Could a leaking master cylinder be causing transmission overfill and brake failure on a Komatsu WA320-1?

[George]

When I got the machine, transmission oil was leaking out of the vent, and I found it about 5 gallons overfull. The previous owner mentioned the brakes needed to be pumped to work, and now I'm seeing the same thing- it takes around 10-15 pumps, and the brake fluid reservoir ends up empty. Here's the strange part: I can't find any external leaks anywhere. From what I've been reading, it sounds like it could be a leaking brake master cylinder dumping fluid into the transmission over time. Does that sound like a likely cause on these machines?

If that's the case:

• Is rebuilding the master cylinder usually enough?
• Or should I be checking other components (like seals, brake valves, or lines into the trans)?
• Anything specific to watch out for on the WA320-1?

I'm planning to use this for a home project on a hill, so I definitely need the brakes 100% reliable before putting it to work. Appreciate any insight.

 

[Mr. McTuggart]

Most likely culprit is the brake master cylinder (or internal seals) leaking internally and slowly dumping fluid into the trans over time.