Rear Brakes Won't Bleed?

[Kisner]

With the help of my mechanic friend, replaced my 68 coupe's rear wheel cylinders and rear parking brake cables this past weekend (both cylinders were leaking). After we put everything back together (along with all new springs), we couldn't get the brakes to bleed. Guess we tried for an hour and a half. Fluid initially dropped in master cylinder but then stabilized and didn't drop any more. Not a drop of fluid would bleed. Think we tried everything. The front brakes bleed fine. Could my lines be clogged? If so, what do I need to do - remove the lines from the master cylinder all the way back and blow them out with an air compressor? Any help would be appreciated.

[Gearhead999]

The proportioning valve has shifted over and shut off the rear brakes.

Fine the valve. Left apron, under the mastercyl. Pull the electric switch out of the center. [It's the part with a wire] Put a sharp, pointed, instrument down there and move the valve to the center. Hold the valve there and bleed the brakes.

KD and other companies use to make a tool that you could screw in there to hold the valve. I don't know if you can find it anymore. Anyway, if you can't.....fabricate something to hold the valve and bleed the brakes.

Just a typical old car.

[Kisner]

I was wondering if the proportioning valve would have anything to do with it since I knew it was off center (warning light has been on for the 2 1/2 years I've had the car). Never even realized the back brakes have never worked. I'll try your suggestion tonight when the wife gets home (so she can hold the valve in place, oldest daughter can pump the brakes, and good old dad in the back operating the bleed screw). Will let you know if that solved my problem. Thanks.

[Kisner]

As my luck would have it, I was unable to move the proportioning valve. After I removed the brake warning switch, the very small hole where the end of the switch goes into just isn't big enough to get any type of leverage with the smallest sharp, pointed object I could find. If I could have possibly got the point into the hollowed out area I might could have manually moved it. However, the valve has moved all the way to the rear, therefore, all the point hits is flat metal. Even tried the shop manual's instructions to loosen the the outlet port to the front brakes to release the pressure, pump the brakes, and supposedly the sole pressure from the rear would move it back. However, it didn't budge that way either. Not sure what to do now except find another proportioning valve (I've been calling it the brake fluid distribution box from the catalogs) but nobody sells one for a 68 with standard drum brakes. Is it possible to remove this thing, take it apart, and some other way get it moved back to the center position?

[Fostang]

The easiest fix would be an adjustable proportioning valve made by willwood and sumiit sells them for somewhere around 50 bucks. Or you can go to a pull it yourself yard and find yourself one from another car. The torino had this same problem this past weekend. Eventually found one at a local wrecking yard and took the inside components and used them to repair the porportioning valve that was on the car. Good Luck

[MDF99]

F.Y.I. The correct term for that part is "distribution block". A proportioning valve is adjustable and used to give more or less braking force to the front or rear brakes. The distribution block is a non-adjustable piece.

[Kisner]

My lucky day. Metro Mustang in Georgia has original used ones for the 68 with standard drum brakes for $45 (can't find anyone who makes a reproduction for the 68). Expensive, but want to keep it as much original as I can. Only drawback is they can't tell me if it works or if the valve is centered. However, if it doesn't work, I can send it back and they'll keep sending me one until one does. Now my new problem - the rear brake line nut on the dad gom thing is froze shut. 3 days of applying WD-40, tapping it, and using the appropriate brake line wrench hasn't produced a nudge. Only thing I know to do next (before I use the hax saw and then have to buy a new rear brake line) is to try my vice grips. Any suggestions?

[MDF99]

you might try heating it with a propane torch a few times first, good luck

[Mach1 Cobra Jet]

Try using JB-80 instead of WD-40 and make sure you are using a flaring wrench and not just a regular style wrench. If not you may round off your fitting. Be careful if you use a torch and stay away from fuel lines. Hope this helps.

[Kisner]

Update - my luck finally changed and after 3 days of soaking in "liquid wrench", the brake line nut broke free and I removed distribution block. Thought I'd experiment and remove end nut and see if I could grab hold of end of piston and pull the proportioning valve back to the center position. After 2 hours and 3 pairs of tweesers (only thing that would fit in the end - squeezed them with my needle nose plyers), was able to forcefully pull the valve back to perfect center position. Cleaned it up with fine steel wool (was painted black over the years when they painted the engine compartment) and now it's brialliant , shiny brass again. Cleaned it inside and out - B=brand new looking just like it was in 68. Now to see if I can get a refund on the one I already ordered.

[shovelnose]

Glad you found your problem!

I had the same thing happen but it was rust/dirt? plugging the line. I opened the bleeders and pounded the brake pedal and then got some fluid.