In my E320 (I weep silent tears of loss), I accidentally broke a connector that was on the driver's side near the firewall. It wasn't completely severed but leaked so badly that it couldn't move the climate controls. I went over the whole engine compartment knowing I must have done it but couldn't find the dang leak. My kid came out and heard the very feint hissing (I never did) and pointed right to it.

I throw that in and add my vote with the other folks' above -- post it in diesel. Those guys have seen it all.