Help! Brake still isn't working!

[Dr. Squishy]

I recently bought my '73 Stingray and had to replace the brake calipers. After a small mishap that ended with a cracked bumper :ugh I bled the brakes again and ended up with a firm pedal. My brother and I tested the brakes by spinning the wheels while the car was still on the lift, and three of the wheels were gripped really firmly by the new calipers. However; the front right wheel was gripped, but not even enough to stop me from spinning it by hand. We bled it again to the same end: still not gripped hard enough. I'm going to borrow a pressure bleeder from a friend and try that, but does anyone know if I'm barking up the wrong tree? I'd appreciate any advice.
Thanks,
Dr. Squishy

 

[the boss]

Have found any kind of contamination in the brake fluid before you replace the calipers? This can be seen most of the time in the master cylinder covert, the rubber gasket for the cover get inflated. If there was, you may end up replacing every pieces on the hydrolic brake systeme that have rubber in it like hose, master cylinder, proportionning valve (if there is ), flushing all the lines
After bleeding the brakes, and having some wheels very stiff, did you tried to open a bleeder screw on one of those stiff wheel to see if there where residual pressure? If pressure goes out and the wheel get free you will have to pump the brakes until the wheel get stiff again then open the brake line closer to the master to try to locate where the pressure is keept in the line.
If residual pressure comes from the master cylinder check for an ajustable rod between the master and booster. I saw a few time car owner, whit a low pedale issue, trying to adjust that rod to raise the pedale and get in a position like they where putting a light pressure on the brake pedale. If you tried to adjust that rod, scratch a mark and count the numbers of turn you do so if that was not the probleme, you can put it back at the same position
To be honest, I never work on a car like your's but as a mecanic the basics are the same.
Good luck Stephane

 

[TimAT]

I'd be looking at the flex lines to the calipers too. They have been known to fail and either balloon when pressure is applied or internally fail and can block the fluid flow either way. Remember- the youngest C3 is still 30 years old.

 

[glen242]

I recently bought my '73 Stingray and had to replace the brake calipers. After a small mishap that ended with a cracked bumper :ugh I bled the brakes again and ended up with a firm pedal. My brother and I tested the brakes by spinning the wheels while the car was still on the lift, and three of the wheels were gripped really firmly by the new calipers. However; the front right wheel was gripped, but not even enough to stop me from spinning it by hand. We bled it again to the same end: still not gripped hard enough. I'm going to borrow a pressure bleeder from a friend and try that, but does anyone know if I'm barking up the wrong tree? I'd appreciate any advice.
Thanks,
Dr. Squishy

Rather than using a pressure bleeder, I use Speed Bleeders (all 6 of them) and have had excellent results.

6 Speed Bleeders are quite a bit cheaper than a power (Motive) bleeder.

 

[WHEELS 81]

brake bleeding

I recently bought my '73 Stingray and had to replace the brake calipers. After a small mishap that ended with a cracked bumper :ugh I bled the brakes again and ended up with a firm pedal. My brother and I tested the brakes by spinning the wheels while the car was still on the lift, and three of the wheels were gripped really firmly by the new calipers. However; the front right wheel was gripped, but not even enough to stop me from spinning it by hand. We bled it again to the same end: still not gripped hard enough. I'm going to borrow a pressure bleeder from a friend and try that, but does anyone know if I'm barking up the wrong tree? I'd appreciate any advice.
Thanks,
Dr. Squishy

Check condition of brake hoses if worn replace(swollen). A piece of material from the inside of an old hose could be causing poor closing of that caliper. Check entire brake line you have have a loose connection on that side. If all of this is a-ok then break open line at its high pont connections retighten and bleed. You may have a bubble on that side. Can't remember if this vehicle has proportioning valve or metering but usually these are a good place for air in the line aka bubbles to accumulate. Just crack it open , retighten and bleed. Good luck