You don't say what brand and grade brake fluid you use.
Probably not your problem but this can and does happen sometimes with the 164, and the problem seems to be brake fluid boiling because the tightly packed 164 engine compartment is hotter than other Alfas. After a couple of times of this happening and then changing master cylinders with little effect, changing to ATE Blu (now 200), a higher temperature fluid from the standard called for, eliminated the problem and hasn't returned since.
89 Milano (wife's daily driver since 1989, Shankle Sport)
91 164S (my daily driver since 1994)
94 164LS (~Q) (trip Alfa since 2000)
72 Morgan 27 (water time since 1976)
previously owned since 1964:
62 Morris MiniMinor 850, 67 Austin 1275 Cooper S (Downton 3/4 race), 64 Giulia Sprint GT (1st red one made), 72 Fiat 128 Sedan, 75 Alfetta Sedan, 78 Alfetta Sedan, 78 GTV, 81 GTV6, 86 GTV6
Last edited by Del; 01-14-2017 at 06:41 PM.