Thread: give me a brake!!!

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Ok heres the deal. 51 merc with a 78 camaro front sub and a 85 mercury rear. I have a under floor master and booster set up. I have the 2 lb residual to the front and 10 lb residual value to the rear. I have new rear wheel cyl and new front calipers. All new brake lines and fittings. No leaks anywhere. I have bled and bled . I have checked out the master by pluging the outlets and the piston will not move. It is air tight and working right. As soon as i hook everything up the pedal will not pump up. And if you crank it with the vac to the booster the pedal goes to the floor with ease. No brakes at all?

Anybody have any thoughts?

Did you bench bleed the new master cylinder before installation , if its new ?
Are the valves installed correctly ,meaning is the flow the right way?
You could try the vaccume pump type beeding ,if pedal pressure for bleeding is a issue.

Yes it has been bench bled and the values are right. also the bleder screws are at the top to bled all the air out. I pluged the front outlet on the master and the brakes worked alot better. as soon as I hook the front line back up no brakes.

Try to hook the front brakes to the back hole in the master and bleed them ,then re attach to front,if possible?
Bad calipers ?
Bad master cylinder ?
Could be tons of air trapped still,did any fluid at all come out the front?

Hooking the front to the working master cylinder fitting would rule out calipers..................seems awful unlikely that both calipers would be bad or they would not be able to be bled...........,my bet is on the master cyclinder not working correctly.
Swaping the connections would rule the front calipers and determine if the one port was bad on the master cyclinder.
Could be air in the master cylinder still too,might loosen the front fitting and see if fluid is being moved at the cylinder?
I know the motto is bleed ,bleed and bleed some more ,when it comes to brakes.

How tight are the rear shoes adjusted up, and how much clearance do you have in the front rotors to pads? I would crank the rear shoes maybe a little tighter than you intend on finally running them, and start bleeding at the furthest corner.

It sounds to me like you have something going on in the front, since it did improve when you blocked those off.

Don

Yes I have adj the rear shoes real tight and the front pads are new. Although the master checked out ok I may try another one.

So I have pluged the outlets in the master cyl and it has a firm pedal. I then left the plug in the front line and hooked up the rear brake line and had a firm pedal. As soon as I hooked up the front line I had no pedal. I then clamped off the rubber brake line at each front caliper. I had a firm pedal but when I unclamp no pedal. I have replaced the calipers 2 times and vac bled and foot pump bled and still no pedal. This is a 78 camaro sub frame with 78 brakes. Chevy changed calipers around 80 to what they call a slow drag cal. This cal will not work with a reg master cyl. Anybody know how to check on what cal this could be. I am running out options?

Same here... It has to be in the calipers. If you have a pedal with both rubber hoses clamped at the caliper then thats all thats left. But 4 bad calipers is hard to believe.

Just a thought reading your post. If I understand, you have the 2 lb residual going to the disk brakes? If so I would put the 2 lb to the drums and 10 lb to the disc. The other thing, if you watch the master cylinder reservoir when you release the brake pedal does is seem like an excessive amount of fluid is returning? Some should return but not a huge amount?
Ken

I just checked back on Master power brakes web site and it shows the 2 lb to the disc and 10 lb to the drums just like I have it. I will have to check the master cyl level and see whats going on there when I release the brakes..

If you have GM Metric calipers it looks like the bleeders are at the top....but they are not, they are just a little bit below the top. I had the same problem, bled...bled...bled...no pedal. Changed the angle of the caliper re-bled and I had a pedal.

Take your calipers off and set them on the floor,now they will definitely bleed all air out,because it sounds like you have been chasing bubbles back and forth. Hank

I went thru 3 bottles of brake fluid ,getting all the air out of mine...........

I have already set the calipers on the floor and bled them and I have been thru 2 big bottles of fluid. I just got back with a new master and in hopes that the one that came with the setup is the wrong one. By that I'm not sure the bore size and even if its for front disc. When i bought it from mp I ask for drum rear disc front . I know disc front needs 1 1/8 bore and from what I have read the disc side of the master has a larger reservoir. The one that came with it , both are the same size. It could be for a durm durm setup. Not enought to push the disc pistons. Yes I am reaching but whats left.

Do you have the right calipers for the size of rotors that you have? If you have a big car caliper on a camaro size rotor your brakes will not work because the caliper is extended to far out. The same thing can happen if your rotors are turned to thin. I know people will say it doesn't matter because the caliper is full of fluid but, I have run into this problem before on a racecar that had calipers that were from an Impala and I had camaro rotors and on a honda civic because the rotors were turned to thin. I went through a gallon of brake fluid and even took the racecar and had the brakes pressure bled and still no brakes. I took the car home and looked at the calipers and saw that they were already extended out about 1/4 inch. I changed to the narrower calipers and had no problems bleeding the brakes after the change.