Brake booster one way check valve?

[canada karl]

Can someone confirm that the white side of the check valve is on the booster side? Thx Karl

[HB528i]

See pic

[canada karl]

Thanks for the pic. Can you think of any reason why I would be getting a hard brake pedal and poor braking? Car slows down but you have to really press down on the pedal.Other evidence is brownish brake fluid in the MC. I may try bleeding the brakes and installing fresh fluid to see if that helps. The car has been sitting for a long time.I hope it's not the brake booster as I believe they are no longer available! What else could it be ?

[dutch]

I`d look into frozen calipers.