No Brakes 75 Corvette
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 2,297
Likes: 156
From: Clayton New Jersey
No Brakes 75 Corvette
Hello,
I hope somebody can help with this one. 1975 Corvette, I have replaced the master cylinder, I did bench bleed it, all 4 calipers with pads and the 2 front rubber lines. I also had to replace the metal line on the drivers front. I have bleed these things over and over. I'm not getting any air all fluid and I still have no pedal. The rod coming out of the brake booster looks like someone had been messing with that at one time. Any help would be great.
Thanks, Bill
I hope somebody can help with this one. 1975 Corvette, I have replaced the master cylinder, I did bench bleed it, all 4 calipers with pads and the 2 front rubber lines. I also had to replace the metal line on the drivers front. I have bleed these things over and over. I'm not getting any air all fluid and I still have no pedal. The rod coming out of the brake booster looks like someone had been messing with that at one time. Any help would be great.
Thanks, Bill
Burning Brakes
Joined: May 2008
Posts: 860
Likes: 0
From: Stratford Ontario
A couple other things You can check is that the rod pushing the shaft in master cylinder is the correct size as there is two different sizes. Also if Your brake booster isnt holding vacum because of check valve or seal leaking Your brakes wont work.
Intermediate
Joined: Nov 2009
Posts: 35
Likes: 0
From: Lancaster SC
Just changed my master on a76 and brakes aren't as firm as they should be. Was also wondering about the adjustment on the push rod going into the master. Service manual doesn't mention anything about how it should be adjusted. Anyone know how far out the end of that push rod should be adjusted? I have about an inch of thread showing and you could feel the master cylinder piston going in as I tightend it up to the booster. Thanks.
Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Just changed my master on a76 and brakes aren't as firm as they should be. Was also wondering about the adjustment on the push rod going into the master. Service manual doesn't mention anything about how it should be adjusted. Anyone know how far out the end of that push rod should be adjusted? I have about an inch of thread showing and you could feel the master cylinder piston going in as I tightend it up to the booster. Thanks.
Intermediate
Joined: Nov 2009
Posts: 35
Likes: 0
From: Lancaster SC
The master is same as the one I took off, where the rod goes inside the back of the piston about an inch or so. Was given a used rebuilt master with only the dimple at the back of the piston (shorter rod) and knew I needed the one where the rod actually goes into the piston that inch and some. Ordered it for a power brake car and the numbers were the same as the original one I took off. Am just surprised that the service manual made no mention of the adjustment of the push rod. Since I felt the rod pushing in the piston as I tightened the master to the booster, probably about an inch, I'm thinking that I'm not getting enough stroke on the piston as it's adjusted now. Will loosen it and adjust the rod tip so that it just touches the piston as the master is getting tight against the booster with just a bit of compression of the piston and see what I get as far as pedal pressure. Thanks for the responses everyone.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
The 75 and 76 take the deep piston master as you described.
To adjust the rod, with the pedal all the way up (booster should do that), make sure there is just a hairline space between the master flange and the booster flange. You really don't want to move the piston at all.
If you don't want to remove the lines from the cylinder, you can remove the two mounting bolts on the combo valve below and you will be able to carefully remove the master to gain access to the rod adjustment.
While it's off, you may want to check the bore size of the master to make sure it's 1-1/8". I looked at one misboxed a couple weeks ago and the 1" manual master will give a very low pedal.
Or, it's wise also to put plugs in the new master ports after installed instead of the lines to test for air and internal leakage. Saves some guessing later.
To adjust the rod, with the pedal all the way up (booster should do that), make sure there is just a hairline space between the master flange and the booster flange. You really don't want to move the piston at all.
If you don't want to remove the lines from the cylinder, you can remove the two mounting bolts on the combo valve below and you will be able to carefully remove the master to gain access to the rod adjustment.
While it's off, you may want to check the bore size of the master to make sure it's 1-1/8". I looked at one misboxed a couple weeks ago and the 1" manual master will give a very low pedal.
Or, it's wise also to put plugs in the new master ports after installed instead of the lines to test for air and internal leakage. Saves some guessing later.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Burning Brakes
Joined: Jan 2002
Posts: 935
Likes: 0
From: Trumbull CT.
This is a copy and paste but you do need the correct clearance before you bleed your brakes. I finally broke down and bought a power bleeder.
"The pushrod that actuates the master cylinder must be properly adjusted. Ideally there should be only slight clearance between the booster pushrod and the master cylinder pushrod. Interference will preload the master cylinder. When the system is preloaded, it builds pressure each time the pedal is pressed. Since the master cylinder is not allowed to fully release the pressure from the previous stroke, the system will eventually lock the wheels. Too much clearance will cause excessive freeplay in the pedal.
"The pushrod that actuates the master cylinder must be properly adjusted. Ideally there should be only slight clearance between the booster pushrod and the master cylinder pushrod. Interference will preload the master cylinder. When the system is preloaded, it builds pressure each time the pedal is pressed. Since the master cylinder is not allowed to fully release the pressure from the previous stroke, the system will eventually lock the wheels. Too much clearance will cause excessive freeplay in the pedal.
