Lost the brakes on my 4kq

["Timothy Penasack" <tpenasack@att.net>]

Two weeks ago the brake pedal on my 86 4kq went to the floor while doing 65+
on Rt 128 at 3:30 PM.  I managed to pull over and I dumped a quart of fluid
in the empty reservoir. I nursed it home by downshifting and using the
handbrake. A friend who's a mechanic said he thought it may be the
proportioning valve.  Any other ideas? (Its been in the garage since then
and I'll finally get a chance to look at this coming weekend).  Anybody know
the cost of a proportioning valve? Is difficult to R&R?

TIA

Tim
94 100S non-q - the wife's
92 Rodeo - the dog's
86 4kq - mine (no binders)