When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I've searched the forum and come up empty, but there was a thread discussing brake bleeding on C3s that included a great, a bit lengthy but very well written writeup by a guy who used to run a shop. He had a lot of good information about bleeding C3 brakes. I tried searching C3 brake bleeding and I tried retracing my original search and cannot find it. If anyone knows where this writeup is and can help. I'd appreciate it.
My story: 1969 without power brakes. I've been rebuilding the car for the last 18 months with a technician/friend. Bleeding the brakes was causing us difficulty. New MC, new proportioning valve, new calibers, new rotors, new brake lines, all with a goal of originality. Using a power bleeder, we finally got the brakes working but they're still a bit soft. They work, but if I needed to lock up the brakes, I don't think I could. I'm the owner/helper not the technician that's helping me so I cannot say if the rotor runout was checked or what it might be. I can pursue the runout issue, but at this point I was mostly interested if anyone might know the link to the excellent writeup about brake bleeding.
I've searched the forum and come up empty, but there was a thread discussing brake bleeding on C3s that included a great, a bit lengthy but very well written writeup by a guy who used to run a shop. He had a lot of good information about bleeding C3 brakes. I tried searching C3 brake bleeding and I tried retracing my original search and cannot find it. If anyone knows where this writeup is and can help. I'd appreciate it.
My story: 1969 without power brakes. I've been rebuilding the car for the last 18 months with a technician/friend. Bleeding the brakes was causing us difficulty. New MC, new proportioning valve, new calibers, new rotors, new brake lines, all with a goal of originality. Using a power bleeder, we finally got the brakes working but they're still a bit soft. They work, but if I needed to lock up the brakes, I don't think I could. I'm the owner/helper not the technician that's helping me so I cannot say if the rotor runout was checked or what it might be. I can pursue the runout issue, but at this point I was mostly interested if anyone might know the link to the excellent writeup about brake bleeding.
Thank you.
Common problem when you replace a MC in most cars. Worse on corvette's due to the angle of the MC.
Rotor runout can effect your braking, and should be something you check/fix regardless.
One thing I’ve found especially when using a power bleeder is that you have to crack the bleeders only very slightly to get the bubbles out. Opening them too far with pressure behind it keeps the velocity of the brake fluid too high, trapping bubbles in the lines and calipers. Cracking them just enough to get some fluid out while hitting the caliper with a rubber mallet has given me good results.
Another thing if you want to increase your braking force, power brakes!
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Two different size M/C's.
Power brakes have a 1 and 1/8" bore,
Manual M/C has a 1" bore.
Do you have the correct one?
Did you bench bleed the M/C?
M/C's have a deep or shallow hole, did the new match the old?
Is the new M/C good?
Remove one hard line and plug the hole and then remove the other line and test again, the pedal should be rock solid in both tests or the M/C is bad.
Check the 'gap' between the rod and the M/C, did you use this tool?
In the rear, did you bleed the outer bleed screw first then the inner?
As stated above, you can plug the side ports to isolate the master from the rest of the system for testing.
However, NEVER use a bolt to plug the port. You will damage the machined in cast iron, tapered flare inside.
If you want to test the masters pressure holding ability, two test lines will need to be fabricated.
Excessive rotor run-out or not, you should be able to get a firm brake pedal. Run-out piston air pumping is something that makes itself known after you put miles on the car.
As cagotzmann referred to: Have you tried lifting the rear of the car so the master is tilted at a slight downward angle and then bleeding the master? This will allow trapped air to move rearward to the MC's reservoir ports so it can escape.
Excessive rotor run-out or not, you should be able to get a firm brake pedal. Run-out piston air pumping is something that makes itself known after you put miles on the car.
As cagotzmann referred to: Have you tried lifting the rear of the car so the master is tilted at a slight downward angle and then bleeding the master? This will allow trapped air to move rearward to the MC's reservoir ports so it can escape.
No, we have not tried lifting the rear of the car. I will suggest that to the shop doing the work.
Rotor runout can effect your braking, and should be something you check/fix regardless.
One thing I’ve found especially when using a power bleeder is that you have to crack the bleeders only very slightly to get the bubbles out. Opening them too far with pressure behind it keeps the velocity of the brake fluid too high, trapping bubbles in the lines and calipers. Cracking them just enough to get some fluid out while hitting the caliper with a rubber mallet has given me good results.
Another thing if you want to increase your braking force, power brakes!
Thanks. I'll share this with the shop doing the work now.
Excessive rotor run-out or not, you should be able to get a firm brake pedal. Run-out piston air pumping is something that makes itself known after you put miles on the car.
As cagotzmann referred to: Have you tried lifting the rear of the car so the master is tilted at a slight downward angle and then bleeding the master? This will allow trapped air to move rearward to the MC's reservoir ports so it can escape.
We have not tried lifting the rear of the car but will suggest that to the shop owner where the car currently is..
1969 brake bleeding
