what was your most disasterous repair attempt?

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1996 E320
2000 C230 Kompressor
1988 190e 2.3 - 225K miles, owned for 7 years. I cannot say enough good things about this car. Very well built, even at 225 it ran like new.

This would have been a disaster if I cared even a whit about originality, but I don't so it's just amusing (to me, anyway):

The "automatic" antenna on my '72 350SL didn't work when I bought the car, so I bought a new Hirshwhatever, got out the workshop manual, and learned that I first had to remove the exhaust system, disconnect the parking brake underneath the car, then take off the driver's side kick panel (remember, in '72 the antenna was in the FRONT fender).

After reading the entire 32-step process, I thought "No way I'm gonna take off the exhaust to replace something in the left front fender!" I did take off the kick panel to see what I could see, but it it didn't look like you could even get to the antenna with the parking brake pedal in the way, so I put the panel back and rethought the whole thing.

I've always liked the look of the antenna in the rear fender better anyway, so I fired up the Sawzall (C) and mowed the old antenna down even with the fender. Not wanting it to rattle in there, I smeared a dollop of JB Weld (C) onto the the inside of the hole and pushed the antenna down and into the hardening epoxy. I'm good at fixing holes, so that was easy, and after I complete the new paint job, I'll put the new antenna in the left rear fender and be done with it.

These cars aren't that hard to work on - you just have to set your standards low and then work hard to live up to them. Someone in the future may refer to you as "the DPO," but the thing to remember is that the "P" stands for "Previous" - he's the DCO!