1968 c10 brake proportioning valve

[missionstreettattoo]

is it possible that this is the reason i cannot get any pedal to my brakes? i have bled three brake fluid bottles through and it still goes to the floor. i got a master cylinder bleeding kit and di that. still to the floor. the shoes are adjusted out properly. the proportioning valve is the only thing left.

[missionstreettattoo]

why does my truck with drum brakes even have what is called a disc brake proportioning valve? and can i just bypass this?

[lolife99]

Originally Posted by missionstreettattoo

why does my truck with drum brakes even have what is called a disc brake proportioning valve? and can i just bypass this?

They don't.
Drum brake trucks just have a distribution block.

[missionstreettattoo]

this is what is below my master cylinder. I have drum brakes all the way around. i can bypass this right?

[missionstreettattoo]

so is this something i can remove and connect brake lines directly to the master cylinder? any thoughts? this is my last place to look in finding why i cannot get anything but a saft pedal. straight to the floor. no matter what i have done.

[lolife99]

You can remove it,... but you will lose your brake light switch.
You may have a bad M/C.
I would bench bleed it and try again.

[Ridgeclimber]

Is your master cylinder new? It's hard to tell from the picture. If the master cylinder is used, maybe the cup seals in the master cylinder could be leaking by causing the pedal to go down. If the master cylinder is new. Start by bench bleeding it, slowly. Don't pump it hard and fast. If there is air in it you could break up the air and air rate the fluid. Then instal the cylinder and start by bleeding the right rear wheel first. Then left rear, then right front then left front. Again pump the pedal slowly and don't turn the air and fluid into foam. Good luck.
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[Mister-B]

Get a new master cylinder for $17, and bench bleed it. Your current one has probably gone bad
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[cdowns]

i have found buying and reading a factory service manual for a particular vehicle can help you know what you have and how to fix it

[Steve Cole]

I have never seen bleeder screws ON the master cylinder before! WOW! Are they tight when your pumping? You did put the cap back on, right? Sounds dumb but it could happen. Do you EVER get a tight pedal? or is it always soft?

[Ridgeclimber]

Is the pedal just low towards the floor or is it spongy. That is two different problems. If the pedal is low could be brake shoes out of adjustment or be shoes not seated into the drums. If the pedal is hard then creaps to the floor it could be the master cylinder leaking internally. If the pedal is just spongy then it could be air in the system. Just another thing to consider.
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[missionstreettattoo]

if it sits any time at all, the pedal goes straight to the floor, after a few pumps, there is pedal again. the master cylinder was bought new at oreillys a year ago and installed then. only in the last month have i gotten all the lines and things replaced and hooked up.

[missionstreettattoo]

so the bleeder valves on the mc are strange?

[Mister-B]

Originally Posted by missionstreettattoo

if it sits any time at all, the pedal goes straight to the floor, after a few pumps, there is pedal again. the master cylinder was bought new at oreillys a year ago and installed then. only in the last month have i gotten all the lines and things replaced and hooked up.

Have you bench bled the master cylinder yet? If not, you need to stop what you're doing and go do that. What's happened with your brakes since a year ago when you bought the MC? Did you get a leak, have a cylinder go bad, etc? If so, this could have allowed your pedal to travel further then it should. Mix that with all the to the floor pumping you've done, and you probably have a shot MC now. If you want to save some time and aggravation, I'd recommend you buy a new $17 MC, bench bleed it, install it (keep the block below the MC in tact), bleed all the brakes at the cylinders, and then tell is how it went. See, some of us have gone through something similar to this not too long ago, wink wink.
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[missionstreettattoo]

well the truck never ran. it was parked the whole year ive had it,but i guess my next step will be a different master cylinder, just do it and see what happens.

[Mister-B]

Originally Posted by missionstreettattoo

well the truck never ran. it was parked the whole year ive had it,but i guess my next step will be a different master cylinder, just do it and see what happens.

And don't install the new MC without bench bleeding it first, or you'll have issues still
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