Hi guys, I had a leaking ABS Unit so I swapped with a 2nd hand one, supposedly taken from a car that was damaged in a barn roof collapse, so in working condition. I must say that before I noticed that my old unit was leaking, I swapped all disks and pads but very hard breaking remained tricky. Strangely, the previous leak was small and never let air in the system, that's why it was noticable only from under side. I did not have any lights on dashboard or error codes about braking. Anyway, I swapped the ABS units yesterday and it was tricky to bleed all air out with the traditionnal bleed procedure, but now the brake pedal is firm but the system remains under pressure, meaning everytime I touch the brake pedal, it brakes but the calipers don't open back totally, and quite quickly it becomes impossible to move unless I open the bleed valves on both sides to release some pressure. This release of pressure could to be done in both front wheels or both rear wheels, as the system is divided and linked (see picture attached). But the cure doesn't last : if I press 5 or 6 times, even slightly, it blocks back. I let the calipers bleeding valves open for an hour, hoping that remaining pressure would go away, but without success. Next Week-End I'll perform another bleeding using the AUTEL MS908 Pro from a friend, but I don't understand why this pressure problem happens, since the braking system should work even if the ABS Unit is faulty. Any idea or suggestions ?