I have been suffering with a problem with my brakes for quite a while now and have replace braking components without any joy.

The problem with the brakes is that when I first apply the brakes for the first few times after the car has been stood still for a while the braking performance is very poor.. What I mean by this is that when you press the brake fully it feels as though you are braking without the aid of the brake servo and therefore takes a while to stop. Once the brakes have been applied a few times they work fine.

What I have done so far to try and fix the issue without any luck is:
- Changed the brake servo and master cylinder
- Replaced brake disc's and brake pads all round
- Flushed brake fluid system with new fluid.

Just for your information in case anyone asks I have checked to see if the servo is working correctly by applying pressure to the brake pedal when first starting the car and seeing if the pedal drops, which it does.

Any help would be much appreciated.

My car S Type 2.5ltr 2003

 

At a guess it's not vacuum-related but I hate to guess so how about looking at OBD live data (specifically fuel trims). A tool such as elm327 is about a tenner. See if they vary and how:
as it warms up
before, during and after the problem manifests each time

A separate idea: if you let the car stand (so it would show the fault) but instead of using it to check the fault shows start the engine and let it warm up for an extended time (going to be very boring). Then try it. I'm thinking that if it's just heat-related (a seal or some such) then it will not show the problem.

I'm trying to think of a whether the ABS/DSC module could be involved (its hydraulics I suppose) and how to tell! Some have been found to have poor solder (DIY-fixable) but I don't see how it would show up this way.

 

^^^brilliant^^^

 

Unhook and plug the vacuum line going to the brake booster.

Go for a drive. Let us know how the pedal feels and how the car stops.
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Just for fun- how healthy is the parking brake?

Try this test. With the car rolling along at idle at approx 10MPH/16KPH and a clear road in front and behind you, slip the transmission into neutral. Without touching the foot brake, start applying the park brake by lifting the park brake lever repeatedly.

As the car comes to a final (and abrupt) stop, does one side of the car seems to dip or raise more than the other?

Put the transmission back into drive, again without touching the foot brake.

Does the car creep forward, or one side raise/lower more than the other?

Lightly touch the gas pedal to disengage the p/brake and release.

Again, any difference side to side?

I've discovered that the p/brake lever on the rear caliper must travel though it's full arc each and every time it's applied/disengaged, If not, the pads will not self-adjust for wear and gradually that wheel will lose braking efficiency.

The foot brake pedal will seem lower than usual and require higher than normal foot pressure in order to stop the car. I've got an actuator cable on mine that annoyingly stick now and then- these are the effects.