The brakes on my 240D have been erratic recently, so this weekend I replaced the worn rotors and brake pads, flushed and replaced the brake fluid, and bled the brake lines. However, when I test-drove my car to check the brake function, I discovered that I had lost all vacuum assist from the brake vacuum booster. The brakes function, but require considerable effort before engaging.
I can also report that the fluid level in the front of the master cylinder reservoir was low, although an inspection indicated no leaks at the calipers, and that the fluid level had dropped since I checked it 300 miles ago.
I don't believe that my vacuum pump is defective, since my locks continue to work, and the engine still shuts off. Thus after consulting my manuals, I assume either the vacuum booster or the check valve is at fault. I've tested the booster per the manual--pumping and holding the brakes and starting the engine--and there is no movement in the pedal when the engine starts.
Are there other tests I can do before ordering a new booster? Is a used booster from Atlanta Stuttgart Auto Parts an option, or should I order a new one? Can anyone suggest a way to remove the check valve from the line coming from the vacuum pump? So far it has resisted even my most insistent efforts to remove the valve for testing.
Does anyone have any words of advice before I proceed? Thanks.