That makes sense. I think the problem may be that the other end of the poppit things that slide in there... those were broken. I was hoping they would still work with just the short part of the shaft to keep them in place but after taking the valve back out, it looks like they were rolling around in there. I'm going to try the "rivet fix" that I read about on another forum to replace those stems. Unfortunately, the spare valve I had for a normal W210 also had broken poppits. It seems that those parts would have worked had they been intact on my spare valve (just FYI for anyone trying to scavenge parts for a repair).

Thanks so much for the follow up. I'll post again as I work through this to hopefully share any further info for others coming across this in the future.

__________________
Search Mercedes forums and websites at http://www.everythingbenz.com