Another good fix. It is totally amazing how that small of a gap,,,,,II,,,, can screw up the brake pedal feel.
Brake bleeding & hair pulling
Le Mans Master
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From: Cool Northern Michigan
No-Can-Do on the video for me anyway.
So what is your plan on adding to the rod gap?
I will stick with my story of 0.060 or 1/16". And even that seems tight to me.
You have to have some play or you will have caliper pistons not allowed to retrieve back into their bore.
Its not the pistons job to push the brake pedal back up where it belongs, free wheeling.
So what is your plan on adding to the rod gap?
I will stick with my story of 0.060 or 1/16". And even that seems tight to me.
You have to have some play or you will have caliper pistons not allowed to retrieve back into their bore.
Its not the pistons job to push the brake pedal back up where it belongs, free wheeling.
Last edited by HeadsU.P.; May 6, 2022 at 09:25 PM.
Thread Starter
Instructor
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From: Missouri
Bearings are new and good. Wheel turns easily when the pedal travel is long. I removed the gasket to reduce the spacing between the rod and MC.
Try this link.
Wheel drag test
I know there should be some drag but just not sure on how much. Note I'm just turning with one hand and not really that hard but if y'all think it's too much, I'll add a small amount of spacing to enlarge the rod gap but ultimately, I think that's the culprit of my issue.
Try this link.
Wheel drag test
I know there should be some drag but just not sure on how much. Note I'm just turning with one hand and not really that hard but if y'all think it's too much, I'll add a small amount of spacing to enlarge the rod gap but ultimately, I think that's the culprit of my issue.
Le Mans Master
Joined: Jun 2019
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From: Loveland
It is good to understand how the MC works. There are small holes from each reservoir, front and rear, into the bore. The seals start a bit back from these small holes. There isn't any pressure created to the calipers from the MC until the seals are pushed past the small holes. You can look into the reservoir holes and see when the seals pass the little hole. The only way you can create pressure to the calipers is if the seals are covering the holes with the pedal fully retracted. Get a light and watch your little hole, then have someone push the pedal about 1/2 inch.
Le Mans Master
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From: Loveland
I looked at both the holes in the bottom of each reservoir. There is a very small one and a larger one. With the pedal fully retracted, I can just see the rear edge of the seal in the larger hole. As soon as the pedal is pressed I can see the seal start to move. If you look very close you can then see the seal move under the little hole. The piston in the MC will not start creating any pressure until it passes the small hole. It seems to me that this would prevent any premature pressure to the calipers as long as the seal retracts past the little hole. You can see in this diagram that the piston would have to be pushed in a long way before pressure would build in the lines to the calipers. Also if the rod from the pedal has an excessive gap, the pedal moves before pushing on the MC piston.
Last edited by kodpkd; May 7, 2022 at 08:23 PM.
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From: Missouri
Ok I checked the ports like you mentioned and it looked good. I also checked the mounted MC against the old one and the piston locations looked the same. Went for a test drive and the pedal is way better now. I haven’t had time to check again for any weeping but I believe we have figured out the issue and it was that MC spacing creating too much space between the rod and the MC. Thanks for all the help fellas. Thought I’d never figure this one out.
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Thread Starter
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From: Missouri
Exactly. That gap is pretty critical. I’m sure being old some of that gap probably enlarged a little due to wear over time plus the aforementioned gasket. Hopefully there’s no more weeping which I’ll check today. But we are off and running finally!
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From: Missouri
I think someone put that on. There’s no reason I can see for a gasket there as the MC is sealed. The service manual shows something that looks like a round foam gasket but that would not sit on the mounting surface and mine didn’t have one. It just had a gasket on the mounts.
Le Mans Master
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From: Loveland
Something else I read about cleaning calipers and MC's. Do NOT use brakleen on any of the rubber seals or parts. It will soften the rubber. Clean everything else with brakleen, then dry it off really well, and then use brake fluid to rebuild everything.
Last edited by kodpkd; May 8, 2022 at 01:34 PM.
Drifting
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From: Baton Rouge, Louisiana, metro area
I think someone put that on. There’s no reason I can see for a gasket there as the MC is sealed. The service manual shows something that looks like a round foam gasket but that would not sit on the mounting surface and mine didn’t have one. It just had a gasket on the mounts.
If so, do you make road trips? You the go-to source on 80’s Corvette brake systems now!
Le Mans Master
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From: Loveland
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From: Missouri
Yeah it’s definitely not the bleeder. From the pattern it looks like the piston but I’ll need to pull the wheel off and the pads and take a closer look. But yes, brakes are working finally! Many thanks to all of y’all for helping me figure this out.
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I know they’ll swap it but just means more work on these dang brakes.
Thread Starter
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From: Missouri