I'm on my 2nd new Brakebest select NMC11317
I actually have a AC delco in route because I like to throw many at issues till it's fixed lol
new brake system no pressure to the rear calipers
- Thread starter Rlamas87
- Start date
I actually have a AC delco in route because I like to throw many at issues till it's fixed lol
Im not familiar with that part number. What's the application? What's the piston size?
I found the 1" piston works best. I am using a master for a 1980 Buick Riviera with 4 wheel discs.
oh I'm not 100% sure on the piston size.. I ordered it as a 87 buick regal.. did the same for the AC delco but just expecting it to be a better quality?
I will say when I bench bled the MC I pulled out the line that feeds the rear calipers and notice it had a weak flow?
The piston in the stock 78-88 A/G bodies with disc/drum and vacuum brakes is 7/8". My experience is this results in a long travel and low brake pedal when trying to stop even with the system properly bled. You need a master with a 1" piston....as mentioned, the 80 Buick Riviera OR you even try finding a 98-04 Blazer master.....I think you need to find one for right hand drive vehicles as they have the lines on the same side as the A/G body master
You mentioned 2 terrible words in one sentence..., O'Reilly's and Master Cylinder. However; your cylinder is new?? I no longer do "rebuilt"... Too many problems.
If you have a helper... Have him/her open the bleeders and put rag on top of each... Mash the brake pedal to the firewall quickly and firmly and hold. Close the open bleeders.
If you have a helper... Have him/her open the bleeders and put rag on top of each... Mash the brake pedal to the firewall quickly and firmly and hold. Close the open bleeders.
Your master cylinder needs to be rebled almost for sure. And the stock master is tool small for what you’re attempting. I used the same one that gnvair is recommending with the same rear brake kit you have and C6 fronts. With the stocker it wouldn’t move enough fluid to bleed the rears and after two days of gravity bleeding and getting the rears working the pedal was so deep that it made my butthole pucker for any aggressive brake applications.
Get the 80 Riv MC and you’ll be good.
Get the 80 Riv MC and you’ll be good.
Sorry missed part where you replaced all lines. Procedure I mentioned was not to make a mess but to quickly raise line pressure to dislodge dirt/crud etc..., left in lines. From there you go back to normal bleeding procedure. If you are gravity bleeding and no flow, you have to fix that first.
Yours will never work with current part selection. Basically you have the wrong Master Cylinder. You purchased a disc/drum MC and you need a disc/disc MC.
As others stated your front bore is 1.42" (26mm) and your rear bore is .93" (23mm). Plus the rear reservoir is way too small and will never work. It doesn't hold enough fluid to properly actuate the caliper piston(s).
Disc needs about 900 psi and drum about 500 psi (there or about). So as you currently experience..., low or no flow volume and no/low pressure to the rear.
Your current system will lock the front while the rear will barely engage causing dangerous possibility to spin or loss of control during panic stop.
There is a section of Hottroders Forum, Crank Shaft Coalition where I wrote about brakes.
Work with your local parts store. Cross Reference NM1740 AutoZone is the disc front/disc rear MC. I couldn't find the O'Reilly number, their site kept crashing.
Maybe try 80/81 Turbo Trans Am or similar.
Yours will never work with current part selection. Basically you have the wrong Master Cylinder. You purchased a disc/drum MC and you need a disc/disc MC.
As others stated your front bore is 1.42" (26mm) and your rear bore is .93" (23mm). Plus the rear reservoir is way too small and will never work. It doesn't hold enough fluid to properly actuate the caliper piston(s).
Disc needs about 900 psi and drum about 500 psi (there or about). So as you currently experience..., low or no flow volume and no/low pressure to the rear.
Your current system will lock the front while the rear will barely engage causing dangerous possibility to spin or loss of control during panic stop.
There is a section of Hottroders Forum, Crank Shaft Coalition where I wrote about brakes.
Work with your local parts store. Cross Reference NM1740 AutoZone is the disc front/disc rear MC. I couldn't find the O'Reilly number, their site kept crashing.
Maybe try 80/81 Turbo Trans Am or similar.
Last edited:
Try bleeding the fronts see if that helps. I did the blazer/s10 brakes same problem turned out the front needed to be bleed first .
Several thoughts:
1. Don't know what type of prop valve you installed BUT when I was buying parts to make this same upgrade, I almost bought the wrong valve. Because I was ultimately upgrading/converting to disc in rear, I asked for front disc with rear drum version. I was not focused and thinking that the new setup would be a discs all around. Lucky for me, the OPGI counter guy recognized what I was doing and told me I needed a disc-disc proportioning valve. What did you install?
2. The normal/usual way of bleeding brakes is to start with the brakes that are farthest away from the master cylinder. That makes the order: passenger rear, driver rear, passenger front, and lastly driver front brakes. This is a tried and true order.
3. Although there are many new fan-dangled tools to accomplish brake bleeding single-handed, nothing works better than having a partner to pump and hold the brake pedal while you open, watch, and close the bleeder valves. My neighbor and I usually do 3 cycles of slowly pumping the pedal 10 times, then holding all the while watching for any air bubbles in a clear plastic tube collecting brake fluid into a glass jar.
4. Once bleeding is completed, do a test drive. If it doesn't feel good, do the WHOLE process again! Remember, this is the system that will bring your ride to a stop after you launch it down the street!
5. Lastly, PATIENCE is paramount! This is a hobby and should be enjoyable!
Good luck!
1. Don't know what type of prop valve you installed BUT when I was buying parts to make this same upgrade, I almost bought the wrong valve. Because I was ultimately upgrading/converting to disc in rear, I asked for front disc with rear drum version. I was not focused and thinking that the new setup would be a discs all around. Lucky for me, the OPGI counter guy recognized what I was doing and told me I needed a disc-disc proportioning valve. What did you install?
2. The normal/usual way of bleeding brakes is to start with the brakes that are farthest away from the master cylinder. That makes the order: passenger rear, driver rear, passenger front, and lastly driver front brakes. This is a tried and true order.
3. Although there are many new fan-dangled tools to accomplish brake bleeding single-handed, nothing works better than having a partner to pump and hold the brake pedal while you open, watch, and close the bleeder valves. My neighbor and I usually do 3 cycles of slowly pumping the pedal 10 times, then holding all the while watching for any air bubbles in a clear plastic tube collecting brake fluid into a glass jar.
4. Once bleeding is completed, do a test drive. If it doesn't feel good, do the WHOLE process again! Remember, this is the system that will bring your ride to a stop after you launch it down the street!
5. Lastly, PATIENCE is paramount! This is a hobby and should be enjoyable!
Good luck!
The problem with bleeding the fronts first is that the piston for the rear wheels requires bottoming the pedal on the floor. You will not be able to get full travel and move that piston if you bleed the fronts first.
Similar threads
