Need some Brake Guro's Help

[Jared Richey]

1957 Chevrolet.

Converted to MANUAL Disk Brakes. Everything new, master cylinder, hoses, calipers, etc.

1970 Camaro Manual Disk Brake Dual Master Cylinder

Aftermarket Caliper brackets from Double Nickel Chevy to fit the 1973 Monte Carlo Calipers and 70-72 Monte rotors, lot of mixing but thats what is recommended on these tri-fives.

 

Now that everyone knows the background, here is what is happening.

 

We have bled it to death, with a vacuum bleeder and manual bleeding. We still have air in the system, along with the front wheels locking up no apparent reason, but the pedal is spongy and goes all the way to floor still.

HELP!! We've tried everything.

[monte70car]

Hey Jared change the booster to power it will save your legs. Did you buy the brake system as brand new or was it already on the car? Our Nomad has power 4 wheel disc on it and we had no problem bleeding the brakes. My uncle took 70-72 Monte power disc and put it on his 56 Belair and he had no problem bleeding the brakes. It sounds almost like the master cylinder needs to be bleed, and not knowing how long the brake lines been on the car could have a small hole which is letting air into the system.

[Sam (Bones)]

if you are still getting air at all four wheels, put a different master cylinder on it

 

and bench bleed it before installation!!!!!

[Mo's70MCs]

Did you make new steel lines? If so did you use the right flaring tool? I suppose you'd see some brake fluid leaks..my hunch would be mcyl as well. Although stranger things have happen?

[cny first gen 71]

When you say new I assume not reman? correct. Did you bench bleed the master? are the lines coming off the perportioning valve going to the correct wheels? (front to front rear to rear) The fittings or banjo bolts could be sucking some air also. Now I dont want to insult you because I know you know your stuff but I have seen calipers installed on the wrong side of the car with the bleeder valve facing down and air gets trapped in the upper portion of the caliper (just a thought) Have you tried a pressure bleeder sometimes they work better. Make sure the perportioning valve is working. Is there a pressure difference from front to rear? when bleeding. Good luck my friend.

[Nygel]

Pedal going to the floor? I'd say try another master cylinder as well. Bench bleeding always a must! Cheap and easy enough to try.

 

 

Nygel

[Mikstudie]

Jared, perform an isolation test to get you i the right direction..

 

 

Isolation test:

 

Clamp both flex hoses to the front calipers,I use plastic hose clamps made for clamping brake hoses,(vise grips can be used but be careful dont get macho and clamp to tight)

 

 

Clamp rear flex hose(one hose on our cars,two hoses on newer cars)

 

Apply brake pedal,the pedal should be as hard as a rock. If not, Master has external or internal leak.(replace master)

 

 

If pedal is hard have someone remove clamp from rear hose while you apply slight pressure to brake padal. When clamp is removed pedal should drop about 1/8 to 1/4 inch. If pedal drops alot,problem is in rear brakes,leak,air ect....

 

If pedal remains hard replace clamp and repeat with right front wheel and left front wheel in that order, always replace clamp before moving to next wheel.

 

This procedure with get you to the problem area 99% of the time.

_________________________

[420ponies]

DITTO!

Had this happen to my Monte when I got the brakes back on the car.Found the master cylinder was bleeding by.New and bench bled!

[FASTSS454]

Also when bench bleeding never bottom the plunger in the bore, the seals on the piston will be damaged if you do. You made no mention of a porportioning vavle, do you have one in the system and plumbed correctly?

[alex's72fgmc]

first off

did you remember the copper washers for the brake hoses to calipers and the line t at the rear axle?

Double flare brake lines like what was mentioned earlier?

Bench bleed master cylinder with a pair of lines bent back into the resevoir before install and then gravity bleed the system?

did you start bleeding them from the pass side rear then drivers side rear, pass side front to drivers side front?

is it possible you got a power brake m/c instead of a manual brake m/c?

make sure all brake lines are tight?

also the proportioning valve is it the right type for manual brakes as they are different than the ones for power brakes or drum/drum or disc/drum or disc/disc

also with proportioning valve when bleeding the valve can shift to block flow one way or the other this could have happened just press the reset button on it if equiped to where the test light does not light up.

if you did all of this could be the m/c is a bad one.

 

also did you replace the brake rod with one for manual brakes as they are diff lengthes "pushes into the rear of the m/c from brake pedal." this can also result in spongey feel when bleeding brakes as it does not let the piston travel the full distance.