Low pressure brakes

[allanv6gt]

Had an interesting 'symptom' starting Tues night and all Wed, where the brake pedal was lacking/very low pressure until about halfway down pedal travel. Pumping the brakes gave the impression of no master cylinder activity until mid-point in travel with a knocking sound (like air gap closing on pedal connecting rod - bonk!) and squidgy sloshing sounds (not to be confused with normal vacuum suction).
So, being <9months, 17K kms old, and under warranty, I took it back to Ford.
Vehicle failed to 'fail' today when they looked at it. Pedal was firm today when sitting at idle, unlike yesterday. No other work was done or remedial action taken.

My old skool way of thinking suggests a sticking master cylinder piston, or failing seal on half the circuit.
But these cars have so many sensors, split (anti-fail) brake system, ABS EBD etc etc that it is all too complex for me to diagnose/understand....except the pedal suddenly when funny with a 'ping' sound when pressed gently on Tues night.

I have a copy of the job report for future reference.

Anyone else had this problem ?

[allanv6gt]

MB XR5T
-Build late 2009
-Compliance Jan 2010
-Sold July 2010

[yelpir]

Originally Posted by allanv6gt

So, being <9months, 17K kms old, and under warranty, I took it back to Ford.
Vehicle failed to 'fail' today when they looked at it. Pedal was firm today when sitting at idle, unlike yesterday. No other work was done or remedial action taken.

Any chance of hooking up your car to Ford's computer and checking for any error codes?

[allanv6gt]

Dealer found 'no fault' - I would hope connecting to computer to check for error codes has already been done at the dealers 2 days ago. Service foreman at dealer drove vehicle and 'checked pedal' - no mention of computer error code check however.
But unless this happens again....what can you do?
I remain skeptical and very wary.

[apstar]

If I was in your position I would replace the brake fluid

apstar