No power in brakes and sinking to the floor??

Hi,

So this all started with my rear passenger caliper bleed valve leaking fluid and it was because the valve wouldn't close back up due to ruined threads on the caliper (Bought this car from somebody 2 weeks ago), it lasted the 2 weeks but then fluid was all over the place so I had no choice but too replace my brake caliper.

I have now replaced the caliper myself and changed the pads and disc as well as I had it opened already.. I also bled the brakes from the brake valve and a lot of air did come out... It is also worth mentioning that the master cylinder was bone dry the next day when I came to replacing the caliper... So any way.. caliper installed and I bled the bleed valve too until only fluid was coming through and the pedal was nice and hard.. Tried a little test drive and I have literally a very small amount of brake power .. I am also experiencing the brake pedal just sinking to the bottom I thought, maybe I should bleed all 4 valves?

So, I did and this made no difference at all.. When engine is turned off.. the brake pedal will get nice and hard but when engine is turned on .. the brake pedal sinks to about 3/4 of the ground... Not much brake power as I put my foot down on the brake and the first quarter it brakes sharp but ones the pedal starts sinking.. I get no brakes ...

What is the solution to this!? It is driving me crazy and I have bled and bled and bled all 4 valves 10 times with no difference at all .. Is my master cylinder gone because of it running dry?? How much would I get charged for replacing the master cylinder here in the UK ?


Thanks.

Either master went bad from sitting (depends on how long it sat) or there is still air in the system. Try a power bleeder if you can find one

eurocars said:

Either master went bad from sitting (depends on how long it sat) or there is still air in the system. Try a power bleeder if you can find one

Click to expand...

Okay so I took it to the garage and he told me "You cant just bleed a Golf MK5 manually.. You do it by computer" so he did it using a VAG COM and followed the instructions etc on the computer and now it feels better but the brakes still loose power at the end of the pedal press.. He said, it is fine, it should be like this but when I bought the car 2 weeks ago and before the brake change.. The brakes would work with just a quarter of a pedal press Would like it like that because at least then the brakes seem like they are working -_- Oh well.. If the garage is telling me it is working like it should then I guess I will have to believe them right

Sounds like there's still air in the system. He bled the ABS pump. There's usually no need to do that but since your master cylinder and most likely ABS pump ran dry, it was necessary.

Like someone else suggested, try a motiv power bleeder. Look into a Phoenix System reverse bleeder as well.