I recently had a problem with my driver's side door lock on my 88 300e. I was too lazy at the time to investigate myself, so I dropped it off at the dealer for inspection. They call me, and inform me that my lock cylinder, and the vacuum operated locking mechanism was bad. I figured I could find that lock mechanism (sorry, I forgot what it was called) elsewhere for less than the 350. that they wanted. I did, however, buy the lock cylinder. 375.00. Winter approached, and I decided to put the whole project off until spring. As I finally completed my repair, it turns out that NEITHER were bad, and I simply had to replace my door latch. (30. at a junkyard). I'm so pissed for wasting sooo much money on that stupid cylinder. Not to mention 125.00 for the "diagnosis"!