@stevebuchanan posted:It might be best to not open the pressure control valve and only bleed at the calipers. There could be air trapped in the pressure control valve at this point. Maybe just gravity bleed the front calipers one at time and test the car again. Be careful to not let the reservoir run low. Bleed the bottom first and finish at the top bleeder.
If the problem still happens after bleeding as described above then maybe focus on the brake master cylinder. Its seals may be tired. One of the symptoms of bad seals in a master cylinder is needing to pump more than once to get pressure. Another symptom is fluid leaking out the back. There may be enough wiggle room to unbolt the master while leaving the brake lines connected and check for leaking fluid at the back.
It sounds like your shuttle valve is working correctly.
Thanks! In my understanding the master brake cylinder cannot be the cause - a failure there would not trigger the brake warning light, right? And I am not loosing brake fluid.
Looking forward to my next test drive, but the conditions here in Austria are not right for now.
best wishes.........Eugen