My vote is the float switch in the master cylinder.

I always wondered why the diaphragm in a master cylinder would expand like that. I thought it was just getting old and would fall because of gravity, but the reasons above make sense to me.

I'd buy a new cap and bleed/flush the brake lines. Good insurance.

John B.

'87 Raider 2.6 Turbo Auto, Under Construction
'95 Montero SR, 35x12.5/15 BFG M/T KM-2's, Rock sliders, Qtr panel chop, gas tank lift, 2" BL, Aisins, 5.29s
'95 Pajero Mini
'98 Montero Winter Ed.
'04 Cadillac XLR
'03 Kawasaki ZRX1200R
'60 Ford Falcon 4Dr