Thanks again to all that's helped with this. Yes the brakes bled to a good pressure. I've got a Haynes manual so will look to try and find the servo air filter and replace/clean as necessary before I fit my 4th master cylinder. Thanks very much again everyone. Mark
When you say it's ruining the seals what exactly is happening? Are you saying the fluid is leaking back past the seals?
Are you having to apply excesive pressure on the pedal? As said the hissing is normal. To check if the servo is working correctly, with the engine OFF, press the brake pedal several times till it goes hard then, kepping the pressure on the pedal, start the engine. The pedal should then go down slightly as the servo "sucks". If not check as previously mentioned plus any servo pipes for leaks.
Ex 1.4 Berlingo Multispace
Hi mate. When I say it's ruining the seals I mean I'm losing my brakes altogether. The pedal just goes straight to the floor and I have no brakes at all! I summised it must be the seals but there's no external evidence of fluid loss. Hope this makes it clearer. Thanks. Mark