Bad Proportioning Valve?

[georides]

Hello there from New Jersey, USA

We were gifted a 1987 Supra Automatic non-turbo to resurrect, we've done a solid "tune-up", new starter, fluids, etc. problem now is the brakes.

On inspect the front pads were toast, while the rear pads were still thick, we got new rotors and pads in the front, and refinished the rears.

Did a line flush, but rear bleeders keep spitting out bubbles, pedal feels like air in the system until front pads engage (front calipers bled fine).

I would assume this is proportioning valve problem, we're going to disconnect it today and see if we can unscrew the valve on the bottom.

if our inspection cleaning makes no changes What would you think about just bypassing this valve with some new line splices?

[Bill UK]

I must admit I didn’t know there was a proportioning valve, unless you mean the T piece # 9. One problem I did have, and it may be worth checking; is that the small hole at the end of the bleeding plug had become rusted over and blocked preventing any fluid from coming out. Don’t forget to start at the wheels (rear) furthest away from the brake reservoir when bleeding.

[Bill UK]

You learn something new every day on here, Link I can`t remember seeing one on the Supra though.

[Bill UK]

You’re right georides it does have one, too dark in the UK to have a good look. But the manual shows it as part of the master cylinder unit.

[georides]

Guys, thanks for the replys,

I assumed it was called the proportioning valve re this ebay post, mine sort of looks like this:

eBay Motors: 1983-86.5 TOYOTA SUPRA MA67 BRAKE PROPORTIONING VALVE (item 130253416595 end time Mar-06-09 14:08:09 PST)

We removed it today, bought two unions and a short ready-to-bend piece of brake line and actually successfully bypassed the valve, but we do have all the lines, if we decide to put it back.

We started to bleed the rear wheels, it made a big difference, good solid line of fluid, pressure build up when pumping and release on bleeder open (which have been replaced, thanks for the pic)

We attempted bleed of front, got the same squirting froth that we had on the rear wheels, now it makes sense that we had switched the outputs.

I assume now that the problem is the master cylinder, which was my original assumption, though because the "toyota kid" at work said that it was federal mandate since the '70s the cars were diagonally split on brake cylinders, this way if there was a leak at least you'd have front and back, but remembering replacing a line of my uncle's GMC Sierra, he had a "T-Split" as seen in your schematic.

Tomorrow I order a new MC, should have done this first out. pics later

[georides]

OK, Master cylinder did the trick, luckily I hadn't totally destroyed the old lines so we could put back the valve that we removed.

Amazing how firm a new rebuilt one can be, even with a ton of air in the lines, before bleeding, tough and firm compared with the squashbuckler of before.

thanks for the help compadres