Brake fluid being rejected from master cylinder?

[jbassC10]

I'm thinking the master cylinder I was given to buy was the wrong one for the wrong year and I didn't know that yet installed it and it's cause the back pressure or there's something I'm missing?

I've bought a new one which you can see in the photos that looks different where this one is for the correct year 69.

I've bled and bled and BLED the brake lines, checked for air leaks in the line yet I haven't solved the problem?

I've asked a few auto placees (auto zone, auto parts..) and they've all given me different anwsers.
So here I am my Chevy family, lol I'm here to ask what's up?

I was told by one guy I need a "brake valve" or "balancer/valve" to level out the correct brake presure... soooo ??? What's up guys....? What am I missing?

[Ironangel]

Did you "bench bleed" the new MC? Then bleed all four corners starting with the front left, right front, right rear, and then the left rear...Nearest to farthest clockwise.

[jbassC10]

Wow, thanks so much for that info!
I have never been taught to bleed completely from the very beginning. Well now that I have a new master cylinder I know what the first step is! : )

Thanks so much!!! Lets hope that's the only problem because I know that step I didn't do in the beginning.

Later!

[Ironangel]

Good lookin motor and clean motor bay...let us know how the brake issue went... PS. Let see the whole truck!

[jbassC10]

Hey thanks!
Yea, I haven't fixed the problem yet, but here soon I'm gonna put sometime into it!
Sadly right now I'm working 6 days/night shifts for 12 hours. lol So my body is gone by day light! lol But soon will see what happens!

[knomadd]

I've always been taught when you bleed brakes to go farthest to nearest as related to distance from the master cylinder (Passenger Rear, Driver Rear, Passenger Front, Driver Front). It has something to do with getting the most amount of air out of the lines on the farthest run. Since air compresses more than fluid, it's possible that by starting nearest to farthest, you can suck air into the master from a corner that's farther away. This is obviously more likely to happen if you have just installed new brakes and lines.

However, if you have a dual bowl master (separate front and rear chambers), it shouldn't matter if you do front or rear first, but I always start farthest away from the master, and finish with nearest.

That's not to say that it can't be done another way...

[jbassC10]

Originally Posted by knomadd

I've always been taught when you bleed brakes to go farthest to nearest as related to distance from the master cylinder (Passenger Rear, Driver Rear, Passenger Front, Driver Front). It has something to do with getting the most amount of air out of the lines on the farthest run. Since air compresses more than fluid, it's possible that by starting nearest to farthest, you can suck air into the master from a corner that's farther away. This is obviously more likely to happen if you have just installed new brakes and lines.

However, if you have a dual bowl master (separate front and rear chambers), it shouldn't matter if you do front or rear first, but I always start farthest away from the master, and finish with nearest.

That's not to say that it can't be done another way...

Hey! Thanks for the word there! I'll try and do that- Fartherest to Nearest. Good thought really! General terms that seems more sensible. Anyways, wish me luck!!! Thanks again!!

[RichardJ]

I'm thinking the master cylinder I was given to buy was the wrong one for the wrong year and I didn't know that yet installed it and it's cause the back pressure or there's something I'm missing?

I've bought a new one which you can see in the photos that looks different where this one is for the correct year 69.

I've bled and bled and BLED the brake lines, checked for air leaks in the line yet I haven't solved the problem?

WHAT???

"given to buy"?? The one on the truck or the new one?

"was the wrong one"?? The one on the truck or the MC in your hand?

The one on the truck is leaking from under the cap, probably because the rubber reservoir diaphragm is torn. It also appears to be leaking out the back next to the booster. That MC is a wreck so it doesn't matter that you can't bleed the brakes with it.
If all that fluid came from bleeding attempts, then you should be setting the cap on the reservoir, when you are not filling it. They will spit a little.


The new MC in your hand looks like it has a larger front reservoir (?), so if it does, it was intended for a disc brake application. That really won't matter as long as the piston bore diameter is the same in the old and the new.

[jbassC10]

Originally Posted by RichardJ

I'm thinking the master cylinder I was given to buy was the wrong one for the wrong year and I didn't know that yet installed it and it's cause the back pressure or there's something I'm missing?

I've bought a new one which you can see in the photos that looks different where this one is for the correct year 69.

I've bled and bled and BLED the brake lines, checked for air leaks in the line yet I haven't solved the problem?

WHAT???

"given to buy"?? The one on the truck or the new one?

"was the wrong one"?? The one on the truck or the MC in your hand?

The one on the truck is leaking from under the cap, probably because the rubber reservoir diaphragm is torn. It also appears to be leaking out the back next to the booster. That MC is a wreck so it doesn't matter that you can't bleed the brakes with it.
If all that fluid came from bleeding attempts, then you should be setting the cap on the reservoir, when you are not filling it. They will spit a little.


The new MC in your hand looks like it has a larger front reservoir (?), so if it does, it was intended for a disc brake application. That really won't matter as long as the piston bore diameter is the same in the old and the new.

Its the one mounted under the hood there. The new there is specifically for this year, where I know the other is totally different as you can see. But I'll double check the diaphragm and see if it's tore to. Good eye!
So the next step for me is to get some bleeder lines and do that step first and then install it. So I'll do some checks before i start the installment on the old one (tore diaphragm) and make sure to take the right steps! Thanks!!

[Boog]

Also worth mentioning is the fluid level in the master cylinder does not need to be full to the top. Over fill can be pushed out.

[jbassC10]

Originally Posted by Boog

Also worth mentioning is the fluid level in the master cylinder does not need to be full to the top. Over fill can be pushed out.

Thanks for posting man!! and I'll take a second look at that and make sure not to fill the new MC to full!
Thanks Boog!!!!

[Ironangel]

"Nearest Master Cylinder First"...Thats a quote from the Factory Service Manual...Even if the wrong way works, dont make it right..."'just sayin"

[jbassC10]

Originally Posted by Ironangel

"Nearest Master Cylinder First"...Thats a quote from the Factory Service Manual...Even if the wrong way works, dont make it right..."'just sayin"

Nice man!! Total belief in your statement the first time for sure! But I really appricate the time you took to look that up!
Others probably will begin to change their style up to do it the correct way now once they read this "blog" comments on here!
Later!

[Mock1]

Just posting this in case you dont know, and it hasnt been mentioned.
Its best to plug the outlets in the MC when bench bleeding it, and loosen the one your bleeding in the order ironangel specified. Also, its best to put the sytem under VACUUM when bleeding the lines, instead of pressure. That will PULL the air out of the system. Start from the farthest wheel cylinder, and work your way in.
One more thing, the factory proportion valve is more than likely clogged up. 86 that thing and get a new one. Wilwood sells them and they come with the light switch.

[jbassC10]

Originally Posted by Mock1

Just posting this in case you dont know, and it hasnt been mentioned.
Its best to plug the outlets in the MC when bench bleeding it, and loosen the one your bleeding in the order ironangel specified. Also, its best to put the sytem under VACUUM when bleeding the lines, instead of pressure. That will PULL the air out of the system. Start from the farthest wheel cylinder, and work your way in.
One more thing, the factory proportion valve is more than likely clogged up. 86 that thing and get a new one. Wilwood sells them and they come with the light switch.

Awesome! Thanks man!! I've got a new one. So will see what happens when i install it and bleed it correctly!!!
Thanks again!

[jbassC10]

Originally Posted by Mock1

Just posting this in case you dont know, and it hasnt been mentioned.
Its best to plug the outlets in the MC when bench bleeding it, and loosen the one your bleeding in the order ironangel specified. Also, its best to put the sytem under VACUUM when bleeding the lines, instead of pressure. That will PULL the air out of the system. Start from the farthest wheel cylinder, and work your way in.
One more thing, the factory proportion valve is more than likely clogged up. 86 that thing and get a new one. Wilwood sells them and they come with the light switch.

Okay thanks! I'm gonna go and get some bleeder lines at an auto part store here soon and see what i can do!! Thanks!

[chiefcfd]

Wow, I've bled brakes wrong my whole life. I have always started at the farthest point. Just the way I was taught. Thanks Ironangel, next time I might get it right.

[Mock1]

Dam, ive been doin it wrong this whole time.
No wonder I cant never get all the air out. Ironangel, thanks.
I gotta get a manual.
Is that a Haynes, or a service manual?