Another great trick to use especailly with allen head bolts that has been mentioned before-

Put some valve lapping compund on the allen and tap it back in again. The compound is gritty and takes up space helping to ensure a tighter fit.

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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)