Bimmerfest - BMW Forums - View Single Post - Got the 1.2 bar expansion tank cap from German Auto Solutions
View Single Post
Old 08-04-2013, 01:03 PM
gary@germanautosolutions's Avatar
gary@germanautosolutions gary@germanautosolutions is offline
'Fest Sponsor
Location: Grand Rapids, Michigan
Join Date: Jul 2010
Posts: 425
Mein Auto: E39 528i, E60 M5
I thought that as the coolant was heated, it "expanded" and moved from cooling system (radiator) to the expansion tank. After the car is stopped (cools), coolant is drawn back into the radiator.
This is how almost all US manufactured cars work, and I think it is the simplest and therefor best way to do things. In this method the expansion tank is not pressuerized and has an extremely low failure rate. In most European cars the expansion tank runs at full system pressure and actually has constant coolant flow through it. That is why there is such a high failure rate in this type of system. The problem is compounded by BMW's choice of a 2.0 bar venting pressure for these cars.


"I'm a little rascal on my Little Rascal"
- unknown
Reply With Quote