I don't have a CPP proportioning valve in my 55 but out of curiosity I started searching the Internet.
It's called a weep hole and the leak has been noted to occur when the proportioning valve fails.
Comments I have read mentions failure due to new parts residue not removed (extra cleaning needed) before the valve is assembled.
Comments say it leads to wear or leaks around the seals or deformed seals.
Of course it is assembled in Asia and CPP is aware of the problems but it has been going on for many years...FROM WHAT I HAVE READ.
Do your own research or call CPP and ask.
Symptoms are leaking and/or soft brake pedal due to empty reservoir.
CPP has been a good company I really hope they can resolve the issues for the long term.
In the meantime, check your reservoir level before you head out of town. Carry a can of fluid with you.
Don't be stranded in "podunk' trying to get your brakes fixed.
