Diagnosing master cylinder failure 92 disco tdi

[brendan leier]

My truck as been displaying some mushy braking, reservoir still full. Alas, my memory has failed me as I have replaced my master cylinder back in the day l, but can't recall the presentation. To complicate the matter, my disco still uses the elaborate RRC brake system with dual reservoir and multiple nipples per caliper. What is the quickest way to diagnose master cylinder failure? 

[binch]

Now I'm not saying I have a clue what I'm talking about but....

I'm not sure about the double brake cylinder stuff but I've found from personal experience that the mushy brake is one of two items.   If the brake pedal is soft to start with then you might have air in the lines.   But if you are stopped at a light holding the brake pedal down, and it slowly wants to go to the floor still then you have a leak.  If you don't see brake fluid loss from the reservoir the seal(s) in the master are gone and allowing the fluid to pass the piston within the master.

[brendan leier]

Many thanks Bill! I recall having to actually Jerry rig a reverse bleed because those calipers are quite complex, three nipples per.