Brake fluid seep from master cylinder

[Frankb]

68 Charger with late model master cylinder. Brake fluid seeping from filler cap.
At first only aft cap seep so I swapped the caps. Now seep from front and rear.
I removed some fluid from front and back reservoir. Cap seals are good but still leaks from both.
Also brakes don't feel normal - they feel soft but car stops fine. Bleeding does not help.
Lastly I can hear what sounds like a vacuum leak from behind the dash. I thought it was coming from headlight switch. I sealed a small crack on this switch in the past so I installed a new aftermarket switch. Still hear the leak with new switch. I'm thinking maybe bad vacuum power assy??

 

[dadsbee]

Aftermarket crap. I remember Joel @hunt2elk having an issue and finding better caps.

 

[hunt2elk]

M/C pressure bleeding adapter cap
Here is a post showing the replacement part #'s.

 

[tonysrt]

I had that problem also, the cap leaking, I replaced the cap seal and solved the problem. I bought Dorman # 42081 seal.