[valiant67]

If the seal on the back of master cylinder is bad brake fluid can be sucked into the power brake booster by the vacuum. It may even end hip bread by the engine.

 

[valiant67]

Yes, stupid auto correct and me not catching it. The vacuum can draw it into the engine where it is consumed and burnt. If it is leaking at the rear of the master cylinder it can eventually deteriorate the [SIZE=10.5pt]diaphragm [/SIZE]in the booster or rot out the booster case causing a loss of power brake assist. Or you may notice that you sometimes hear a vacuum leak when pressing the brake pedal.