Brake system issues remain - next steps??

[moparedtn]

Some of you may recall the epic battle I went through a year+ ago to rebuild the entire drum brake setup on Fred, the 1968 GTX.

All "Made in the USA" parts were sourced and everything was replaced, front and rear with new as I found new old stock stuff that fit that criteria, except:
1. Drums - I have quite the collection of 11" drums front and rear, all machined and within tolerance, so I mixed and matched to get the best ones on the car.
2. The left front hub was also replaced due to hogged out lug holes. That was an experience in itself, only possibly solved by a fellow FBBO member who had one that he donated!
3. The original front hard metal lines remain in place after flushing; all other hard and soft lines front and rear are replaced and the original splitter block also remains.
4. The master cylinder was new on the car when I bought it (aftermarket, probably reman)
and remains on it now.
Other than specifically mentioned, everything is new on the system.

My thread on all the project:
https://www.forbbodiesonly.com/mopa...l-now-for-something-totally-different.218808/
Highlights included "converting" the fronts to self-adjusters from 1969 as well...

Now for the continuation of the project because - you guessed it - things still aren't
right. In fact, they've proven to be doggedly, stubbornly (and dangerously) NOT right.
The left front has returned to the one that locks while the others don't; the pedal
refuses to stay "up" after the typical "back it up/hit the brakes" exercises.

I've had the fronts apart a half dozen times a side since then and nothing, nothing,
is out of place; the system has been bled to death as well. Real good, even pressure
at each wheel when bleeding, too. No evidence of clogs or restrictions...

Typical long-winded description of all the above leads me to now - I basically
have a couple questions:
1. Is there any functional difference between the typical aftermarket replacement
master cylinders out there now, as pictured:

...and the "discontinued" original ones, as shown in the FSM:

When it comes to standard, non-power 4 wheel drum brakes, is there any difference
mechanically between these two master cylinders?

2. I'm going to replace the hard lines in the front system, since they're the last original parts of the brakes left.
Sorry to disappoint but no, I won't get into making my own. Reasons...
Two-part question:
a. Lots of sources of repro lines out there. Any of them better than the others?
b. Are the metal lines on drum cars the same as those on same-year front disc cars?
(Yes, in the back of my mind, I'm wanting to hedge my bet here in case I wind up pulling
the trigger on a disc swap in the end.)

Thanks in advance!

 

[Aron Gleason]

I'm interested in knowing what others say. I have to pull up on the brake pedal to release the brakes.

 

[Geoff 2]

If power brakes, the internal spring in the booster returns the brake pedal. Non-PB will require a spring on the pedal assy to return the pedal.

Locking front left brake:
- sediment in the line or hose can cause this.
- drive car for 15 min with gentle brake applications. Feel both front drums for heat. If left side is hotter, could be out of round drum rubbing, wheel cyl sticking.
- make sure brake shoes are correct & same material. Short shoe goes to front, long shoe to rear.

 

[kiwigtx]

Make sure the shoes are oriented the correct way - there is a leading edge, and a trailing edge.

I had 4-wheel drums on my A100.....but have now swapped to front discs. My drums worked great considering what they were, but they were fitted by an expert in the field of braking. I only changed because I was concerned that over time I would eventually get brake fade etc, ad need to make significant repairs anyway. And I have also added a vacuum booster to the discs...so it gives me a great brake effect with the comfort of a softer pedal.

Contaminated shoes will also make an impact on braking capacity as stated above.

 

[moparedtn]

Locking front left brake:
- sediment in the line or hose can cause this.
- drive car for 15 min with gentle brake applications. Feel both front drums for heat. If left side is hotter, could be out of round drum rubbing, wheel cyl sticking.
- make sure brake shoes are correct & same material. Short shoe goes to front, long shoe to rear.

The processes you've described are logical - and have already been performed, endlessly
(see my previous thread, which includes video if I recall correctly).
Shoes are brand new (as in fresh manufactured by Potterfield in California) and drums (I have a handful, as I stated)
and shoes were all tried, rotated, swapped side to side to see if any individual component was the culprit.
Same results, no matter what configuration was tried...
Been through several containers of brake fluid in this process as well. If something is still contaminated in there,
it ain't coming out unless I tear the whole hydro system down....
which leads me back to my original questions.

Make sure the shoes are oriented the correct way - there is a leading edge, and a trailing edge.
I had 4-wheel drums on my A100.....but have now swapped to front discs. My drums worked great considering what they were, but they were fitted by an expert in the field of braking. I only changed because I was concerned that over time I would eventually get brake fade etc, ad need to make significant repairs anyway. And I have also added a vacuum booster to the discs...so it gives me a great brake effect with the comfort of a softer pedal.
Contaminated shoes will also make an impact on braking capacity as stated above.

Yes, well aware of orientation of the shoes. All cars of that certain generation are that way, in fact. Grew up being taught that particular aspect by my dad; of course, the FSM was open and consulted ad nauseum as well.
As stated above (and described in detail in my previous thread), the shoes are fresh manufactured and the compound
is quite aggressive, although not their "race" blend but what they described as HP Street.

Thank you both for taking the time to reply, gentlemen.
Now, returning to my original questions:
Typical long-winded description of all the above leads me to now - I basically
have a couple questions:
1. Is there any functional difference between the typical aftermarket replacement
master cylinders out there now, as pictured:

...and the "discontinued" original ones, as shown in the FSM:

When it comes to standard, non-power 4 wheel drum brakes, is there any difference
mechanically between these two master cylinders?

2. I'm going to replace the hard lines in the front system, since they're the last original parts of the brakes left.
Sorry to disappoint but no, I won't get into making my own. Reasons...
Two-part question:
a. Lots of sources of repro lines out there. Any of them better than the others?
b. Are the metal lines on drum cars the same as those on same-year front disc cars?
(Yes, in the back of my mind, I'm wanting to hedge my bet here in case I wind up pulling
the trigger on a disc swap in the end.)

 

[hangn0ut]

Residual pressure valves? Self adjusters lubed up and working properly and evenly. Parking brakes hanging up somehow. Shoes arced in? Just thinking out loud.

 

[moparedtn]

Residual pressure valves? Self adjusters lubed up and working properly and evenly. Parking brakes hanging up somehow. Shoes arced in? Just thinking out loud.

The residual valves were originally in the master cylinder, yep - but those wouldn't explain side-to-side
issues in the front brakes, since that's all one circuit.
Still, I wonder if residual valves are perhaps an issue with the current master cylinders vs. the originals,
hence my question on those?
Parking brakes - no issues with rear brakes, parking brake works normally (has to, given this is a 4 speed car).
As far as the self-adjusters go, they're all new - and the fronts were added since '68 didn't have those to
begin with ('69 all new hardware used to "convert" the car).
I am tempted to remove all of that and return to the '68 configuration, but that would be just for "what-if"
purposes...
Shoes being swapped side to side to me eliminates any production differences - same exact behavior
was displayed regardless of which shoes were on which side.

 

[bobsgtx]

You have probably tried this but this is where I would go. If the self adjusters are the cable type leave the cables off the front brakes and manually adjust them the same and see what happens. If the same(LF working more then RF) then you have to look at hydraulic system from tee/pressure differential switch to front wheel cylinders. I know they made pressure gauges for checking brake pressure but I never needed one in 45 years of wrench turning. It would be nice to swap front wheel cylinders but I assume they are different and can't be done. As for something stupid and outside the box check the ID of the wheel cylinders. I've seen some strange stuff over the years. Pressure should be equal on both front wheel cylinders. Good luck.

 

[moparedtn]

You have probably tried this but this is where I would go. If the self adjusters are the cable type leave the cables off the front brakes and manually adjust them the same and see what happens. If the same(LF working more then RF) then you have to look at hydraulic system from tee/pressure differential switch to front wheel cylinders. I know they made pressure gauges for checking brake pressure but I never needed one in 45 years of wrench turning. It would be nice to swap front wheel cylinders but I assume they are different and can't be done. As for something stupid and outside the box check the ID of the wheel cylinders. I've seen some strange stuff over the years. Pressure should be equal on both front wheel cylinders. Good luck.

Thanks for replying and you're actually hitting on the line of thought I'm actually on right now!

I kept all the old hardware from the self-adjuster conversion and I had thought of throwing that part of
it back on the fronts - just to see what happens (I don't think the self-adjuster stuff will stay in place with
the release of that cable tension).

Yep to the lines/block being next - even though I get normal streams from the bleeders, I gotta wonder since they're
original to the car. No, the front wheel cylinders don't interchange (bleeder location).
However, you do bring up an interesting point - yes, the wheel cylinders are new and yes, I did research part
numbers when fetching all the stuff for the overhaul, but the brands are all mix-matched amongst components
as I literally bought the last remaining "NIB" USA-made stuff in some cases!
I need to look into that if I'm going to keep drums on the front - and perhaps consider trying other w.c.??
The situation is very much like one side is working harder than the other - like the wheel cylinders have different
specifications??

 

[oldbee]

I’m sure you’re a little exasperated! Have u tried removing drums on the front & gently pushing down the pedal and watch brake operation? Any sticking or such going on?
I’m a little leary of QC anymore.

 

[LowBikeMike]

RE: Wheel Cylinders. I would think bore size would be standard across the application. But, it could be something as simple as piston length or depth the pin that engages the shoe fits into the piston.

 

[ruffcut]

Ed, I've been following along and my 2 cents says either the distribution block
or master cylinder. I'd be surprised if anything else is the culprit!
Wishing you lots of patience and good luck!
ruffcut

 

[moparedtn]

I’m sure you’re a little exasperated! Have u tried removing drums on the front & gently pushing down the pedal and watch brake operation? Any sticking or such going on?
I’m a little leary of QC anymore.

Oh brother, there has been so much testin' and proddin' and swapping of like parts....

RE: Wheel Cylinders. I would think bore size would be standard across the application. But, it could be something as simple as piston length or depth the pin that engages the shoe fits into the piston.

I do know there is a difference between the 10" and 11" wheel cylinders. I don't have any 10" ones to compare to, but I'd bet the difference probably is bore-related? I'd think the "throws" would be the same as far as the cylinder part goes, perhaps any differences being taken up with the forks that hold the shoes from the cylinders?
I have not attempted to swap those "forks" from one side to the other or such, but I do know everything fits and
adjusts the same from side to side; there isn't any indication of "arch" issues apparent on the shoes so far, anyways.
OH, important point I forgot to mention - this "one side grabbing" situation did not exist prior to the overhaul (brakes just sucked all around in general before) and I have not moved those forks from their original wheel location.

Ed, I've been following along and my 2 cents says either the distribution block or master cylinder. I'd be surprised if anything else is the culprit!
Wishing you lots of patience and good luck!
ruffcut

Yessir, that's where my own crusty old thought train is headed also my friend - and thank you for your support!
Ed

 

[moparedtn]

I have a couple questions:
1. Is there any functional difference between the typical aftermarket replacement
master cylinders out there now, as pictured:

...and the "discontinued" original ones, as shown in the FSM:

When it comes to standard, non-power 4 wheel drum brakes, is there any difference
mechanically between these two master cylinders?

2. I'm going to replace the hard lines in the front system, since they're the last original parts of the brakes left.
Sorry to disappoint but no, I won't get into making my own. Reasons...
Two-part question:
a. Lots of sources of repro lines out there. Any of them better than the others?
b. Are the metal lines on drum cars the same as those on same-year front disc cars?
(Yes, in the back of my mind, I'm wanting to hedge my bet here in case I wind up pulling
the trigger on a disc swap in the end.)

 

[Billccm]

On the Dr Diff conversion kit the lines are the same.

 

[hangn0ut]

I have a couple questions:
1. Is there any functional difference between the typical aftermarket replacement
master cylinders out there now, as pictured:
View attachment 1283590

...and the "discontinued" original ones, as shown in the FSM:
View attachment 1283591
When it comes to standard, non-power 4 wheel drum brakes, is there any difference
mechanically between these two master cylinders?

2. I'm going to replace the hard lines in the front system, since they're the last original parts of the brakes left.
Sorry to disappoint but no, I won't get into making my own. Reasons...
Two-part question:
a. Lots of sources of repro lines out there. Any of them better than the others?
b. Are the metal lines on drum cars the same as those on same-year front disc cars?
(Yes, in the back of my mind, I'm wanting to hedge my bet here in case I wind up pulling
the trigger on a disc swap in the end.)

Functionally there is no difference that I know of. And the cylinders pictured will work on a disc brake car. The size of the reservoirs being the difference. Disc need the larger reservoirs as the pads wear.

 

[Geoff 2]

Drum brakes usually had a Residual Line Pressure Valve in the outlet port, behind the brass ferrule. This must be removed for disc brakes, otherwise the discs will stay 'on'.

 

[moparedtn]

Drum brakes usually had a Residual Line Pressure Valve in the outlet port, behind the brass ferrule. This must be removed for disc brakes, otherwise the discs will stay 'on'.

Do they ever mention this in the instructions for the various conversion kits out there I wonder?

 

[69L48Z27]

I was always under the impression that residual valves were needed when the MC was lower or at the same height as wheel cylinder. The MC being higher gives the line some ambient residual pressure. Lack of residual valve or pressure should not cause uneven braking, pulling. The return of the pedal should be all in the MC. If you pull it off the car and bench bleed and it has a strong return then I would check the shoe return springs. You can clear out your hard lines. I wouldn't replace for the sake of replacing. I also think your to the point where you may want borrow or buy a brake pressure gauge and see what your getting on all four corners. In regards to pulling side to side. I’ve always had to adjust that out. Also, make sure the car has a good alignment. Toe and bump steer issues will drag the car around under moderate braking.

 

[moparedtn]

Well, it appears seeking knowledge and opinions on this subject has been an abject failure...
I'll figure all this out the hard way I reckon.