Also the c4s has the power brake system and this utilises brake fluid built up under pressure to assist the drivers foot effort instead of a vacuum servo as in the 2wd models, the accuumlator gas filled sphere can loose its abilitity to retain the pressure so the fluid can return back into the reservior (this is not a problem unless the level is too high to start with ) ,If you repeatedly pump the brake pedal without the ignition on you will exhaust the reserve of pressure normally retained within the sphere and the fluid level will rise again, the reason the lights take 30/40 seconds to go out is the time taken to recharge the pressure which bleeds off sometimes.Pressure switch also fails sometimes which can either play up the warning lights of leak fluid into your boot floor!. And as has been said on here previously the fluid level is correct for all situations when: A: the pressure accumulator is charged up (when the pumps buzzing noise stops in the front compartment,with the ignition on and not pressing the brake pedal)) and the discs /pads are new all round and it is on the maximum mark! Dont be tempted to fill to the maximum when the checking condition has not been met and when your pads are half worn all round or it will go everywhere when you overhaul the brakes and push the pistons back (if its too high allready their will be no room for expansion)
The system has been calculated to take account of all factors so if the level is correct with new brakes and charged accumulator then it will not overflow even if you completly exhaust the pressure accumulator.When changing brake fluid account must be taken of the wear present on the discs and pads and the level set accordingly.
