E39 brake master cylinder

[Rich8]

On the brake master cylinder on the E39's, there are 3 pressure outlets......one in front then one out each side towards the booster. Can anyone say exactly where each of these 3 lines go? what does each one do?

[rdl]

Two are pressure outlets. One is a pressure supply.
One line supplies pressure to the DSC/ABS valve block for the rear brakes. One line pressurizes the DSC/ABS block for the front brakes. One line comes from the charge pump to supply pressure to the front brake circuit when DSC is intervening for stability control while cornering. The charge pump is not activated for ABS.

The attached image shows the DSC hydraulic schematic. Note that the ASC+T master cylinder is different from the DSC m/c. I don't have ASC+T details handy and can't recall the differences off hand.

DSC5_7_HydraulicUnit.jpg

[Barrman]

That pressure supply line from the charge pump requires a check valve inside the master cylinder for the stability control system to function properly. I learned that lesson the hard way when I bought a new master off Amazon. Everything worked great until I hit 30 mph and the abs/dsc system did a self test by turning on the charge pump. No check valve means failed test and the trifecta of lights on the dash.

[Rich8]

Thanks, that's just what I wanted to know.