Complete brake system on 69 cougar - now only 1 rear brake works

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  #41  
Old 09-15-08, 07:10 PM
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Billy... you said soft pedal of any kind with the engine off = leaky booster? Was that right? Did you mean MC? Shouldn't the pedal be hard w/o vacuum assist? As you said when pumping the brakes after engine off. That depletes the vac reservoir, right?
 
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  #42  
Old 09-15-08, 09:54 PM
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Originally Posted by nap View Post
softer than they should be and then firm.

Sounds like an adjustment problem or the calipers are not sliding (makes it like the fronts are not adjusting)

actually, you have the function of the brakes backwards. The first activation is the rear brakes. Not to actually provide braking but the rears have much more "freeplay" if you will so that needs to be overcome first so the front and rears will actually provide braking at the same time.



Do you have a couple C clamps handy? I would remove the calipers, leave the pads in place in the caliper or use a piece of flatstock and use the caliper to lock the inner pad against the caliper so the caliper cannot expand. Then try the brake to see how the pedal feels. If no change, I would look to the rears or prop valve.


I have had a prop valve that would not bleed out. For some reason, there was persistant air that simply would not pass.

Not sure how I finally got it out but what I would try is (two people needed); one at the prop valve. Have one person pump up the brakes as high and hard as you can. Then, crack the line going from the prop valve to the back and let it bleed. Do this several times.

I have also done this at the MC when I had persistant air in the MC that I could not get to move.


How far away from University of Notre Dame did you say you were? I do know somebody that will pick up that car for the salvage value
No Nap - you cannot have it for salvage I'm not giving up on the lady in red just yet.

I will try the caliper check as well, since she is still up on stands. However, the problem was there before the install of the new adjustable prop valve so I don't think that is it. Still could be persistent air in the mc or the push rod. Still worth a try however. GI2

Thanks again, you have been a tremendous help.
 
  #43  
Old 09-15-08, 10:01 PM
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Originally Posted by billys68ss View Post
It sounds to me like this post and this problem is getting way too overcomplicated. In 1969 brakes were at their simplest form. With the addition of the vacuum assist booster it made them easier to apply and much safer.
If you have a soft pedal of any kind with the engine off then you have a leaking booster. Without a doubt. If the pedal is hard and gets even harder with every application with the engine off then the booster is fine. It should be hard to the point that you are almost unable to get any action out if it.
Hope this helps ya,
Billy
Thanks Billy, I agree that this is a very very simple system, that is why I'm going crazy. The consensus is that this is a "stupid" problem. It is just one thing that was either wrong from the factory or just a very small thing I am missing. I tend to scratch my head a little on your post however. The pedal is soft on the top and hard toward the bottom with the car off. I agree, the pedal should have almost no play (as it did at the very start of this whole stupid revamp). With the car started it is fairly soft at the top as well, but the rear right brake applies HARD. If the booster were losing vacuum wouldn't I still have even braking pressure? I was under the impression all I would have to do is apply greater force/pressure to the pedal if the booster were bad, the brakes would act like they didn't have power assist.

Could you let me know how to check the booster (other than the soft pedal?). Is there a way to check the vacuum etc?

Thanks
 
  #44  
Old 09-16-08, 05:47 AM
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One thing no one has mentioned yet, a disc/drum master cylinder uses a static check valve in the rear most port(for the rear brakes) to hold a slight amount of pressure in the lines. This is less pressure than the brake springs exert so ther is no brake drag, just enough to keep the wheel cylinder push rods tight to the shoes. Now if this check valve is bad or missing that could account for the mushy pedal at the top of the stroke. If this is not the case I would look at the push rod length on both the booster and the master cylinder. just my 2 cents, hope it helps.
 
  #45  
Old 09-16-08, 08:18 AM
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Double post-----------------------
 
  #46  
Old 09-16-08, 08:22 AM
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Wire twister,

That part is *IN* the MC, right? Poster has new MC. You really think it may be defective or was left out during reman? Poster bench bled MC at install also.

Billy,

You said that without a doubt a soft pedal at any time, with engine off, is leaky booster without a doubt? This would NOT be the case with air in the line?
 
  #47  
Old 09-16-08, 04:12 PM
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lys68ss;1430532]
If you have a soft pedal of any kind with the engine off then you have a leaking booster. Without a doubt.
wrong. there are only several things that can go bad in a booster and if any of them except one does go bad, you will have a hard pedal. If you disagree, please axplain how a booster works and explain how a bad part would cause a soft/mushy pedal.

the one part that will not cause a hard pedal if it goes bad is the check valve. What that will cause, if bad, is a lack of the residual assist after the car is turned off.





If the pedal is hard and gets even harder with every application with the engine off then the booster is fine.
the problem is she cannot get a solid pedal to start with. A bad booster is not going to cause this problem.
 
  #48  
Old 09-16-08, 04:45 PM
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ecman51,
merely advancing a theory, havent you ever gotten a defective part from the part store?
 
  #49  
Old 09-16-08, 05:40 PM
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Just confirming that you think it is a possibility of a bad part. Oddly though, remember that she said in the very beginning, before she fiddled with the front brakes, that she did have a hard pedal then? Does that alter any theory?

Have I ever gotten a bad part? No. Just my dad. I have gotten the WRONG part though. That is quite disgusting also, especially if you had to ride to the parts store on a bike.
 
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