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Really struggling with brakes, drum rear, disc front

9K views 44 replies 17 participants last post by  Tallguy 
#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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#2 ·
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?
 
#3 ·
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?
 
#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.
Auto part Disc brake Rotor Brake Vehicle brake

Driver
737286

Passenger
 
#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.
 
#7 ·
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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#8 ·
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.
 
#9 ·
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.
 
#11 ·
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.
 
#13 ·
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.
 
#17 ·
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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#19 ·
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.
 
#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.
 
#21 · (Edited)
So I think I have an internal problem with the MC. See the pics. When I have the pedal pushed down hard I get 2" of pedal travel. The MC piston starts to move almost immediately when I press the brake. But I get barely any movement on the piston. Maybe I am missing something but just does not seem right. Maybe as has been said already the fronts are clamping too soon but the pedal moves 2" so it just does not add up

EDIT: updated the pics as it was confusing. Rear reservoir is for rear brakes, front reservoir for fronts (versus the physical location on the master where the front is closest reservoir to the steering wheel)
737361

737360

737352
 
#24 ·
The master is the one that came with the CSRP kit. I cannot find a brand or part number. It may come to taking it apart but I am resisting as it was such a pain to get all the connections leak free.

To the OP, not sure if you missed this post #12?..(I've only skimmed the thread) Woodchuck beat me to it about the RH rear drum self adjuster cable.. While this isn't going to cure your bigger problem, it needs to be addressed, as your 'self adjust' while reversing won't work with the cable in that position..

Sent from my SM-G950F using Tapatalk
Yes that was fixed long ago when I put the axles and parking brake stuff in, but thanks.
 
#25 ·
So instead of pulling the master I set up to bleed one of the rear brakes. With the rear line open, now the MC piston moves much further, enough that it actually covers the small recessed port (bypass port I think they call it).

So I did it bleeding only one of the fronts, then the piston for the fronts moved a lot and the rear piston still only moved 1/8" which I think is correct and the purpose of having a dual MC in case of failure on one axle.

So the only way to get more piston travel for the rears (if even needed) is to loosen the pads in the rear.

All that said, I now think the hydraulics are working properly and I either have bad rear pads or they just need to be bedded in.
 
#26 ·
I found some good information on how the dual master cylinder works posted below. I understood this in concept but it makes a lot more sense now. Posting here really just as FYI and to help close the loop in this thread. I am confident my MC is functioning properly. I also learned that the larger hole in each reservoir is not part of sealing the circuit to make pressure. The smaller recessed hole is the port that gets sealed off to make pressure. As I stated in my last post, my issue is bedding or bad rear shoes.

737377


"When you press the brake pedal, it pushes on the primary piston through the linkage to the brake pedal. Pressure builds in the cylinder and lines as the brake pedal is depressed further. The pressure between the primary and secondary piston forces the secondary piston to compress the fluid in its circuit. If the brakes are operating properly, the pressure will be the same in both circuits.

If there is a leak in one of the circuits, that circuit will not be able to maintain pressure.

When the primary circuit leaks, the pressure between the primary and secondary pistons is lost. This causes the primary piston to contact the secondary piston. Now the master cylinder behaves as if it has only one piston. The second circuit will function normally, but the driver will have to press the pedal further to activate it (due to the extra distance needed to make the primary piston contact the secondary piston).

When the secondary circuit leaks, the pressure after the secondary piston is lost. This causes the secondary piston to move forward and contact the end of the housing from the pressure of the primary piston. The primary circuit will function normally, but the driver will have to press the pedal further to activate it (due to the extra distance needed to bottom out the leaking secondary circuit).

In either failure mode, since only two wheels have pressure, the braking power will be severely reduced."
 
#29 ·
Since you've not driven the car after installing the rear brake shoes giving them a chance to bed in, do you think it is possible that perhaps you've been worrying over a problem that isn't even an actual problem? Perhaps you should just make sure you have the brakes properly installed and bled, then drive the car enough to break in the brakes. After this, put back up on the jack stands and check the grip of the rears again.
 
#31 ·
Lots of great feedback and I apologize if I missed it, but what year is your car? You mentioned that the discs up front are a new kit right? Was your car originally a manual or power setup? I only ask because my Father and I installed a pair of front 68 single piston discs onto a 65 fastback. We upgraded to a tandem master cylinder and rebuilt the stock rear drums. We went through a few tandem master cylinders, used two different proportioning valves and even tried a residual pressure valve, but still couldn't get the brakes to feel right. Eventually we discovered that we had a pedal ratio issue because the power 68 discs used a different pedal box than manual brake cars or from the 65-66 pedal box. We swapped the 68 front discs to the stock 65-66 4 piston Kelsey Hays discs and bingo, problem solved. Just thought I would mention it since it seems like you have thoroughly checked a lot of variables. Other than that, have you confirmed that you have a master cylinder with the correct bore size?
 
#33 ·
Car is a 66, original manual drums all around. The CSRP kit was ordered for this set-up. so it "should" be right. Thanks for the reply though.

I had nothing but bad luck with the CSRP kit.

That said, my car did stop.

Are the bleeder screws from your front disk brakes facing up or down?
Bleeders are pointing up. Everything with the CSRP kit seems top notch to me so far. I do not suspect a problem with the kit at this point.
 
#34 ·
New drums too? I went whole hog so there wouldn't be any questions. I agree with your assessment.
While the rear brakes contribute, the lion's share is performed by the fronts with the rears basically just making sure you don't exchange nose for tail in a panic stop. And to be the E-brake. Once you get them bedded and the prop valve adjusted things will be different. Now if the brakes are weird with the prop valve wide open, then you still have an issue. A good test here is in a big parking lot, doing a hard stop with the front wheels slightly off straight. If the rear wants to come around then the rear brakes are gripping too late or not at all. Picture the whole system like a pendulum, and you want to stop straight.
 
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#36 ·
Are the drums themselves new as well? Often times the shoes need to be filed down so they have the same curvature as the drums.
 
#38 ·
Drums are new. At the advice of Woodchuck I did look at that. Se pic. So they are the same shape, BUT, I do see "streaking" on the pads after the braking attempts which I am saying is the pads bedding in. In the pic I did not do a good job lining it up but the curved match. Don't use my contour gauge too much but a few times on the Mustang.
737489
 
#39 ·
Drums use shoes, rotors use pads. Anyway, are you still working on this before driving it? If you have a solid pedal, your front brakes will stop you so no reason not to carefully put some miles on those rear brakes. Remember to reverse and stop to allow the automatic adjusters to do their thing.
 
#42 ·
To bad you didn't live closer, I'd let you borrow my brake pressure testers. I have one kit that you connect into right at the fitting, such as at the master, caliper, wheel cylinder, etc. It gives you the hydraulic pressure at that point. Be curious to see pressure readings at both your wheel cylinders. The other kit is a pressure puck you put in place of the brake pads and the caliper piston pushes against it an gives you a read out on how much pressure the caliper is applying. Very handy tools!
 
#43 ·
Follow up:

While still on jack stands I adjusted the parking brake and was able to stop the wheels from turning in gear. I ran it some more on the stands while using the brake pedal to sort of wear the pads in and was able to get it to where I could stop the wheels with the pedal.

So off the jack stands and did some careful fwd/rev stops in and out of the driveway. Not great but it stops. Around the cul de sac, and did some more deliberate stops/starts and it stops OK. Today had it out around the block and did more stops and seems to be improving as I would expect. Still need to do a full bed in procedure and to set up the proportioning valve but have not ventured out far enough to find a good spot.

One problem is I really don't know how these should feel Have not had "manual" brakes since 1989. All my cars since stop on a dime. The Mustang definitely takes some effort and that is OK, just have to be aware to stop earlier than my daily driver.

So I guess I really did not have a problem, just was very concerning to me at first.
 
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