Soft brake pedal
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
The only way I can see this happening, is if your MC has a so much rust inside the bore, that the seal catches on the rust ridge. If there is that much rust inside the bore maybe it should be replaced. OR if the MC has a small bolt inside the bore that stops the piston from moving to far, I haven't seen this in a C3 MC.
What's happening here is, when bench bleeding, you are pushing the screwdriver / piston in farther than the MC is designed for. In other words there are no normal stops.
On the vehicle, there are stops to prevent over extending the piston. Its called the floorboard.
The brake pedal assembly is not only changing the amount of force delivered to the MC, but also changes the stroke length when compared to a MC in a bench vise.
The term: "you will damage the seals" over extending may not be the best statement. The "O" rings will roll-over in the bore on the return stroke with the screwdriver., making it useless. Can it be repaired? Sure. The piston is good, the bore is good. The "O" Ring? Not so good.
Last edited by HeadsU.P.; Jun 14, 2021 at 09:50 AM.
Le Mans Master
Joined: Jun 2019
Posts: 5,452
Likes: 2,168
From: Loveland
Here is the inside of the MC from my C3. It is the same as 2 other pistons from 2 other MC's. All I see is 5 lip seals. There are no O rings to turn over. The bore is perfectly smooth all the way to the end. You can see the rod on the end that limits the travel of the piston. Maybe there are different pistons that fail easier. Probably not as good.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
IDK.
I am going by what Lone Star told me.
And I am going by, my very first incorrectly done bench bleeding process: fail.
Meanwhile, I will continue to warn people about the possible damage done while bench bleeding if not careful.
I am going by what Lone Star told me.
And I am going by, my very first incorrectly done bench bleeding process: fail.
Meanwhile, I will continue to warn people about the possible damage done while bench bleeding if not careful.
Last edited by HeadsU.P.; Jun 14, 2021 at 07:57 PM.
Instructor
Joined: May 2021
Posts: 127
Likes: 28
I went through the same situation not long ago. Without doubt, you have air in the system. It is extremely hard to get it all out. It took me quite a number of tries, even with a pressure bleeder.
I finally ended up with a so-so brake pedal which got me through an inspection for the title transfer.
But, the only way I found to get rid of all the air was to bleed the brakes backwards. I will post a description and a couple of pictures tomorrow. Everybody will think I'm crazy, but it worked.
Stay tuned.
I know it seems hopeless, it sure did to me, but you will get there, and believe me, it's worth it, I've never, in fifty years, had a car that was more fun to drive.
I finally ended up with a so-so brake pedal which got me through an inspection for the title transfer.
But, the only way I found to get rid of all the air was to bleed the brakes backwards. I will post a description and a couple of pictures tomorrow. Everybody will think I'm crazy, but it worked.
Stay tuned.
I know it seems hopeless, it sure did to me, but you will get there, and believe me, it's worth it, I've never, in fifty years, had a car that was more fun to drive.
Le Mans Master
Joined: Jun 2019
Posts: 5,452
Likes: 2,168
From: Loveland
What would help Corvette people here, would be to figure out why some MC's don't have a problem pushing the cylinder all the way in and others seem to have issues. There has to be differences.
