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Discussion Starter #1
Trying to get to first drive and I am now down to brakes. Right now car is on jack stands in the rear with an open diff, stock converter in the trans. When I put the car in gear at idle of course the passenger side wheel turns. I cannot get the wheels to stop with strong effort on the brake pedal whether it is in drive or reverse.
Here are some details:
  1. The brake pedal feels firm
  2. When the car is not running, I get enough rear braking that I cannot turn the wheel by hand.
  3. I have bled the brakes over and over using both gravity and vacuum methods (including bench bleed he master way back when)
  4. Right now the proportioning valve is all the way open (CCW).
  5. I get 1.75" of travel on the brake pedal before it becomes firm and it does not move much past that. I still have lots of travel before hitting the firewall
  6. When I press the brake pedal with the cover off the MC, I get fluid squirting out the smaller rear brake reservoir (can squirt 6" at times) If I keep pressing the pedal continuously the squirting goes away after 3-4 pumps. From my research some say normal, others say not normal
  7. When I look into the MC and watch the piston move it seems like it only moves 1/8" or less (maybe only 1/16"). I really have no idea how far it needs to move but I expected it to be further. The piston barely covers the hole.
Maybe I need to adjust my MC push rod, but the brake pedals seems to be in a good spot with a little play when not depressed which is how I would think it should be. But the fact that the pedal not on the firewall leans I should still have plenty of opportunity to travel more.

Any thoughts? I don't have a basis to know how it should feel.
 

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Here is a thought. When your front brakes clamp down, the pressure in that line will stop the master cylinder piston from moving any further. Perhaps your rear brakes shoes are not adjusted close enough to the drums yet in order to fully clamp down from the volume of fluid being pushed into the rear lines. Normally, if you drive in reverse and apply the brakes, the self adjuster will ratchet the shoes closer and closer. With it on stands, you'll need to either adjust the shoes manually or take the car down and try reversing and braking to see if they tighten up.

Opinions?
 

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Are the rear shoes installed properly (shorter shoe toward front)? Are the wheel cylinder pistons moving freely? Are the wear pads on the backing plate (3 for each shoe) smooth and not grooved? Are the shoes clean and not contaminated with fluids? Are the brake drums within the maximum diameter allowed? Are the shoes properly adjusted (light drag)? Are there any obstructions in the rear brake lines, especially the rear flexible hose? Lastly, for the rears and something not commonly done anymore, is the radius of the brake shoe(s) properly matched to the radius of the drum (arcing)?

Are the front calipers installed properly (free if floating)? Are the pistons free in their bores? Are the dust boots properly installed? Are the brake pads free to slide? Are the front brake hoses in good condition and unobstructed?

Are the front and rear brake lining materials of a quality material and suitable for your type of driving?
 

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Discussion Starter #6
Wow! great replies, and I have a lot of things to check. To be more clear, everything is new on this car front and rear for braking including all hard lines and hoses. Front is the CSRP disc kit. I never drove the car before full tear down.

Rufus68, that is a very interesting point about the fronts. I had not thought of that, though I do think my rears are adjusted properly with a light amount of drag.

Woodchuck, that is quite a list but I appreciate it greatly and will check each and every point.
 

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The brakes were shot when I bought my 68, so being a 16 yo I immediately tore them apart and had NO idea how they went back together. My dad and my uncle just laughed and laughed. My uncle loaned me an old service manual so I could put them back together. I had a similar issue as yours and My dad asked if I had light drag, I told him I could hear the shoes dragging, come to find out it wasn't the shoes dragging on the drum but the drum slightly rubbing on the backing plate. Now I run the shoes out until I can FEEL the drag then back them off to a good spot. Just thought I'd share an experience that I will never forget and maybe it'll help someone.
 

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Not sure if this applies but my 68 with 4 drums brakes is very hard to stop the rear wheels when up in the air spinning in drive. Foot off gas. Sometimes felt like even a high idle can overpower them. But on the ground it’s fine. Stops great. If all the mechanicals check out like Woodchuck and others outlined you may want to bolt together adjust up and try sitting, or inching stops. Be ready on the e-brake pull and use that to benchmark and test both in the air or on the ground. It might be a proportioning valve thing that requires real weight of the car on the ground.
 

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Discussion Starter #9
Not sure if this applies but my 68 with 4 drums brakes is very hard to stop the rear wheels when up in the air spinning in drive. Foot off gas. Sometimes felt like even a high idle can overpower them. But on the ground it’s fine. Stops great. If all the mechanicals check out like Woodchuck and others outlined you may want to bolt together adjust up and try sitting, or inching stops. Be ready on the e-brake pull and use that to benchmark and test both in the air or on the ground. It might be a proportioning valve thing that requires real weight of the car on the ground.
Interesting that you saw something similar. I have been wondering if there is something wrong in the way I installed the torque converter or some issue within it. It seems like it should be "easy" to stop the rear wheels at idle with the brake.
 

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Discussion Starter #10
My responses in bold italics below. Also some pics (pics are from before I adjusted and had installed the pkg brake)


Are the rear shoes installed properly (shorter shoe toward front)? Yes

Are the wheel cylinder pistons moving freely? Yes

Are the wear pads on the backing plate (3 for each shoe) smooth and not grooved? Had to go way back to old photos for this one. All the wear pads are smooth.

Are the shoes clean and not contaminated with fluids? Yes

Are the brake drums within the maximum diameter allowed? Drums are new. I measure right at 10" ID with tape measure with 10.09" outer spec.

Are the shoes properly adjusted (light drag)? Yes.

Are there any obstructions in the rear brake lines, especially the rear flexible hose? Not sure how to check this. I do get pretty good flow of brake fluid at each bleed port under gravity alone. That and the fact that everything is new makes me think I am OK here.

Lastly, for the rears and something not commonly done anymore, is the radius of the brake shoe(s) properly matched to the radius of the drum (arcing)? I just used a contour gauge and they are the proper radius

Here is something new. My brake shoes are 2" width and I was just reading they should be 1.75" Not sure if that could be the problem but it seems like everything fits up OK. I did not buy the rear drum parts, my machinist gave them to me (but all new), so I did not second guess the sizing.


Have not checked the fronts yet but it all went together per instructions.
zzzdriver rear.JPG

Driver
737286

Passenger
 

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If it were me, just out of curiosity I would adjust each side of the rear brakes all the way to a heavy drag so heavy it is difficult to rotate the wheel. With each side adjusted like this I would see if the brake pedal stops the rears. If it does, then what you thought was a light drag was not enough.
 

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You've probably corrected it, but the self-adjuster cable on the passenger side is routed incorrectly (under the guide).

Sounds like you've covered all the bases... the only things remaining are your proportioning valve and the master cylinder. Are you sure that the master cylinder pushrod is short enough that it's allowing the piston to return all the way to the stop? Only other thing that I can think of off the top of my head other than wrong M/C bore size or pedal ratio.....


My responses in bold italics below. Also some pics (pics are from before I adjusted and had installed the pkg brake)

View attachment 737286
Passenger
 

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I just want to point out something. Where else can you get such detailed technical advice? BIG shout out to all who have provided help to Tallguy! This is why this forum is my first go to when I am struggling with something on my car.
 

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Interesting that you saw something similar. I have been wondering if there is something wrong in the way I installed the torque converter or some issue within it. It seems like it should be "easy" to stop the rear wheels at idle with the brake.
Not a torque converter issue. Especially if yours is stock. I had to replace mine twice. The one that came with the rebuilt C4 at purchase time was either bad or incorrect. It worked but shook the bell housing like an out of balance washing machine when revved up. Got a new rebuilt stock type from a place someone here sent me to but I've had this with the brakes before and ever since. Like you my first 'drive' was suspended in the air (on a 2-post lift) I can stop them in the air now that they have been used, it just does it weirdly and disproportionately because of the one wheel spinning (only at idle). The brakes also have this offset thing (forget the correct name think it's called active something....) where one shoe has to catch to engage the other. Might not be catching on both shoes when done in the air. At the very least your e-brake should work. The adjustment nut is below the pass side floor board and you can see it connected to the cable. I've just resorted to shutting off the engine or putting in neutral when I do spin tests at high rpm on jackstands.

I'm not sure, maybe ask one of the other guys, but I think you can push pedal lightly with the drums off and see if the pistons push out. If I'm not mistaken the springs should stop pistons from popping out and return all to place. But double check that before doing it. I've never actually tried. That would definitely be a no-no for disc brake caliper that isn't seated to it's rotor.
 

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Discussion Starter #15
Not a torque converter issue. Especially if yours is stock. I had to replace mine twice. The one that came with the rebuilt C4 at purchase time was either bad or incorrect. It worked but shook the bell housing like an out of balance washing machine when revved up. Got a new rebuilt stock type from a place someone here sent me to but I've had this with the brakes before and ever since. Like you my first 'drive' was suspended in the air (on a 2-post lift) I can stop them in the air now that they have been used, it just does it weirdly and disproportionately because of the one wheel spinning (only at idle). The brakes also have this offset thing (forget the correct name think it's called active something....) where one shoe has to catch to engage the other. Might not be catching on both shoes when done in the air. At the very least your e-brake should work. The adjustment nut is below the pass side floor board and you can see it connected to the cable. I've just resorted to shutting off the engine or putting in neutral when I do spin tests at high rpm on jackstands.

I'm not sure, maybe ask one of the other guys, but I think you can push pedal lightly with the drums off and see if the pistons push out. If I'm not mistaken the springs should stop pistons from popping out and return all to place. But double check that before doing it. I've never actually tried. That would definitely be a no-no for disc brake caliper that isn't seated to it's rotor.
Great info. I think it may be I need to get some miles on the brakes (or at least some stops in a safe place). Looking the the rear pads they are starting to get some wear marking on them and like you mentioned I think once I get them bedded in it will be much better. I did verify that the rear shoes push out with the drums of.

As for the brake offset, I am not sure about that as these should both pull at the same time as they are both plumbed direct to the M/C (through a common hard line). Now if you had one side out of adjustment that would cause an issue too.

I am starting the think that people in my situation probably do not usually start with the rear tires off the ground and just go drive after some garage stop testing. My guess is I would not have noticed this if I did that (as the fronts would have grabbed and stopped me while the rears bedded in). I will get it off the stands and carefully start to gain confidence a few inches at a time.....

E-brake is installed but not adjusted and I will for sure get that dialed in first as a back-up.
 

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I'm not sure, maybe ask one of the other guys, but I think you can push pedal lightly with the drums off and see if the pistons push out. If I'm not mistaken the springs should stop pistons from popping out and return all to place. But double check that before doing it. I've never actually tried. That would definitely be a no-no for disc brake caliper that isn't seated to it's rotor.
Done it. Doesn't tell you much other than the shoes move.

ex-Global West GM
1991-1995
 

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Trying to get to first drive and I am now down to brakes. Right now car is on jack stands in the rear with an open diff, stock converter in the trans. When I put the car in gear at idle of course the passenger side wheel turns. I cannot get the wheels to stop with strong effort on the brake pedal whether it is in drive or reverse.
Here are some details:
  1. The brake pedal feels firm
  2. When the car is not running, I get enough rear braking that I cannot turn the wheel by hand.
  3. I have bled the brakes over and over using both gravity and vacuum methods (including bench bleed he master way back when)
  4. Right now the proportioning valve is all the way open (CCW).
  5. I get 1.75" of travel on the brake pedal before it becomes firm and it does not move much past that. I still have lots of travel before hitting the firewall
  6. When I press the brake pedal with the cover off the MC, I get fluid squirting out the smaller rear brake reservoir (can squirt 6" at times) If I keep pressing the pedal continuously the squirting goes away after 3-4 pumps. From my research some say normal, others say not normal
  7. When I look into the MC and watch the piston move it seems like it only moves 1/8" or less (maybe only 1/16"). I really have no idea how far it needs to move but I expected it to be further. The piston barely covers the hole.
Maybe I need to adjust my MC push rod, but the brake pedals seems to be in a good spot with a little play when not depressed which is how I would think it should be. But the fact that the pedal not on the firewall leans I should still have plenty of opportunity to travel more.

Any thoughts? I don't have a basis to know how it should feel.
Honestly.......and this is directed at nobody in particular...... I don't know how anyone can definitively SOLVE brake
issues without all the tools. A person replaces every single piece in a brake system then is mystified why they can't get
stuff to work.
I'd remove a bleeder and screw in a gauge and determine what I had (or didn't have) for psi. That acid test tells you A LOT.
You can't get 1000 psi at a corner, air in the lines (still) or a master cylinder issue.
Let's say you have plenty of psi at a given corner of the car.... time to look at friction material with a more critical eye.

Your MC piston should move more than 1/8"....... BTW.

ex-Global West GM
1991-1995
 

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Discussion Starter #18
Honestly.......and this is directed at nobody in particular...... I don't know how anyone can definitively SOLVE brake
issues without all the tools. A person replaces every single piece in a brake system then is mystified why they can't get
stuff to work.
I'd remove a bleeder and screw in a gauge and determine what I had (or didn't have) for psi. That acid test tells you A LOT.
You can't get 1000 psi at a corner, air in the lines (still) or a master cylinder issue.
Let's say you have plenty of psi at a given corner of the car.... time to look at friction material with a more critical eye.

Your MC piston should move more than 1/8"....... BTW.

ex-Global West GM
1991-1995

Thanks for the reply. Being an engineer I get the value of the pressure gauge. Never thought of that. I really need to look at the MC piston movement as it sounds like that is not right.
 

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Check where the lines actually go from the distribution block. They should go to the front calipers only. On my wife's 65, the rear line actually went to the passenger caliper. So my plumbing ended up being the rear and driver's caliper on the big reservoir, and the passenger caliper on the little reservoir. Not good. Feb 65 car.
Second, are you solving a problem that doesn't really exist?
Get the wheels on it and adjust like the instructions to see if you really have a problem or not.

From the instructions:

G. Setting the adjustable proportioning valve-APV
1.The mechanical installation must be complete.
2.Turn the APV knob fully counter clockwise.
3. Find a level isolated location with normal road surface. A parking lot would be ideal. Ignore the common advice to use a wet or gravel surface.
4. Perform a series of normal stops, like at a stop sign.
5.Turn the APV’s knob 1-2 turns clockwise in between each stop.

Copyright 2008-2017 CSRP HoldingLLC; All rights reservedhttp://www.discbrakeswap.com

6. Repeat this process until the stop terminates in a little front end dive. This indicates that the front end has commenced braking first.
7.Some fine tuning may be indicated.
 

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Discussion Starter #20
Check where the lines actually go from the distribution block. They should go to the front calipers only. On my wife's 65, the rear line actually went to the passenger caliper. So my plumbing ended up being the rear and driver's caliper on the big reservoir, and the passenger caliper on the little reservoir. Not good. Feb 65 car.
Second, are you solving a problem that doesn't really exist?
Yes, the plumbing is correct. All new and I did it, but still re-verified yesterday.

And yes, maybe I don't have a problem, but still seems like I should be able to stop the wheels while up in the air. I have a hill after I back out of my driveway, so trying to get things dialed before maiden voyage to avoid any oh sh!ts.
 
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