector and all. The seals are ostensibly right underneath, but I don't really know as of yet. I imagine there will be O-rings and stuff too...

tinypanzer · #2 04-11-2017, 07:02 PM

After much searching, I finally found something on fleabay. It appears to be made in Taiwan by a company (I don't read Chinese) who makes a lot of replacement rubber parts for w140 and other MBs.

W140 Heater control Valve Repair Kit OEM Mercedes Benz W140 | eBay

Here's a pic from the auction, for when the auction link eventually dies.

Anyone used one of these before? Any U.S. suppliers of this, such as here on Pelican? Can't even find the valve in the parts lookup, search engine could use some help...