Hi all, My brake servo wasn't holding a vacuum, it works and passed the MOT but if you sit with your foot on the brake and switch the engine off, you can feel the pedal start to push back. I checked the non return valve with a Miti Vac and by blowing through it and it definitely works. So I thought it must have a hole in the diaphragm and duly purchased a servo. The problem is this one is exactly the same so I no longer think its a diaphragm issue. I am no expert on Servos, but it looks to me that the vacuum side is sealed by the master Cylinder, but when I removed the master the only thing that looks like it might be a seal is a black ring on the cylinder where it sits inside the recess. and unless there's a bit missing it doesn't look like it'll seal anything. Has a PO fitted the master and missed out a vital seal?