flathead31coupe
Well-Known Member
Cool thanks...now I don't know why the part were missing..also note the e brake main cable to the handle is missing as well....all previous owner said was brakes were locking up...he owned for a couple of years
73 duster front brakes locking up when coming to a stop.
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flathead31coupe
Well-Known Member
So after looking at diagrams for the master cell or to the proportioning valve. It looks like the rear master cylinder port , which is the front brakes go to the top of the proportioning valve , is that correct
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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NO! Oh wait, I read your post wrong; So by your description, it is plumbed correctly.
The top of the Combination Valve is for the front brakes; it's just a splitter. Fluid comes in on the end and splits to the left and right calipers. .
The bottom contains the Proportioning valve, and has a single outlet routed to the rear brakes. The P-valve does two things, it delays the brake pressure thu itself, to allow the front brakes to get energized first. and then, it reduces the line pressure to the rear, to prevent them from doing any real work. By design, they are limited to doing about 15% of the work ........................
However
do not confuse the lines going from M/C to the C-valve!
On the M/C the frontmost line is for the rear brakes. From the factory, these two lines have different fittings which makes it impossible to reverse them.
Also
aftermarket or replacement M/Cs often have "residual valves/aka hold-off valves" installed into the ports. That's fine for the port that feeds the rear brakes, but NOT FINE in the front brake system. If yours has one in the rearmost port that feeds the front brakes, it has to be defeated, else the pads will drag on the discs. Don't bother looking for it yet, as you will know right away when the front brakes start working by the fact that the brakes will not release properly.
The test for front brake operation is easy;
just get the front wheels off the ground, then jam a stick between the applied brake pedal and some anchor like the seat or the steering wheel, or just get a helper to stand on the pedal. Then go try to turn the wheels. Obviously, if they are not locked up, then they are not working.
The why of it gets a lil more detailed.
BTW-1
AFAIK, on a Mopar, the guts of a drum/drum M/C and the guts of a Disc/drum system are the same.
The differences are purely between;
the sizes of the reservoirs and
the installation of the residual valves, and
the pushrod retainer, if so equipped.
In other words, any M/C that bolts on to your car, can be made to work, relatively easily.
BTW-2
If the rear brakes on a disc/drum system are bled first, it will make it nearly impossible to bleed the fronts. This is because of the way the M/C is designed.
Once the chamber between the Power-pistons is full of fluid, the frontmost piston is coupled to the brake pedal.
Whereas the rearmost Power-piston (for the front brakes) is designed to slide past the exit port, before sending fluid out to the calipers. So if the front brakelines are empty, whatever fluid moves into the line during the bleeding operation, when the rear lines are already full and sealed, tends to just shuttle back and forth, and never actually transmits any hydraulic pressure. Thus the front brakes cannot work.
There are only two ways around this.
1) The rear line has to be opened to allow the brake pedal to travel fully to bottom the Power-pistons or
2) the rear drums have to be removed to allow the M/Cs some extended travel. If you do this tho, then you gotta not pump the pistons out of the W/Cs making a mess. After every pump, or maybe every second pump, you gotta allow the return springs to park the shoes.
The easiest by far is to unscrew the rear brakeline from the M/C and reinstall the "bench-bleeder", until after the front brakes are bled....... and known to be working.
Please note, once the two systems are both bled and functioning as designed, the discs require very little fluid movement to accomplish braking, and the sliding business that I earlier mentioned, is no longer an issue. As the front system is becoming energized, the fluid in the rear has already pushed the shoes out into contact with the drums, and so braking is ready to begin. After the pedal releases, the return springs in the rear, return the shoes to their parking spots ready for the next application. Simultaneously, "seal-retraction" and disc-runout" have knocked the pads off the rotors, and they too are ready for the next application.
If the rear self adjusting system is defeated, then as the adjustment deteriorates, rear braking becomes less and less effective, until one day, not enough fluid ever comes out to actually push the shoes out to the drums, and that end of the brakes just stops working. This does NOT affect the front brake operation except that the pedal-travel may eventually be a lil longer.
What I'm saying is that, if the guy prior to you bled the rear brakes first, as is usually done on an all-drum system, this could prevent your front system from functioning. However, this should be evidenced by an extended pedal-travel, which you did not mention. The pedal will still be hard after the sliding system has been superseded by the extended pedal-travel.
This is a part of the dual-braking system design, which still gives you rear brakes after the front system has failed, and is normal, in the "failed mode". You just have to be aware of this idiosyncrasy during bleeding.
The top of the Combination Valve is for the front brakes; it's just a splitter. Fluid comes in on the end and splits to the left and right calipers. .
The bottom contains the Proportioning valve, and has a single outlet routed to the rear brakes. The P-valve does two things, it delays the brake pressure thu itself, to allow the front brakes to get energized first. and then, it reduces the line pressure to the rear, to prevent them from doing any real work. By design, they are limited to doing about 15% of the work ........................
However
do not confuse the lines going from M/C to the C-valve!
On the M/C the frontmost line is for the rear brakes. From the factory, these two lines have different fittings which makes it impossible to reverse them.
Also
aftermarket or replacement M/Cs often have "residual valves/aka hold-off valves" installed into the ports. That's fine for the port that feeds the rear brakes, but NOT FINE in the front brake system. If yours has one in the rearmost port that feeds the front brakes, it has to be defeated, else the pads will drag on the discs. Don't bother looking for it yet, as you will know right away when the front brakes start working by the fact that the brakes will not release properly.
The test for front brake operation is easy;
just get the front wheels off the ground, then jam a stick between the applied brake pedal and some anchor like the seat or the steering wheel, or just get a helper to stand on the pedal. Then go try to turn the wheels. Obviously, if they are not locked up, then they are not working.
The why of it gets a lil more detailed.
BTW-1
AFAIK, on a Mopar, the guts of a drum/drum M/C and the guts of a Disc/drum system are the same.
The differences are purely between;
the sizes of the reservoirs and
the installation of the residual valves, and
the pushrod retainer, if so equipped.
In other words, any M/C that bolts on to your car, can be made to work, relatively easily.
BTW-2
If the rear brakes on a disc/drum system are bled first, it will make it nearly impossible to bleed the fronts. This is because of the way the M/C is designed.
Once the chamber between the Power-pistons is full of fluid, the frontmost piston is coupled to the brake pedal.
Whereas the rearmost Power-piston (for the front brakes) is designed to slide past the exit port, before sending fluid out to the calipers. So if the front brakelines are empty, whatever fluid moves into the line during the bleeding operation, when the rear lines are already full and sealed, tends to just shuttle back and forth, and never actually transmits any hydraulic pressure. Thus the front brakes cannot work.
There are only two ways around this.
1) The rear line has to be opened to allow the brake pedal to travel fully to bottom the Power-pistons or
2) the rear drums have to be removed to allow the M/Cs some extended travel. If you do this tho, then you gotta not pump the pistons out of the W/Cs making a mess. After every pump, or maybe every second pump, you gotta allow the return springs to park the shoes.
The easiest by far is to unscrew the rear brakeline from the M/C and reinstall the "bench-bleeder", until after the front brakes are bled....... and known to be working.
Please note, once the two systems are both bled and functioning as designed, the discs require very little fluid movement to accomplish braking, and the sliding business that I earlier mentioned, is no longer an issue. As the front system is becoming energized, the fluid in the rear has already pushed the shoes out into contact with the drums, and so braking is ready to begin. After the pedal releases, the return springs in the rear, return the shoes to their parking spots ready for the next application. Simultaneously, "seal-retraction" and disc-runout" have knocked the pads off the rotors, and they too are ready for the next application.
If the rear self adjusting system is defeated, then as the adjustment deteriorates, rear braking becomes less and less effective, until one day, not enough fluid ever comes out to actually push the shoes out to the drums, and that end of the brakes just stops working. This does NOT affect the front brake operation except that the pedal-travel may eventually be a lil longer.
What I'm saying is that, if the guy prior to you bled the rear brakes first, as is usually done on an all-drum system, this could prevent your front system from functioning. However, this should be evidenced by an extended pedal-travel, which you did not mention. The pedal will still be hard after the sliding system has been superseded by the extended pedal-travel.
This is a part of the dual-braking system design, which still gives you rear brakes after the front system has failed, and is normal, in the "failed mode". You just have to be aware of this idiosyncrasy during bleeding.
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Inertia
Well-Known Member
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Inertia
Well-Known Member
Sooo funny,
I had a discussion here a coupla years ago with someone, - pretty sure Indiana or NE about the legal need for an emergency brake, he said he wasn't gonna install it.
Wonder if that is the car .
Removing parking brake street/strip car
The " Park" brake doesn't hold in reverse. How many times you back outta a driveway or parking space, - put it in "Drive", - and go no-where while the emergency is applied. GM addressed this in the early 80's by putting one emergency cable through the rear of the backing plate, to make that...
www.forabodiesonly.com
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remytherat
Well-Known Member
Post a pic of it. Easy to tell the difference between the drum/drum and drum/disc.
And, yes verify that it is plumped correctly, namely that the line for the rear comes out at the bottom rear port.
flathead31coupe
Well-Known Member
So in this pic , the top break line that goes to the rear of the master cylinder for the front brakes , correct or no
A picture is worth 1,000 words. Where is the picture of your setup?
flathead31coupe
Well-Known Member
I will get a picture this evening
Inertia
Well-Known Member
Yes.
If the master cyl has the largest reservoir closest to the firewll, that is the front disc brake reservoir goes to top center fitting on pic I posted.
Small reservoir goes to bottom of pic to single fitting, then single line out other side to rear brakes.
I say this cuz some masters have large front reserve for disc brakes, and are being sold with boosters for universal fit .
Cheers
flathead31coupe
Well-Known Member
Before my test drive this evening. I checked to make sure that the brake lines were in the proper orientation with the proportioning valve. And they were correct period after a drive around for a bit. For whatever reason, putting all those pieces in the back. Seem to fix the problem breaks. Do not drag and I can stop as normal. Period I also jacked the front end up and spun the front wheels and apply to a little pressure. And they do stop, so the front brakes are working as well. Not sure what happened after reading everyone's input, but putting all those pieces on the rear end for the emergency break.
Assembly And that cross bar between the two shoes seem to have done the trick thanks everyone
Assembly And that cross bar between the two shoes seem to have done the trick thanks everyone
flathead31coupe
Well-Known Member
They were locking up as soon as I used the brakes to stop
All it takes is ONE part to be broken or missing and allow the shoes to contact the drums a little crooked or out of place and they WILL lock up. As you have confirmed. Just like @Jadaharabi first said. He has a tons of experience on these things and there's no substitute for it. People who think they can diagnose the world from their computer, slide rules, formulas and calculators are usually wrong. Glad you got it fixed. Brakes are nothing to mess around with. Can we see some pictures of the car?
One thing I noticed was not mentioned on the front brakes locking up was the spindle nut being too tight. If you do not have that slight bit of play in those front wheel bearings the caliper will not back off and will cause the brake pads to drag hard on the rotor and on occasion lock up.
73 Dusters could be very touchy about this.
73 Dusters could be very touchy about this.
I don't know about that.
A guy I knew that once lived in this:
He owned this car:
One time we were heading south to go to the annual Spring Fling in Van Nuys, CA.
He drove his car, I drove this:
We stopped for gas and I saw grease coming out of the front hub on the right side. He looked closer and determined that it was wheel bearing grease that had cooked out.
FAST FORWARD TO THE POINT:
In an embarrassing display of his "Skills", he had torqued his wheel bearing nut to some ungodly number using FT/LBS instead of Inch/LBS !
This was his second set in a row he did this to. He thought the first set were defective so he replaced them, then did the same dumb thing as before.....he ran the nut down to something like 40-50 Ft/LBS ! Where did he get this spec? If anything, the spec would be Inch/LBS.
I never torque wheel bearings. Nobody else besides THIS guy does either. It is a matter of feel.
He didn't mention any issue with braking or steering but in his "defense", he was always dealing with some failure due to his hack automotive skills.
A guy I knew that once lived in this:
He owned this car:
One time we were heading south to go to the annual Spring Fling in Van Nuys, CA.
He drove his car, I drove this:
We stopped for gas and I saw grease coming out of the front hub on the right side. He looked closer and determined that it was wheel bearing grease that had cooked out.
FAST FORWARD TO THE POINT:
In an embarrassing display of his "Skills", he had torqued his wheel bearing nut to some ungodly number using FT/LBS instead of Inch/LBS !
This was his second set in a row he did this to. He thought the first set were defective so he replaced them, then did the same dumb thing as before.....he ran the nut down to something like 40-50 Ft/LBS ! Where did he get this spec? If anything, the spec would be Inch/LBS.
I never torque wheel bearings. Nobody else besides THIS guy does either. It is a matter of feel.
He didn't mention any issue with braking or steering but in his "defense", he was always dealing with some failure due to his hack automotive skills.
flathead31coupe
Well-Known Member
Sry I mentioned from the beginning saying front brakes i ment the rear brakes not front my mistake...
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flathead31coupe
Well-Known Member
I know that you said rear brakes after saying front brakes. I was just making a statement about my experiences I have had with the 73 duster front brakes locking up.
flathead31coupe
Well-Known Member
Cool ty
One of my favorite colors on those cars! Looks good!
flathead31coupe
Well-Known Member
Ty Now I just have to find the factory for speed shifter that I have posted in the wanted section....
Inertia
Well-Known Member
I'm really glad you got the brakes working correctly.
When you said the emergency stuff was missin I immediately thought un-sprung weight, cuz I build racecars.
We tear out all the struts, levers, cables, and often seriously modify the backing plate to remove every ounce of unnecessary weight, leaving only the wheel cyl/spring mounts, and the pads the shoes ride on.
Being a builder., I automatically think parasitic power loss thru unnecessary weight, sprung and un-sprung weight, friction, rotating mass.
We make the vehicles as light as possible below rule, then add weight where it's needed.
Anyway, when you're more familiar with mechanics, one day you'll look at that strut and lever, smile, and nod your head as you understand.
Here some pix of how we modify backing plates for competition, and the championship rewards after many years of actual building and racing.
Beware keyboard mechanics .
Keep up the good work.
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flathead31coupe
Well-Known Member
Wow thanks I didn't know that.
Inertia
Well-Known Member
Lol, yeah, like me, - some seem to be having memory issues .
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