Soft pedal after bleeding brakes
Burning Brakes
Joined: Sep 2018
Posts: 1,002
Likes: 410
Are you pumping the pedal and holding while someone cracks the bleeders?
IF SO does the pedal ever get hard when pumping and holding?
OR
Or are you using a mighty vac at the calipers?
Using a jar with a J tube and then pumping the pedal
Or using a 1": thick plexiglass plate drilled and tapped for a vacuum pump - rubber bead seal over the top of the MASTER CYLINDER - drawing a few atmospheres and pulling all the air from every point in the system?
IF SO does the pedal ever get hard when pumping and holding?
OR
Or are you using a mighty vac at the calipers?
Using a jar with a J tube and then pumping the pedal
Or using a 1": thick plexiglass plate drilled and tapped for a vacuum pump - rubber bead seal over the top of the MASTER CYLINDER - drawing a few atmospheres and pulling all the air from every point in the system?
Thread Starter
Navigator
Joined: Sep 2019
Posts: 9
Likes: 0
I was the one cracking open the bleeder so not sure, would have to ask my father and let you know tomorrow if the pedal was hard when he was holding it down to the floor. I was just using a clear tube over the valve to see when there were no more bubbles.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
try bleeding backwards. push pistons back into calipers. without opening any lines or bleeders. it will push fluid back up to the master. you may have a bubble in the proportioning valve or somewhere else up high.
Is my vette stock?? HAHA
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
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When I first got my car I had to bleed the brakes on multiple occasions to get a firm pedal. I think it took 4 tries
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Are you pumping the pedal and holding while someone cracks the bleeders?
IF SO does the pedal ever get hard when pumping and holding?
OR
Or are you using a mighty vac at the calipers?
Using a jar with a J tube and then pumping the pedal
Or using a 1": thick plexiglass plate drilled and tapped for a vacuum pump - rubber bead seal over the top of the MASTER CYLINDER - drawing a few atmospheres and pulling all the air from every point in the system?
IF SO does the pedal ever get hard when pumping and holding?
OR
Or are you using a mighty vac at the calipers?
Using a jar with a J tube and then pumping the pedal
Or using a 1": thick plexiglass plate drilled and tapped for a vacuum pump - rubber bead seal over the top of the MASTER CYLINDER - drawing a few atmospheres and pulling all the air from every point in the system?
Well there's a new method. Wouldn't that suck all the brakefluid out too?
The plexiglass plate you mentioned to seal the MC is for a Motive Pressure method. Not vacuum.
See my profile photo album: brake bleeding.
You will never get anywhere bleeding the system backwards.
Tech Contributor
Joined: Aug 1999
Posts: 15,177
Likes: 3,995
From: Connecticut, USA
Your 74 brake system is pretty basic yet pretty damn good once correctly setup. I suspect you have air in the system vs a leak since you have been around the car and would have seen a leak so the method of bleeding is suspect as the others mentioned.
When I was a kid of 18 with my 67 and my buddy had a 68 we would bleed his car every Saturday before going out driving. He didn't have leaks he had excessive rotor runout and bearing endplay. We didn't know any better at the time and did the 2 man method which works great if done correctly.
What I would do if I was working on this car would be
1- check for leaks
2- check rotor runout you want it under 005 but I set them to under 003"
3- check brake fluid, this should not be an issue since you have bled the car already
4- Look at the rubber hoses, if they are over 8 years old or unknown I would replace them
5- Check bearing endplay, less likely your issue since excessive endplay shows up before the brake issue
6- If the MC ran dry prior to brake work I would remove and bench bleed it.
7- Don't mix DOT rated brake fluids
8- Assemble anything removed/replaced and with the bled MC installed bleed the system again, RR, LR, RF, LF. I use a motive now and it's worth every penny. 2 man works as well but you have to work as a team or you will be fighting yourselves. I don't like a vaccum for this system, I know others like them but the ones I tried never worked as well as the others. I have also made an aluminum plate to cover the M/C and use low PSI air to make a power bleeder. It works but you have to keep an eye on the BF level and be very careful to repressurize it or you will get BF everywhere. I put it in the back of my box when I bought the Motive. Your circuits goes from the M/C through the pressure switch to each caliper. Pretty simple. The front calipers use a one-time copper washer between the hose and caliper- if you lost it or didn't replace it you will draw in air there or have a leak.
If the pedal goes to the floor you have a leak. The Motive allows you to pump up to 12-15 psi and watch the gauge on it. If it drops you have a leak and that won't show up with the other methods. I had a very small leak at a nut on new SS brake lines that didn't show up until I had the Motive.
When I was a kid of 18 with my 67 and my buddy had a 68 we would bleed his car every Saturday before going out driving. He didn't have leaks he had excessive rotor runout and bearing endplay. We didn't know any better at the time and did the 2 man method which works great if done correctly.
What I would do if I was working on this car would be
1- check for leaks
2- check rotor runout you want it under 005 but I set them to under 003"
3- check brake fluid, this should not be an issue since you have bled the car already
4- Look at the rubber hoses, if they are over 8 years old or unknown I would replace them
5- Check bearing endplay, less likely your issue since excessive endplay shows up before the brake issue
6- If the MC ran dry prior to brake work I would remove and bench bleed it.
7- Don't mix DOT rated brake fluids
8- Assemble anything removed/replaced and with the bled MC installed bleed the system again, RR, LR, RF, LF. I use a motive now and it's worth every penny. 2 man works as well but you have to work as a team or you will be fighting yourselves. I don't like a vaccum for this system, I know others like them but the ones I tried never worked as well as the others. I have also made an aluminum plate to cover the M/C and use low PSI air to make a power bleeder. It works but you have to keep an eye on the BF level and be very careful to repressurize it or you will get BF everywhere. I put it in the back of my box when I bought the Motive. Your circuits goes from the M/C through the pressure switch to each caliper. Pretty simple. The front calipers use a one-time copper washer between the hose and caliper- if you lost it or didn't replace it you will draw in air there or have a leak.
If the pedal goes to the floor you have a leak. The Motive allows you to pump up to 12-15 psi and watch the gauge on it. If it drops you have a leak and that won't show up with the other methods. I had a very small leak at a nut on new SS brake lines that didn't show up until I had the Motive.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Very well written. Good advice.
I like my Motive tank but the adaptor plate to cover the MC with chains and all, is a joke. And I think that plate design, leaking everywhere is what scared off potential buyers. That, and the cost.
Now that I made my own MC cover plate, its the only way to fly. I pour two bottles of DOT3 in the Motive tank, pump up to about 15 lbs and away you go.
For those that do brake jobs a lot, check eBay for a used Motive tank. May have to buy new hose, but wash it out real good w/ denatured alcohol, fabricate a MC plate and you are off to the races.
If you have to bleed just one caliper, then I prefer the Vac method.
I like my Motive tank but the adaptor plate to cover the MC with chains and all, is a joke. And I think that plate design, leaking everywhere is what scared off potential buyers. That, and the cost.
Now that I made my own MC cover plate, its the only way to fly. I pour two bottles of DOT3 in the Motive tank, pump up to about 15 lbs and away you go.
For those that do brake jobs a lot, check eBay for a used Motive tank. May have to buy new hose, but wash it out real good w/ denatured alcohol, fabricate a MC plate and you are off to the races.
If you have to bleed just one caliper, then I prefer the Vac method.
Last edited by HeadsU.P.; Sep 22, 2019 at 10:31 AM.
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Le Mans Master
Joined: Mar 2004
Posts: 7,502
Likes: 1,510
From: Little Rock AR
Very well written. Good advice.
I like my Motive tank but the adaptor plate to cover the MC with chains and all, is a joke. And I think that plate design, leaking everywhere is what scared off potential buyers. That, and the cost.
Now that I made my own MC cover plate, its the only way to fly. I pour two bottles of DOT3 in the Motive tank, pump up to about 15 lbs and away you go.
For those that do brake jobs a lot, check eBay for a used Motive tank. May have to buy new hose, but wash it out real good w/ denatured alcohol, fabricate a MC plate and you are off to the races.
If you have to bleed just one caliper, then I prefer the Vac method.
I like my Motive tank but the adaptor plate to cover the MC with chains and all, is a joke. And I think that plate design, leaking everywhere is what scared off potential buyers. That, and the cost.
Now that I made my own MC cover plate, its the only way to fly. I pour two bottles of DOT3 in the Motive tank, pump up to about 15 lbs and away you go.
For those that do brake jobs a lot, check eBay for a used Motive tank. May have to buy new hose, but wash it out real good w/ denatured alcohol, fabricate a MC plate and you are off to the races.
If you have to bleed just one caliper, then I prefer the Vac method.
Thread Starter
Navigator
Joined: Sep 2019
Posts: 9
Likes: 0
We have bled the brakes about 4 times after replacing all calipers and rubber brake hoses. Still has a soft pedal. One thing we noticed is after compressing the brake pedal and letting it come back up we could see little bubbles in the mc when the brake pedal was coming back up, does that indicate a leak in the mc?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Lets get back to the beginning.
Was the MC replaced before you started this post?
Was the MC ever allowed to run dry?
Was the MC bench-bled?
Like stingr said. Shouldn't be ANY bubbles in the MC. Even if you correct the MC issue, a fifth complete bleeding is in order.
Was the MC replaced before you started this post?
Was the MC ever allowed to run dry?
Was the MC bench-bled?
Like stingr said. Shouldn't be ANY bubbles in the MC. Even if you correct the MC issue, a fifth complete bleeding is in order.
Last edited by HeadsU.P.; Sep 23, 2019 at 12:34 PM.
Team Owner
Joined: May 2001
Posts: 87,380
Likes: 1,593
From: Western NY
Lets get back to the beginning.
Was the MC replaced before you started this post?
Was the MC ever allowed to run dry?
Was the MC bench-bled?
Like stingr said. Shouldn't be ANY bubbles in the MC. Even if you correct the MC issue, a fifth complete bleeding is in order.be
Was the MC replaced before you started this post?
Was the MC ever allowed to run dry?
Was the MC bench-bled?
Like stingr said. Shouldn't be ANY bubbles in the MC. Even if you correct the MC issue, a fifth complete bleeding is in order.be
Thread Starter
Navigator
Joined: Sep 2019
Posts: 9
Likes: 0
The mc was not replaced, I never ran it dry while bleeding brakes. Always made sure to keep topping off the brake fluid. The mc did not get bench bled
Le Mans Master
Joined: Mar 2004
Posts: 7,502
Likes: 1,510
From: Little Rock AR
I would bench bleed it first to make sure you stop chasing that issue. Then re-bleed the 4 rear screws and 2 front screws again. Need to push out the rear and front bubble formed when you reattach the master. Got to start over from scratch.
Drifting
Joined: Aug 2013
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From: perth Aus w.a
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You can remove the air in the master cylinder by jacking the rear of your car up so the rear of the master cylinder is higher than the front and slowly press the brake pedal a little and you can see the air come out the little holes in the bottom of the master cylinder ,don't press to hard or you will get brake fluid every where as it will shoot out of the small holes ,once no air coming out gravity bleed brakes as normal and you should have a hard pedal
