1982 Toyota Pickup Repair Question
Mileage: 160,000 miles.
Toyota Pickup Brakes Problem
Answer
if you crack the line at rear of master where does that line go? does it go to rear of truck or front. If it is a drum type master there is a blocker in there to keep pressure on the drum style brakes. Drum styl ebrakes need this to operate to have a little pressure going to it, disc do not that may be the reason for locking up. if it's a proportioning valve you can always get a self adjustable one as longas it has the correct fittings for it like so many custom cars have.. Not being able to see the truck this is about all the info i can give. there may be a metering valve for the front disc on the crossmember/axle someplace or it's tied in with the pro valve. you don't have any compression fitting s along your brake line somewhere as this wold cause what you are having. if you do remove them an dreplace the whole line or install a fitting on the line with a connector instead of a compression fitting. One other thing recheck your parking brake to make sure it is not keeping your regular brakes applied all thetime. Do the calipers have new kits on them and slide well inside there mounts?
Check the brake booster push rod to master cylinder measurements. When problem occurs, loosen the master cylinder bolts to test if pressure releases.
oneother thing, i'm sending a picture of a load sensing proportioning valve which your truck has, if you have disassemled this, it was NOT meant to be and controlspressures sent to fornt and back wheels. It is connected by back axle. If you have the pressures are screwed upand will need to be replaced as it can be adjusted but you need several gauges to get it. Best thing if this is what is wrong besides what KH suggested because i forgot about that my self, is try http://www.junkyardog.com and type in info. if they have it they can send it to you.
sent the wrong pic lol sorry here is correct one.