FJ40 Brake issue. I am losing my ever loving mind! (1 Viewer)

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took the proportioning valve off a few years ago because I was having a lot of trouble getting the fittings to match up. The brakes ran just fine without it for a few years. I asked the guy doing my brakes if we should put it back on and he said it would be fine without it, just be ready for your back end to shift.

This is the valve I took off. But again the brakes worked great without it. I am down for reinstalling it if you tell me it might help.View attachment 2828121
That is NOT a 1978 Toyota proportioning valve. Looks GM to me. It may work as well as an original but I wouldn't know.

On a 78 disc/drum set-up only the rear line passes through the prop valve. This is to prevent rear wheel lock-up. There's no other way of doing it as, with a tandem MC, the rear piston is the same (or could be larger) diameter as the front and receives the same stroke - i.e. - volume. The valve meters it down.
 
78 MCs do have front and rear residual valves as seen here: MC Breakdown

78s do not have rear e-brakes. They have the drum set-up at the t-case output.

tempimagemfcer8-png.2828257


That is a '78 master cylinder. The previous one is a generic aftermarket set-up sold by a lot of places. What's left of Man-a-fre is one.

Where you're pulling vacuum from to the BB is where your PCV valve should be hooked up. The OEM spot to hook the booster is on the top of the intake between the 5th and 6th intake valves. Probably not an issue other than the crankcase gasses would be drawn into all the cylinders evenly if hooked up correctly. Just pointing out/adding a few things here for future reference.
 
So we finally fixed the problem!!! It was a leaking gasket in the carburetor... That was my last ditch effort to think outside the box because I tried everything else. Did a rebuild on the carb and found the gaskets were almost completely gone. Fixed that and I have 80% better brakes. So I think there is still a small leak somewhere but I can definitely stop the truck! Thank you guys for helping me I really learned a few new things about my FJ.
 

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