Passat TDI CRANK SHAFT Bolt

There's usually a square key between the crankshaft snout and pulley hub.

To get the bolt out, if it is broken off flush with the snout, fashion a way to hold a rather large nut on the end, heat the broken bolt with an acetylene torch for a few minutes, then use a wire-feed welder and weld to the bolt. Don't stop or take a break until the weld builds up and fills in the center of the nut. The goal is to get the bolt as hot as possible. The heat is going to be sucked out of it very quickly, and the weld won't penetrate if the bolt is not hot enough to melt. A propane torch won't work for this.

Once the center of the nut is filled in, wait about ten seconds, then dribble a little water on it to shock the bolt, then you can use a socket on the nut to remove the broken bolt.

I've used this trick for much smaller thermostat housing bolts. When those are threaded into aluminum, that removes the heat very quickly. I've already had to resort to doing this five or six times before the bolt came loose.

Dandy. At this point I think you can forget about welding a nut to the bolt.