Originally Posted by
onehundred80
With the ignition OFF the pedal stops where I would expect it to stop and it does apply the brakes, you have to use more pressure as expected. Turn the ignition to the ON position and the pedal falls, the brakes and ABS work fine the pedal is hard and no feeling of sponginess. I think this is because the ABS valves are bypassed with no power going to them. If you see the hydraulic circuit schematic there are more lines than you would expect. I will add it if I can find it..
I know You have been strugling on that problem for a long time,but, did You had ocasion to compare this depressed pedal getting lower as soon the ignition is only turned to the " ON " position, with any other XF ?
If Yes and only on your XF this occur . . . test i would perform if this problem would be on my XF and here is why: If the depressed brake pedal goes down as soon the ignition is turned only to the " ON " position, this would mean that some brake fluid is going somewhere as soon the ignition is turned to " ON " since the engine is not running and their is NO Vacuum at all comming in the brake booster at this point.
Then, this mean that the brake fluid have to go somewhere by some sort of electrical mean only. This would also mean that " IF " the brake pedal is depressed to a fix point, and then, the key is turn " ON " , pressure would drop down in the brake system .
Having the car on four jack stand, place proper lenght of wood between seat rail and brake pedal to the point you can feel a slight presure on all 4 calipers by turning each wheel by hand, then turn ignition to " ON " and compare the force needed once again, to turn each wheels to see if pressure in the brake system as really fallen.
Daniel