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New Brakes NO stop,


Capt Mark

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Ok here it goes.....

The car has not run for five years, bringing it back to life......

I completely opened and fushed the lines, installed a NEW master, NEw rear wheel cylinders, NEW brakes and hardware all around, bled it out 3 times, there is NO air in the system, no leaks, everything looks like it should.

Could the brake booster be bad? How do I check it? any other ideas?

Thx Capt Mark

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Even if the booster was bad, you would still have brakes-not nearly as good as with the booster, but standing on the pedal would stop the car.

here are some suggestions

1) To check the booster, pull off the hose hoing from it to the intake manifold(take it loose at the manifold.) suck on it-the vacuum should not leak down, if it does, the diafram is broken.

2) Did you take the booster out of the car? If so, there is a pin inside it that holds the linkage that has probably fallen out-it is a pain in the azz to get back in.

3) Did you bleed the master cyl. by its self? Sounds like that is here your air is if you didn't.

Will

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Thanks Will, .....I bled the master out on the bench, I did not pull the booster, the pin is in the correct position and if I pump it 3 times is does stop, I just do not have apedal.....I will check and see booster is bad.

If pumping it three times makes it stop then I'd say you've got more bleeding to do. As Will said, even without the booster the brakes should still work. You can verify this by removing the vacuum hose from the booster. You loose the power assist but you can still brake the car.

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Having had a similar experience, I can say that my problem was reinstalling the calipers with the bleed valve on the bottom. Had spongy brakes and no stopping power until i flipped 'em over and got the last little bits of air out. I guess looking at the service manual during the reinstall would have saved me the trouble.....LOL

Are your calipers on properly?

X

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"1) To check the booster, pull off the hose hoing from it to the intake manifold(take it loose at the manifold.) suck on it-the vacuum should not leak down, if it does, the diafram is broken."

I went out and hooked a vacum up to the boost and got zero, I bled out the system 4 times....I primed all the line with a vac the had some pump and hold the pedal with a hose in the cup method. No air in the system....... BUT the car was not running will this make the difference.......

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You didn't respond to xray's post, so I'll ask the question again. Did you confirm that the calipers are installed on the correct sides of the car like xray mentioned? The calipers can be mounted upside down. The bleed nipples MUST be at the TOP of the calipers or you'll never get all the air out of them

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Carl,

Yes, The nipples are on top......he he he.....too funny.....

I am going to do the booster anyways, that way I will have a complete new brake syatem........Will I have to take OFF the master in order to change the booster? or will I be able to move

out enough to get the bboster out?

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Have you checked the adjustment of the rod between the brake booster and the master cylinder? If there is a big gap between the end of the rod and the piston in the master cylinder some of the brake pedal engagement will be used to take up the gap. Best method is to take detailed measurements to insure there is only a slight gap (.050) between the two after assembly. Be careful not to set the rod too long whereby the piston in the master cylinder has started to move after final assy. I experienced similar problem when installing new master cylinder and new brake booster. Later model boosters/master cylinders used adjusting rods of different length. I wound up using my original rod (as del'd from factory) with the new booster. After setting rod correctly, brakes work great.

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I haven never tried to move it away and pull the booster-sounds like it is worrth a try, but keep an eye on your lines, better to have to bleed again than to replace a crimped or collapsed hard line.

Will

Exactly why I wouldn't even try it. (This is just the kind of thing that bites me on the a$$ everytime I try to save time/effort) Of course I have Speed Bleeders on the car so re- bleeding isn't any trouble at all.

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99.99999% sure the reaction disk fell out. The reaction disk is a small rubber disk inside the booster. It sits right in the middle of the booster, and can fall out when you separate the master and the booster. It should be down in the bottom of the booster. Fish it out and put it back in its place. Everything should be good to go afterwards.

While I haven't had this problem myself I've seen quite a few posts about it over the years, and they all said exactly what you said: "Bled the system 57 times, everything is brand new, still no pedal."

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99.99999% sure the reaction disk fell out. The reaction disk is a small rubber disk inside the booster. It sits right in the middle of the booster, and can fall out when you separate the master and the booster. It should be down in the bottom of the booster. Fish it out and put it back in its place. Everything should be good to go afterwards.

While I haven't had this problem myself I've seen quite a few posts about it over the years, and they all said exactly what you said: "Bled the system 57 times, everything is brand new, still no pedal."

Very good point.

A search should bring up several threads (some with diagrams, etc) on this subject.

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Is brake fluid a rust inhibitor or a cause of rust? I had thought it was an inhibitor but I found so much rust where brake fulid would have leaked.

The problem is that over time water can build up in the brake fluid and that can cause rust.

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Jon,

I checked it out and the reaction disk is in place correct, reconnected everything and still no vacuum assist from the booster, I went ahead and ordered a replacment today. $72

thanks for the tip, I will make sure it is in place when I put in the new one.

Mark

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Are you absolutely sure you got the correct master? I believe the rod may be different from "newer" models. I do know the 71 vs. the 72 model years are different. I ordered one some time ago and was sold the wrong one. Didn't notice until lots of wasted hours trying to get it to work. Also be sure you get the same booster if you get another. Had a problem with that issue also...the attaching pin was different than what I had. Different thread size wouldn't fit properly.

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I got brakes today!!......the booster was bad.....and I changed it with out getting air in the system......I was very carefull and very gentle with the hard lines....I loosened all the hard-line mounting brackets and took the spacer between the master and the booster off…the rest was ez…… Many thanks to everyone that help me out.......

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