406oc.co.uk

Hi. Have an 2004 406 V6 saloon. My problem is the brake(s) pedal. When driving at normal speeds, calm and relaxed the brakes work fine but there is an high pitched sound from the the pedal area and in the engine compartment both while driving and standing still on idle( disapeers when tapping the pedal). Also there's air beeing sucked in from the cabin where the brake rod goes into the bulkhead. And when I go full throttle whilst for an example passing the car in front and have to brake fast the pedal is hard as stone with almost no braking power. But when going into a roundabout at lows revs accelerating and need the brakes it almost goes to the floor and it takes a little time for brakes to take?
Atfer reading a hole lot on the subject I have 't found exactly the same issue but similar. I suspect the brakeservo. Any ideas anybody?

Sorry to hear your troubles mate, dodgy and especially intermittent brakes can be a very scary thing!

Servo is potentially the issue but I'd look at the simple stuff first, check the pipes off the vac pump first and any T's that come off it. Not familiar with the petrol setup but you potentially only have the EGR feed to worry about.
Also the pump itself may be getting tired so check it's giving a good level of vac pressure but I've no idea what it should be putting out.

The fact that the pedal is sinking sometimes and hardly moving others makes me lean towards pipework rather than servo as I'd imagine a leaky seal there would give a consistent feel on the pedal one way or the other.

This might help but there does appear to be 2 brake options for the V6, Teves or Bosch but both a similar setup

I think its the servo too, although as Gumby says, blank off each vacuum feed one at a time with a golf tee or similar and this may pinpoint the leak.

Does your car have a vacuum reservoir? Its a long oval shape plastic flimsy container just below the servo - these can leak too - bypassing it will eliminate it from the list of suspects....

When my servo failed I had a rock hard pedal with no brakes, then 2 seconds later the brakes would work and almost throw me through the windscreen because you are standing on the pedal by then... There was also a loud hiss when I released the pedal which could be heard with the bonnet up but the engine off.

The servo may be part of the problem, but does not explain the pedal going down to the floor and braking coming in after a pause. I have only come across this problem twice, on other cars, and it was the master cylinder that was at fault.

look at the servo if it has traces of lekedge on the frount then you have a master cylinder fault that has taken the servo with it