Originally Posted by Mark DiSilvestro

My brother's preferred method of auto repair.

I can think of several of my own oops, however one of the less painfull, but more entertaining ones happened many years ago, when me and my best friend from high-school volunteered to flush the cooling system on his older brother's '74 Peugeot 504 sedan.
I carefully attached the flush-tee to a convenient 'heater-hose', connected the garden-hose, turned on the water, then proceeded to wait awhile, wondering why the old antifreeze wasn't gushing from the radiator. After about 5 minutes, we noticed a stream of fresh water pouring from the tailpipe!
That's when we learned something about air-injection emissions equipment, and how it was somehow connected to the exhaust system.
After splicing that 'heater-hose', we tried to start the car. It first cranked very slowly, then sped up and eventually fired, blowing a 5-gallon torrent of water out the tailpipe like a fire-hose.
We finally got the antifreeze changed, and there was no extra charge for flushing the exhaust system!

Happy Motoring, Mark