Bad Brake Pedal

[Scrasauge]

ok I have the Granada swap on my 65 and just changed master cylinder and hard lines and flex lines and calipers. My issue is I have good hard stiff pedal when the car is not running but once I start the car the pedal is spongy and goes to the floor. It also is power brakes, I've bleed the brakes over and over again. What can I also look for to get them good again? I'm leaving on Thursday morning for cruisin the coast in Mississippi and need to resolve this issue by Wednesday so I can load up to head out. Can anyone help me with this problem

 

[Moosee1955]

If you have power brakes and pedal is hard and holds but drops to floor, you've got a problem with booster or line from intake feeding it. Power brakes drop a little but don't sink to floor. I would recheck rear wheel cylinders, peel back cups look for wetness, same with front, I'm assuming disc front. Check all brake hoses / metal lines. You might have a high pressure rubber hose that's imploding. Breaking down on inside. Also check valve on booster, make sure it's working/ holding. It's weird that you have hard pedal and then sinks. My guess is something with booster.


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[Scrasauge]

Ok I'll look into that! Also may try pinching soft line going to rear brakes and see if it's in the back brakes that is causing the issue! Also was thinking if rear brake shoes were out of adjustment would that also create one of the issues I'm having?

 

[Moosee1955]

If your shoes are out of adjustment your pedal would be low with the key off. If your pedal is hard and you don't move more than 3 inches or so before engaging, your shoes are good. Do you hear air sound around booster? I had one go bad on a customers 280 z years back. His pedal stayed hard but their was no assist, and you had to mash hard on pedal to stop. Theirs a diaphragm inside booster that fails. Pull rear drums, have someone push pedal, see if shoes move outward. Check both sides, do the same with front discs. If you've got a pressure/ movement problem, you'll know it. With key off, you said pedal is hard and holds? Bad master cylinder will go to floor, wheel cylinder or caliper will pump up and try to hold!


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[The Shemdogg]

adjust the pushrod on the back of the booster towards the master cyl. Just a few turns, reassemble and check the brakes

shemmy

 

[tos]

. Pull rear drums, have someone push pedal, see if shoes move outward. Check both sides, do the same with front discs. !

I would suggest first turning the wheel by hand and having someone press the brakes. If then you find the need to do this with the drum removed then have the other person very slowly press on the brakes or you'll end up with a face full of brake fluid. Those cylinders don't have retaining clips for the piston and can easily blow apart without the drum to restrict the travel of the shoes.
Adjust your rear shoes while turning the wheel and stop when you feel a little drag while turning. This will put your shoes where they need to be and will have little travel to engage when stepping on the brakes.
When you bleed the brakes start at the farthest cylinder from the master cyl IE the right rear. Then left rear, right front and left front. Do it the old fastioned way but don't pump up just break the bleeder loose and have someone push the pedal to the floor and hold it, then tighten the bleeder then release the pedal. Of course do this till you get a nice bubble free stream and repeat for all cylinders/calipers.
If you can get a hold of a pressure bleeder, even better.


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[Scrasauge]

Thanks for the advice Shemdogg, after beating myself up over the brakes, it was in the long run the pushrod was out of adjustment compared to the old master that I had changed out. now the brakes work great on the car and no more pulling to one side or having to pump them once or twice before trying to stop. feels way safer in the car to take my wife for a ride, now to figure out how to get car seats in it to take the kids

 

[The Shemdogg]

Same thing happened to me during my granada brake swap. I figured the booster pushrod was already in the right postion so I didnt move mine and went crazy checking everything else. Finally I found that pushrod issue and I got good brakes but the bump steer friggin sucks. Car is kinda scary to drive but brakes awesome lol

shem

 

[Moosee1955]

Glad you got it figured out.


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