1970 chevy truck brakes

[oilzumman74]

i hope someone can help me with this i have replaced my master cylinder put a new brake booster new wheel cylenders new brake shoose but i stil have know brakes i have bleed the system i evan blew out the brake lines out thay are clear when i put everything back togather stil no brakes it gose all the way to the floor. so dose anyone have a idea what is going on

[454stepside]

did you pump them up and bleed them ?

[lolife99]

Did you bench bleed the master cylinder?

[sjarrett71]

Did you bench bleed the master cylinder before you installed it?

[wilbilt]

Are the shoes adjusted so there is a very slight drag on the drum?

[70cst]

All good ideas...and the answer is?

[oilzumman74]

i pump on the barkes but stil not a thang. i just put the master cylender on the truck and bled it on the truck . the shose are barley tuching the drum it is a drum to drum system

[oilzumman74]

how can i tell if the porping valve is working i thank i spelled it right

[oilzumman74]

i pumped up the brakes but it would stil go all the way to the flood

[wilbilt]

When you bleed the brakes, have someone just step on the pedal and hold it about halfway down. Don't pump it like a madman or you will cause the fluid to foam up.

When the pedal is held down, crack one of the lines loose at the master until the air/fluid stops squirting out, then tighten the line and have them slowly let up on the pedal. Repeat this several times on both MC lines until you get clear fluid out, then starting bleeding the wheel cylinders the same way.

Also, make sure there is a little bit of play in the linkage between the brake pedal and the master. If the pushrod is too tight, it won't let the MC piston return all the way, which will prevent the MC from refilling with fluid from the reservoir.

[oilzumman74]

i put on a brake booster dose the truck have to be running?

[wilbilt]

Originally Posted by oilzumman74

i put on a brake booster dose the truck have to be running?

No, it does not have to be running.

When you bleed them, are you getting fluid out of all 4 bleeders?

[bmfm64]

Take the master back off and bench bleed it to start with, then you'll probably have to reset the proportioning valve, then you can start the bleeding process. It will probably take a while and several trips around the truck if you actually blew all the fluid out of the system to get all the air out as that's all you have right now.

[vectorit]

A little video on bench bleeding a master cylinder.

Dual Brake Master Cylinder - How to Bench Bleed...

[oilzumman74]

the proportioning valve dont have a reset

[wilbilt]

Originally Posted by oilzumman74

the proportioning valve dont have a reset

Sometimes they get stuck if the plunger has been forced all the way in one direction. Are you getting fluid out of all 4 wheel cylinders? If so, it is not stuck.

[Stricklinator]

I don't think 67-70 has a proportioning valve, just a distribution block with the warning light switch. You probably just need to bleed the master cylinder completely before re-bleeding each wheel cylinder.
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[lolife99]

Originally Posted by Stricklinator

I don't think 67-70 has a proportioning valve, just a distribution block with the warning light switch. You probably just need to bleed the master cylinder completely before re-bleeding each wheel cylinder.
Posted via Mobile Device

X2
It's just a distribution block on 4 wheel drum brake trucks.

[cdowns]

a drum brake system has no proportioning valve// i has only a distribution block no pin to reset

[wilbilt]

The early combination valves did contain a residual pressure check valve (to help keep the wheel cylinder cups expanded), but did not necessarily have metering or proportioning functions. If it is a dual-reservoir master cylinder, which it should be for '67 and has a brake warning light switch, it does contain a plunger to isolate either side of the system in case of pressure loss. Otherwise, there would be no point in having a split system.

These can and will get stuck in one direction or the other and some of them (early Econoline vans for example) can be a real bear to re-center due to not having a "reset button".

[oilzumman74]

i have brakes now the ms was bad and i just put it on there not long ago i went back to the auto parts store and let one of the guys look at it and he sed the plunger was mested up so he gave me another one and he put it on the bench and bled it for me so that was all it was but i have brakes now this truck has ben a pain just glad it is over now. now to fix the floorbord and some outher stuff thanks for the help

[oilzumman74]

if i miss spelled something let me know

[bmfm64]

Originally Posted by oilzumman74

if i miss spelled something let me know

You misspelled something. Glad you have brakes though! And I'm not sure how exactly you got the parts guy to bleed your master cylinder but that's awesome!

[litew8]

Originally Posted by oilzumman74

the ms was bad

That's what I was going to say the problem was!