Question about C3 master cylinder flow
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,594
Likes: 7,041
From: New Or-leens Loo-z-anna
As another member suggested....remove the seal assembly from the MC and verify that the seal hasn't "rolled over" . If yoy are really brave, reinstall the seal asembly and push it all the way into the MC bore about 20 times....remove it again to see if it/seal WILL toll over.
"Bleeding Vette brakes is much like resuscitating an unconscious Grizzly bear".
I hope you find the problem.
"Bleeding Vette brakes is much like resuscitating an unconscious Grizzly bear".
I hope you find the problem.
Racer
Joined: Apr 2009
Posts: 331
Likes: 44
From: Cincinnati Ohio
I may have missed something here, but you are installing a Corvette Master Cylinder on a pick-up truck. The Corvette has disc brakes all around and a lot trucks are Disc/Drum. There is different MC for each application as well as between manual and power brakes.
Le Mans Master
Joined: Jun 2019
Posts: 5,470
Likes: 2,179
From: Loveland
Do you have a Motive bleeder? I think you can bleed the brakes useing the two person method,,,, open close open close etc, but the Motive bleeder does make bleeding easier. I think positive pressure from the MC is the best way to bleed.
Last edited by kodpkd; Sep 7, 2021 at 04:36 PM.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
It seems you guys are missing perhaps the most important point.
One absolutely will not get all the air out of a C3 master unless it is bled
1-off the car
2-rotated so that the pressure ports are at 12 o'clock, They are drilled at about 11 o'clock leaving space above it for air. One must rotate it. A pressure bleeder on the bench works well.
You can see that in the pic.
Another good hint to to handle the fluid very gently, it easily gets tiny air bubbles when poured or moved around in a normal manner.
These tiny bubbles later merge into bigger ones and even so leave a lot of compressible air in the system.
I also posted how to easily convert to a 1.25" master to raise the applied brake pedal.
You'll have to search for that thread if desired.
One absolutely will not get all the air out of a C3 master unless it is bled
1-off the car
2-rotated so that the pressure ports are at 12 o'clock, They are drilled at about 11 o'clock leaving space above it for air. One must rotate it. A pressure bleeder on the bench works well.
You can see that in the pic.
Another good hint to to handle the fluid very gently, it easily gets tiny air bubbles when poured or moved around in a normal manner.
These tiny bubbles later merge into bigger ones and even so leave a lot of compressible air in the system.
I also posted how to easily convert to a 1.25" master to raise the applied brake pedal.
You'll have to search for that thread if desired.
Le Mans Master
Joined: Jun 2019
Posts: 5,470
Likes: 2,179
From: Loveland
I agree about bench bleeding the MC at bifferent angles like you said. But there is still a chance air will get into the MC between when you remove the bleed tubes and hooking up the lines on the car. Once the MC is on the car you can still get the last bit of air out by raising the rear of the MC so it is higher that the front. The holes from the bore to the reservoir are open to let air escape. With the reservoirs full of fluid, you can see into the bore from the reservoirs. You can even watch the seals move past the holes as Autocommon said.
What do you mean switch to a 1.25" to raise the applied pedal? A larger bore will give you more fluid flow but less pressure at the calipers for a given pedal force. Large bore is good for power brakes, small for manual brakes.
What do you mean switch to a 1.25" to raise the applied pedal? A larger bore will give you more fluid flow but less pressure at the calipers for a given pedal force. Large bore is good for power brakes, small for manual brakes.
Last edited by kodpkd; Sep 7, 2021 at 04:40 PM.
Thread Starter
Cruising
Joined: Aug 2021
Posts: 11
Likes: 1
So I'm giving up. Yes it's on a truck, a 72 Jeep wagoneer with a Cummins/Onan 6A diesel swap. It's got a hydro boost with 4 wheel disc brakes, calipers are all matching from the front of a C10 truck. This is why they had used a C3 master cylinder for disc disc. And the C3 master is why I posted in a better forum.
I'm tired of this BS with this master. I honestly don't have the time to deal with it any more, and the next owner if they have issues with it/bleeding the system...it's not worth it. I'm gonna drop the $200 and put a wilwood on it and be done.
I do appreciate all the info here, I'm sure if I spent more time with it I could eventually get it bled, but I've got sh*t to do lol. I need the brakes to just be done, period. Thanks again guys!
Mark
I'm tired of this BS with this master. I honestly don't have the time to deal with it any more, and the next owner if they have issues with it/bleeding the system...it's not worth it. I'm gonna drop the $200 and put a wilwood on it and be done.
I do appreciate all the info here, I'm sure if I spent more time with it I could eventually get it bled, but I've got sh*t to do lol. I need the brakes to just be done, period. Thanks again guys!
Mark
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
I agree about bench bleeding the MC at bifferent angles like you said. But there is still a chance air will get into the MC between when you remove the bleed tubes and hooking up the lines on the car. Once the MC is on the car you can still get the last bit of air out by raising the rear of the MC so it is higher that the front. The holes from the bore to the reservoir are open to let air escape. With the reservoirs full of fluid, you can see into the bore from the reservoirs. You can even watch the seals move past the holes as Autocommon said.
What do you mean switch to a 1.25" to raise the applied pedal? A larger bore will give you more fluid flow but less pressure at the calipers for a given pedal force. Large bore is good for power brakes, small for manual brakes.
What do you mean switch to a 1.25" to raise the applied pedal? A larger bore will give you more fluid flow but less pressure at the calipers for a given pedal force. Large bore is good for power brakes, small for manual brakes.
Easiest to remove the temporary plug from the port and connect each line separately before mounting the master to the booster etc. You do use temp plastic plugs in the ports I hope.
Then either pressure bleed or 2 person bleed properly or gravity bleed. No air will be sucked back in.
For the larger bore just google my old posts as I mentioned, it raises the pedal.
Le Mans Master
Joined: Jun 2019
Posts: 5,470
Likes: 2,179
From: Loveland
The different bore MC's on the corvette are exactly the same, except for the bore size. By increasing the bore size, this doesn't do a thing to the pedal throw. I do agree that when you use a bigger bore MC,,,,, you,, need to increase the travel of the pedal to get proper brake pressure. But this is something that you need change. This is a mistake that is made many times when installing the wrong MC. The vet has two holes in the pedal lever that needs to be correct depending what MC you have.
The info about air getting into the MC is for info only. It happes very often. Not everyone is experienced with bleeding and then installing the MC. Is only a caution note.
I don't use plastic plugs,,, I keep the original bleeder hoses hooked up untill the MC is in place for the brake lines.
This does make me wonder it the pedal travel in the truck isn't enough to make the vet MC work properly. If the vet MC requires 4 inches of travel to reach full pressure and the truck pedal only has 3 inches untill it bottoms out, this would cause the entire system not to pressurize correctly.
The info about air getting into the MC is for info only. It happes very often. Not everyone is experienced with bleeding and then installing the MC. Is only a caution note.
I don't use plastic plugs,,, I keep the original bleeder hoses hooked up untill the MC is in place for the brake lines.
This does make me wonder it the pedal travel in the truck isn't enough to make the vet MC work properly. If the vet MC requires 4 inches of travel to reach full pressure and the truck pedal only has 3 inches untill it bottoms out, this would cause the entire system not to pressurize correctly.
Last edited by kodpkd; Sep 7, 2021 at 09:30 PM.
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Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
You have it backwards about the pedal travel with the bigger MC bore.
I've done it several times.
A low pedal is a common complaint on a power car and the only reason I even mentioned it is because it helps a bunch with that.
You can use the info for what it is or not. Just trying to help a bit.
I've done it several times.
A low pedal is a common complaint on a power car and the only reason I even mentioned it is because it helps a bunch with that.
You can use the info for what it is or not. Just trying to help a bit.