No brake fluid coming from back reservoir on new master cylinder

[gxc]

We ended up having the original master cylinder on the truck and we bled the breaks and everything worked fine except the master cylinder was leaking so we ended up replacing it. Now we've got three brand new master cylinders and I bench bled the third one we got and I still can't get any beak fluid to even come out of the back reservoir. It's on a 1972 chevy c10 by the way.

Can anybody help me out with this? Because we can't figure out why in the hell we can't get any fluid to come out.

[T3AMCH3VY]

If you have the master cylinder in a vice, the reservoir full, pushing the piston all the way in, and you are not getting any fluid out I would have to say it was a defective master cylinder.

[gxc]

Well we bought two already and didn't bench bleed the master cylinders so we returned it and then bought another one from a new place and I actually bench bled this one and we're still not getting any brake fluid out of the back reservoir.

[litew8]

Is this how you bled them? If yes and all looked good, could be
something wrong down the line. What do you mean when you say
there is no fluid out of the back reservoir? After it is connected to
the truck and lines I assume - since you are seeing the movement
of fluid when bleeding, correct?

http://www.youtube.com/watch?v=UHDn46lbwtM

[gxc]

Okay I never got that bleeder kit when I bought the master cylinder, I got two blue screws to plug the holes where the lines get attached and pushed the thing in with a screwdriver. Maybe I need to go back to autozone and ask them about that bleeder kit. And no there's no movement after it's been hooked up to the truck and the lines have been connected. I don't believe anything is wrong with the brake lines. They were both working just fine with the original master cylinder.

[ho70]

I just did my MC and no bleed kit and just theose block off screws. Bled the MC and no fluid out the back lines, screws were plugged but gonna have to check the wheel cylinders

[litew8]

Ok, sounds like they weren't being bled correctly, after rereading the comments. Yeah, you need to bleed it like the video shows and be sure not to allow any air into the 'system' when connecting to the truck, from the bench. Pinch the bleeder lines good when going from the bench to the truck to ensure no air gets into the MC. Alternatively, you can bleed it while connected to truck. Brake pedal = screwdriver. 2 person job better.

[gxc]

I have to go back to autozone and ask them about the kit that was suppose to come with it. We were getting fluid out of the original master cylinder but we had to replace it so I guess we just didn't bench bleed it correctly. And, we tried bleeding it when we attached it to the truck but still weren't getting any fluid from the back reservoir to the brake lines however, we keep getting fluid from the front one.

[Lee H]

Bench bleeding is a must. Most rebuilt master cylinders no longer come with a free bench bleeding kit, they are sold separately. Did you make sure the proportioning valve was in the proper position for bleeding the system?

[gxc]

Originally Posted by ho70

I just did my MC and no bleed kit and just theose block off screws. Bled the MC and no fluid out the back lines, screws were plugged but gonna have to check the wheel cylinders

Seems like we have the same problem here.

[gxc]

Originally Posted by Lee H

Bench bleeding is a must. Most rebuilt master cylinders no longer come with a free bench bleeding kit, they are sold separately. Did you make sure the proportioning valve was in the proper position for bleeding the system?

Yeah the proportioning valve is in the correct position. I'll have to stop by autozone and buy a bench bleeding kit then.

[geezer#99]

Did you depress the button on the prop valve to get it to bleed?

[sduckworth13]

Maybe you need to adjust the pedal rod that goes into the brake master cylinder. I was having the same issue as you and once I adjusted the rod it was good to go. Give it a try and let us know how it turns out.

[gxc]

No because we weren't getting any fluid to come from the master cylinder. We're gonna buy a bench bleeding kit from autozone this weekend and try and bench bleed it and get it figured out.

[gxc]

Originally Posted by sduckworth13

Maybe you need to adjust the pedal rod that goes into the brake master cylinder. I was having the same issue as you and once I adjusted the rod it was good to go. Give it a try and let us know how it turns out.

We're gonna give that a shot here this weekend and I'll update you guys about it.

[sduckworth13]

Originally Posted by gxc

We're gonna give that a shot here this weekend and I'll update you guys about it.

It is nerve racking to know you've replace two master cylinders and still no fluid and then you start looking for kinks in the lines, leaky wheel cylinders, and loose brake lines etc. I was doing all of that. When you adjust the rod make sure you don't adjust it to far it won't need much adjustment. Good luck

[T3AMCH3VY]

If your still having problems gravity bleed the brakes. Fill the reservoir and crack all four bleeders open. Go inside a grab a beer, by this time you should have a good stead drip from the front bleeder screws. Next you drink the beer and by the time your beer is empty you should have a steady drip from the rear bleeder screws. Some manual bleeding may be necessary to get last bit of air out.


Its also a good idea to pop the top off the reservoir a couple times to make sure you are not building up a vacuum that would stop the fluid from draining.

[ho70]

didn't bleed with proportioning valve attached. Is it the 'knob' at the end and what position should it be in?

[hilinerider]

going thru the same battle on my 70 k20, started with just one front wheel working, all new brakes,rebuilt wheel cylinders, new master cylinder and a gallon of dot3 thru the system and still have just the right front working but now only after three hits to the pedal, very frustrating and scary when she's your daily driver

[hotrodder]

iif the problem is no fluid at the rear bleeders it might be the rear hose is deterated on the inside and no fluid can pass through. I had that problem on my 63, changed the rear hose and success!

[jocko]

You can bench bleed with only the blue screws, that will work. I believe Lee and geezer hit the nail on the head. The combination valve being "in the correct position" means that the internal shuttle valve has been centered. This is important - failure to center it will mean you have either no front or no rear brakes, depending on which direction it is off center. Is your dash brake light on? Was it on before? If yes (ie, if it's working) this is the reason why. Simple way to center the valve is a few sharp, hard panic stops on the brake pedal (while sitting still, in Park). This is a finicky system, but also a good safety feature.

[Lee H]

I'd like to add a note about bench bleeding. Syringe bleeding, I've done two now and it's way easier than the conventional pumping with tubes in a vise. I did both with the master installed and the lines connected. I will never use the old way again. Just Google, lots of info and YouTube videos.