Aramis001

I just bought a 1994 740 il. The radiator, water pump and the fan looked brand new. Not even a dust grain on them. Less than two weeks driving it, I developed a leak in the radiator. The leak is right under the upper hose entrance from a round plastic extrusion. Looks like it is a safety pop-out. Seemed the pressure behind the closed thermostat was forcing the plastic open further. Few days later, my water pump started making grinding noise. In less than one hour the pump shattered bearing and seals. Since all above parts looked brand new, can anybody advise if the problem may be related to other malfunctioning other than bad luck. The car was not in an accident. I checked with Carfax and all seem to be OK.

bmw740i

I also had a similar problem. My housing on the size of the upper hose connector on the radiatior developed a 3 inch long rupture and we could not understand why. Anyway checked had the radiator replaced but could not bleed the system properly. Eventually checked the Thermostat and upon testing realised it was not opening. This in turn caused the build up of high pressure, forcing the radiator to blow.

Obviously this must be some form of design flaw in the Thermostat as the garage had encountered this as a frequent problem. Surprisingly enough no recall or information available from BMW!!!

Aramis001

I assumed the radiator issue was related to the pressure, specially when I noticed the thermostat on the car had broken arms. (arms which hold the spring ). I bought the car from Florida (ebay) a month ago and changed the thermostat since the car was not warming up. The radiator problem developed after the new thermostat was installed.
I now have modified the new thermostat. I made a 1/8 inch hole in the blocking plate. This allows limited water flow while the thermostat is closed. The hole is large enough to reduce the pressure build-up, it however is not large enough to damper the correct operating temperature of the car. I still am puzzled by the water pump problem. Anybody had similar experience?