From the photo, I thought you just broke the rubber connector, not the check valve. Did you break the nipple off the check valve? If it's the yellow one with only one connection on the engine side and two connections on the firewall side, it's the line that feeds the door locks. This appears to bee the correct one:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1CQ0J3JZ41VP12JTNA&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1984&product=O4040-16683&application=000024045

You may want to call Phil to make sure.