4.2 Brake Sesrvo Wheeze

[Dr-G]

All,

'64 S1 4.2 Coupe

Does anyone else have a loud "wheeze" noise from the remote servo when pressing the brake pedal? Also comes with a slight temporary vibration which can be felt through the toeboard.

Mine was a new unit many years ago, and has done less than 1000 miles in total - it's always done it. A strip down and inspection showed nothing obviously untoward.

The operation of the brakes is unaffected, but it sounds terrible. It's coming from the diaphragm, and isn't present once the vacuum reservoir has been exhausted. There is no obvious vacuum leak.

It's something to do with the rubber diaphragm and/or how it interacts with the piston and casing.

Thanks.

[caveman]

Mines silent.

[christopher storey]

This is absolutely characteristic of the remote servo on 4.2 and later cars. If you repeatedly press the pedal with the engine switched off you will hear it gradually diminish in volume and intensity over about 8 presses until you hear nothing . The noise, and the knock which can be felt through the toeboard, is caused by the movement forwards of the diaphragm and its support when vacuum is admitted to the front chamber of the servo . Absolutely nothing to worry about as long as the brakes are otherwise working normally

[Dr-G]

Thanks both.