I am loosing brake fluid no obvious leaks, but fluid does leak from somewhere, new master cylinder new servo after driving the reservoir still full,car then left overnight reservoir 1/2 empty in the morning. Vacuum disconnected and reservoir 1/5 empty what is causing this.
Hello, I hope the following assists you.
I there are no visible leaks at any wheels, pipes and the master cylinder has been replaced then this suggests the fluid is going into the servo. Having said this a new master cylinder shouldn't leak which is the only way for the fluid to get into the servo. Try disconnecting the servo vacuum pipe and use a piece of wire or similar to dip into the servo to see if there is fluid in there.
Also make sure the rear wheel cylinders aren't leaking inside the drums.
If this is repeatedly happening when you top the fluid up then there must be a leak somewhere on the system.
Start with checking these points. let me know if you have more questions and I'll reply as soon as I'm able to.