Just experienced a problem with my rear drum brakes on my tdi 75. 4 weeks ago while driving to work I got stuck in a deep puddle full width of the road. Car stopped dead about 3/4 the way through the puddle. Water started to come in the bottom of the doors!!! Engine restarted and managed to drive out and continued until the road was blocked by a landslip so went back home. Over the next three weeks kept feeling something not right with the rear brakes, they would tend to stick on when pulling off and not feel right. Well Friday the car went into the garage to see what the issue was. Turns out one slave cylinder was completely seized with both pistons corroded and the other had one piston seized and the other not far off. New slave cylinders fitted and shoes fully checked and car is now back to normal. The moral of this tale is if the drums have been wet take them off and check / clean / replace the cylinders.