New build....brakes not cooperating

I'm just finishing up a '65 Chevy II SS, tube chassis 18 month long build. I'm using all new brake components, including Strange discs all the way around, all new lines, residual valves front and rear, proportioning valve, and line lock, and new Strange master cylinder ( it was bench bled). I must be missing something, as I've bled this entire systerm over and over, and always come up with the same scenario. The first pedal pump goes to the floor, then the pedal is all the way up, and loses no firmness no matter how long you hold it. I've bled manually, and with a power bleeder....the same results. Brakes have always been a problem with me...I hate them. Thanks for any input.

It's probably silly, but the first thing that popped into my head was that the calipers, or a pair of calipers might be swapped side to side, putting the bleeders low on the caliper instead of at the top where the air collects. If you have a pair of bleeders sitting low you'll keep a pocket of air in those two calipers. Just a thought.

Oh good, another way to screw up.:HMMM: Hope I can remember that one. :rolleyes::)


Jack.

Strange 4 piston calipers.....they have bleeders top and bottom, so depending on how you fit them, you have a pair of bleeders for each caliper on top. Of course, you don't touch the bottom ones. Thanks for responding.

The first thing thatpopped into my head was the residual valves weren't holding. They are responsible for keeping the calipers full of fluid.

That first pump re-fills the calipers. Somehow you need to verify that they are holding back at least 2 pounds of fluid & pressure. Do you have any high pressure gauges and fittings? Test the pressure created by the pedal and then watch what it drops to.

Maybe just change the residual valves? Do they go bad? I suppose they could. Thanks.

somebody i know installed them backwards once ........ :(

I called Strange to verify that when I first started having this problem. The OUT goes to the caliper side...is what they said.

I maybe confused, and that is often the case. However, I thought you used residual valves only when the master cylinder was lower than the calibers?

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Originally Posted by 36 sedan

I maybe confused, and that is often the case. However, I thought you used residual valves only when the master cylinder was lower than the calibers?

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Good catch, 36 sedan! 100% right, residual valves are not needed for a '65 Chevy II with firewall mounted master.

well actually---disc brakes aren't adjustable like drum brake shoes to keep peddle high and do use residual valves to maintain a closeness pad to disc no matter where the master cylinder is located
they just use a different pressure value


lots of master cylinders have the residual valves in the master

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Originally Posted by jerry clayton

well actually---disc brakes aren't adjustable like drum brake shoes to keep peddle high and do use residual valves to maintain a closeness pad to disc no matter where the master cylinder is located
they just use a different pressure value. lots of master cylinders have the residual valves in the master

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Well, these guys, for one, disagree - Typical Brake System Configurations They show NO residual valves for a firewall mounted master with discs all around.

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Originally Posted by rspears

Good catch, 36 sedan! 100% right, residual valves are not needed for a '65 Chevy II with firewall mounted master.

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it could if the master volume needs to be bigger most guys like the vett master for that

some sell shims under the brake pad to take up space less pedal travel when using a thinner rotor wilwood and other s do this go back and check the push rod that you not up on the rubber bumper on the stock pedal set up . i had to take bumper off and make the push rod longer

Maybe have an assistant eyeball the calipers during the first pump. Look for pads moving, they should have little discernable movement. It almost sounds as if the pads are popping back away from the discs, similar to shoes not properly adjusted to drums.

https://onedrive.live.com/redir?resi...t=photo%2c.jpg


using there words , but change the words drums to discs, change 10# to 2 #, change shoes to pads------------


In the op post-----the first pedal push takes up slack and 2nd is then hard!!!!!!! the reason the 2 # valves were developed was because the 10# make the pads drag and they still needed something so they came up with a 2 #----------------

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Originally Posted by jerry clayton

https://onedrive.live.com/redir?resi...t=photo%2c.jpg


using there words , but change the words drums to discs, change 10# to 2 #, change shoes to pads------------

In the op post-----the first pedal push takes up slack and 2nd is then hard!!!!!!! the reason the 2 # valves were developed was because the 10# make the pads drag and they still needed something so they came up with a 2 #----------------

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Your link is to a bunch of your pictures....???????????????????

Not sure about that link. It links to the AF museum.

OKKKKKKKKK Sorry---I tried to post that pic of the radial engine in Scooters thread-------


then tried to copy/paste some words right from RS post but changed some words so as to explain that disc brakes should have a 2# valve to maintain pad proximity to disc just like drums need 10# to keep shoes close to drums--------


The use of these valves goes back several years and most likely not a single OEM disc brake car ever had a master under the floor----the use of a master with a big and little reservoir tank was common for drum/disc combo -------


I know it is internet theory that the disc only needs the valve if the master is under the floor but the most important thing is NOT to use a 10# on discs or the brakes will drag creating lots of heat and brake fade---------


The 2 # will barely do anything except keep the pad near the disc (disc runout will creat running clearance) no matter where your master is located-------------

So the bottom line is that no residual valves are needed for a stock OEM installation where the master is on the firewall and all slaves are lower.

No-------bottom line is to use 2# valve for disc brakes----

Sorry...I thought I clarified earlier....the master cylinder is mounted below the calipers. The brakes are Strange discs, all components are new, except the 2# residual valves, which are installed in the front and rear lines. I ordered new residual valves and will get them tomorrow. I just don't have a lot of confidence in that being the problem. Thanks for all the suggestions.

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Originally Posted by lodilobo

Sorry...I thought I clarified earlier....the master cylinder is mounted below the calipers. The brakes are Strange discs, all components are new, except the 2# residual valves, which are installed in the front and rear lines. I ordered new residual valves and will get them tomorrow. I just don't have a lot of confidence in that being the problem. Thanks for all the suggestions.

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when i my built my race GTO i hade a line lock .wilwood disc front and back . i just had a proportion valve that i could adjust brake bias master was mount on the floor as the engine was moved back 5 inchs. i did use residual check valves#2s . the stander master many resell under there name. but is mopar master with a 1 1/16 bore i used this master on all my cars . was told at the time to put residual check valves as close as i could to the master and i did . after many bleeding the master i had good pedal was a pain in the ass. but had more parts in the system and alot them 1/8 npt to female inverted flare as for that guy should be shot for that ideal . it was a uphill battle to get sealed up . if you have a power bleeder un hook the pedal push rod then bleed it then hook up the pedal push rod if pedal feels better need to work on the push rod and check that there is nothing a the way holding pedal travle back. some proportion valves like gm 1971to77 had some residual presure built in for better braking feel. if you feel every thing is right then look at the master sucking air. if you want a cheat some lets say the rotors you have are 375 thick go find a cunk of metal about same in size unbolt the caliper lay on the floor or milk crate still hook up then bleed them that way master not level they will bleed better