I'm a recent owner of a '89 535ia E34/M30. Cracked left radiator tank beginning of overheating probs. Had it replaced. I thoroughly cleaned radiator (in/out), seems to be in good shape. Lasted several days before frequent overheating. I was somewhat pleased to learn on this sight that this was merely a right of passage for a BMW (Bring More Water)owner. Unfortunately working outside in 15F temps night after night is getting silly. I had poor coolant so flushed many times. I learned how difficult bleeding was so I've tried every way about a dozen times. I boiled the old thermostat and it didnt seem to open so I replaced it, nothing. I opened up the water pump sure I'd find more brittle plastic fins cracked and loose on their spindle. But found solid steel instead. I've tested the fan clutch, seems right on (took considerable effort to stop). I have disconnected most hoses expecting to find coagulated coolant, nothing. Every step brings me closer to my fear of a blown head gasket or cracked head. There has never been any sign of H20 in the oil nore in the coolant, although I've gone through many gallons of coolant. The tail pipe spews condensation but what doesn't up here? Every time I bleed the system I add more coolant yet see no leaks. The heater worked intermittantly throughout this problem, either 1-3 zones or none. Now I get 0 heat output. Coolant bubbles out the reservoir tank if I leave the cap off (to assist in bleeding). I'm still using the recalled cap but have left it off, tightened it down and everything in between, I can't imagine that is it. My auxilary fan doesn't appear to come on but I wouldn't think that is it either. My friend who took my perfectly dependable Honda on trade keeps suggesting I take it to the dealer. However he is now selling his '89 735ia after having it to the dealer about 7-8 times for overheating. They have comped him several thousand dollars in labor but have also told him they don't ever want to see the car again. Any suggestions? I'm stumped.