My money is on the monovalve at almost any odds.

You can get a repair kit for a little over $30 and it takes only about five or ten minutes to replace.

Good luck,

------------------
Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles