front brake / master cyl issue

[chillinfellow]

Have a 78 kz 400, front brakes just starts to grab on disc when pulling lever in then loses pressure, there is no leakage at master cyl or caliper, pulled master cyl cap fluid was lil low topped off, no change, then tried bleeding couple times, also had pulled caliper off and raised above the master cyl as a last resort to draw out any air possibly trapped, still no change, Noticed that fluid was greyish in color, so I guess I am seeking possible confirmation or alternate solutions if my assessment is incorrect, having some mechanical intuition I am suspecting what is referred to as the "piston-comp-brake" according to actual part description, which is labeled as #12 on the attached diagram, I am assuming that the rubber seals that are on it are shot, which would probably explain why the fluid is grey because of the deteriorated rubber from the lever piston thus not being able to keep any pressure once back pressure builds from the caliper :-\?? * also attached is a pic of the actual part I suspect, chime in let me know, thanks

 

[crazypj]

If brake fluid is anything other than 'clear'/'golden' it's done.
Needs to be completely drained and flushed.
You would be better off stripping complete system and change brake hose (there will be a date on it, should be less than 4 yrs old (yeah, probably 24 yrs or more old?)
There are two holes at bottom of master cyl, one about 1/8" dia and the other about 0.75mm or less.
The small one is probably blocked.
Repair kit for Master cyl and caliper would be a good idea

 

[chillinfellow]

thanks pj, probably tear into in the next few days