2004 R53. After changing oil Thursday night, drove the next day extended distance and after first stop heard rattling noise, thinking it was timing chain tensioner associated, continued driving without much noise while driving. At the latter part of the day, engine got hot. Allowed vehicle to cool down in the garage when arriving home, found small amount of antifreeze under the car. Next morning car starts and sounds normal but shortly thereafter pegs hot temp at idle. What suggestions and options for diagnosis?

 

Supercharger is possibly gone OR water pump. In BMWs infinite glory they decided that bolting the waterpump directly to the SC was a good design decision. I had an aweful whine and my car would over heat at idle after a few min. Its possible yours is gone as well. I spent about 1100 between the pump/Remanufactured SC/Pully belt/belt tensioner/Idler pully(mine backed out driving down the road a few days before I was going to work on it). I did all the work myself and it was a pain.

Try bleeding out the coolant first(double check the overflow and fill to the MAX line if low). There are 2 bleeders, one right on the top of the radiator. Its plastic with a Phillips head slot in it. The 2nd is near the airbox, its hidden pretty well, uses I think a 10mm socket. You can usually follow one of the lines into the thermostat housing and see a bleeder there. Bleed both of those out and see if it helps, I highly doubt that its air in the system but who knows.

I have a feeling the pump is dead, or the chargers PTO gear is bad. You're description sounds identical what I went through. I drove through the whole winter with a bad gear in the SC, Luckly all my commute is highway and it only over heated a hand full of times.

 

Have you checked for proper engine cooling fan operation? That's always step 1 of overheating diagnostics.

 

Hi Guys. Thanks for the tips and info. I now have the car at Cincinnati Mini dealership and all they have found is the fan first stage is no operating do to a resistor but have to get new fan as it is all built in.They want to do a leak down test to the tune of another$200. I already have spent $300. getting it there and their initial diagnosis and that doe not explain anything about the diesel sound the car was making prior to overheating. I dont think another $200. is going to give me the right answers but I am supposed to call them back and let them know what to do. Thanks again for any tips