1973 Dart brake failiure

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Yes, I have four drums, if that's a disc MC than I have no idea how it got there.

I do plan on replacing or repairing the MC, but I'd like the vehicle to be operable atleast every now and then so I'll probably try to refill it tomorrow and see if it holds at all.

And yeah, when the brakes went away I was driving, luckily only about 15, and luckily on a flat road.

Goes without saying im not looking to temporarily fix this problem, but if I do get a replacement it will take weeks to ship out here.
 

Also, how come the rear brakes don't seem to do anything even with all that fluid in the front reservoir? I get they're kinda supposed to be weaker than the front but it still seems like I can't brake at all
 
SputnikOne said:
Also, how come the rear brakes don't seem to do anything even with all that fluid in the front reservoir? I get they're kinda supposed to be weaker than the front but it still seems like I can't brake at all
Click to expand...
maybe they are stuck
froze wheel cyl can give a solid pedal and no brakes
also, you had the e brake, I've used that in situations before
was actually tought that in drivers ed, properly stoping with the emergency brake
 
Dana67Dart said:
No one not there can say if a temporary fix will last for any amount of time.

I would plan on replacing or rebuilding or haven't the master cylinder rebuilt.

It will not magically fix itself.

When mine leaked under the carpet it removed all the paint it contacted to bare metal.


Luckily I have never had a catastrophic brake failure but I know someone who has.

I'm pretty sure he had to change his shorts and was an hour from home.



For the short term, you could add fresh fluid and bleed your brakes front and rear

Then have someone observed the back of the master cyl where it's leaking. You press on the pedal hard and see if fluid seeps out.

That will tell you if you can squeeze out a week or two.

Monitor the level very carefully.

But you may be taking your and a strangers life in your hands
Click to expand...
"It will not magically fix itself."
I have gotten brakes going on many old trucks by just soaking, cleaning, and re-hydrating seals
these brake systems need movement and fluid to stay alive
most people never need calipers or cylinders
they need carefull cleaning and seals need 48+ hrs to hydrate
that includes new stuff.
 
I wish I could say I has the parking brake, alas that is a whole nother issue, yeah, no breaks right now.
 
By 1973 more cars were equipped with disc brakes so Chrysler started using disc / drum master cylinders on manual four wheel drum cars. It was a gradual process and took a few years to complete the change on all cars.
This was easily accomplished by using residual valves in both front and rear ports.
Also wheel cylinder expanders were being widely used by this time so there really was no need for residual valves.
Some of the aftermarket companies continued making the old style manual drum master cylinders.
In the 1973 parts catalog the all drum manual master cylinder was #3580209.
Here's a photo of the 1973 master.

 
SputnikOne said:
Also, how come the rear brakes don't seem to do anything even with all that fluid in the front reservoir? I get they're kinda supposed to be weaker than the front but it still seems like I can't brake at all
Click to expand...

While the divorced hydraulic system was supposed to allow the front to work if the rear has a leak (or vice-versa) I've found that if one end fails, the other is terribly inadequate at stopping a car.
dr dodge said:
also, you had the e brake, I've used that in situations before
was actually tought that in drivers ed, properly stoping with the emergency brake
Click to expand...

Technically, it is not an "emergency" brake. It is a parking brake meant to hold the car still after it has been stopped. For that purpose, they work as intended. In an "emergency", they are not as effective as your regular rear brakes since they only engage the rear brake shoe, not both front and rear shoes.
The fix here?
Replace the master cylinder with the appropriate unit.
 
Post #7. Unless you just filled that front chamber, where did ALL that fluid come from? Internal leakage inside the m/c. Fluid being pumped from rear chamber into the front chamber because of leaking/damaged seals.
 
Kern Dog said:
While the divorced hydraulic system was supposed to allow the front to work if the rear has a leak (or vice-versa) I've found that if one end fails, the other is terribly inadequate at stopping a car.


Technically, it is not an "emergency" brake. It is a parking brake meant to hold the car still after it has been stopped. For that purpose, they work as intended. In an "emergency", they are not as effective as your regular rear brakes since they only engage the rear brake shoe, not both front and rear shoes.
The fix here?
Replace the master cylinder with the appropriate unit.
Click to expand...

Yep,,,when I first got into stamping back in 92 , the company I worked for made parking brakes .
It took a while to get used to calling them that .
Actually they call them Park Brakes,,it is a term the industry uses .
I’m sure it goes back to potential litigation if someone tries to emergency stop with them and they can’t stop the car ?

I’ve always used my parking brake religiously every time,,just in case .
I’ve never had one freeze stuck on either .

Tommy
 
Bewy said:
Post #7. Unless you just filled that front chamber, where did ALL that fluid come from? Internal leakage inside the m/c. Fluid being pumped from rear chamber into the front chamber because of leaking/damaged seals.
Click to expand...
I haven't filled it yet, I thought they were supposed to be thay full, I can try pumping it with the cover off and look and see if it fills the other side more I suppose. Also if the parking brake is only for the rear brakes that might explain both of my issues, my rear brakes might just not work
 
NO
All you will accomplish is spraying brake fluid on the engine bay
 
Do NOT pump the brakes with the top removed, you will spray fluid everywhere.
SputnikOne said:
I haven't filled it yet, I thought they were supposed to be thay full, I can try pumping it with the cover off and look and see if it fills the other side more I suppose. Also if the parking brake is only for the rear brakes that might explain both of my issues, my rear brakes might just not work
Click to expand...
Treed!
 
townsend said:
By 1973 more cars were equipped with disc brakes so Chrysler started using disc / drum master cylinders on manual four wheel drum cars. It was a gradual process and took a few years to complete the change on all cars.
This was easily accomplished by using residual valves in both front and rear ports.
Also wheel cylinder expanders were being widely used by this time so there really was no need for residual valves.
Some of the aftermarket companies continued making the old style manual drum master cylinders.
In the 1973 parts catalog the all drum manual master cylinder was #3580209.
Here's a photo of the 1973 master.

Click to expand...

Absolutely correct.

I have been installing the disc master cylinder on drum brakes for decades.
The drums and/or discs don't care what "pump" is supplying pressure.
Bore diameter is only consideration.
New Raybestos 36406 15/16 bore is my go to on ALL mopars.... $60ish
Specially when there's not enuff vacuum for the booster .
The small reservoir pumps are getting hard to find.

Screenshot_20260510-123228.png
 
Last edited:
Master cylinder seals finally gave up the ghost… just replace it and bleed the brakes.
 
Desoto291hemi said:
Yep,,,when I first got into stamping back in 92 , the company I worked for made parking brakes .
It took a while to get used to calling them that .
Actually they call them Park Brakes,,it is a term the industry uses .
I’m sure it goes back to potential litigation if someone tries to emergency stop with them and they can’t stop the car ?

I’ve always used my parking brake religiously every time,,just in case .
I’ve never had one freeze stuck on either .

Tommy
Click to expand...

I have to disagree.
If you look at your " vehicle code", for your area, I have gone to many different States codes to prove this to be true .
"Every vehicle had to have a " a secondary mechanical brake " in case of primary brake failure,"
For years it was called "emergency" brake.
Manufacturers changed the name to PARK, when they couldn't fit "emergency" onto that tiny pedal.

Think about how many times your "park" brake wouldn't hold backward downhill, you curbed your wheels, - also part of drivers manual.

How many times you backed outta a parking space and tried to drive forward, but got nowhere till you released the emergency, made to arrest forward motion, why didn't it hold when you backed-up?
Think about it. .

True "park brakes" were installed on the driveshaft, to prevent rotation either direction, as trucks etc.
Cheers
 
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I’m not going to argue with you .
We built millions of park brakes for GM and Chrysler all those years .
All I know is that in manufacturing,,,they were called Park Brakes .
This company moved here from Detroit and Toledo Ohio .
Brought all their original tools and presses with them back then .

Tommy
 
Tennessee
Motor vehicles (not motorcycles)
  • Must have brakes adequate to control movement, stop, and hold the vehicle.
  • Two separate means of applying brakes, each effective on at least two wheels.
  • If the two means are connected, they must be designed so failure of one part does not leave the vehicle without brakes on at least two wheels Justia Law+1.
Apologies to OP
 
Last edited:
The next steps are to
(a) check for leaks, especially the hoses.
(b) start prepping the flare nuts for removal.
(c) Get the tools and/or experienced person to help with breaking the nuts free without damaging the tubes. Otherwise you will be replacing the tubes. And compression fittings are NOT an acceptable repair of brake lines.

The reasons the rear braking was largely ineffective with the front brake resevoir empty has much to do with how the master works. See page 1 of the Brake Hydaulics MTSC linked earlier.
 
Hey again, been waiting for parts to arrive, but I believe im ready now to begin this probably painfull process. My first issue is I dont have a vice, and everywhere I look it says I must bench bleed the replacement MC with a vice before I install it in the vehicle.

I've checked my hoses and I dont see any leaks, so im willing to continue with them the way they are. I have one of those standard brake bleeding kits with the adapters and the hoses and bottle and stuff, as well as access to a handheld vacuum pump if that method would work better in your opinion.

I've seen somone bench bleed the MC by installing it and using the brake pedal to actuate it, but I've also heard that that doesn't fully work, I'd like to hear your opinions on the matter, and if required, maybe some tips for bench bleeding without a vice.

Thanks in advance.
 
SputnikOne said:
My first issue is I dont have a vice, and everywhere I look it says I must bench bleed the replacement MC with a vice before I install it in the vehicle.
Click to expand...
you can "Bench Bleed" mounted on the car. IT just needs to be fairly level jack up the rear of the car if need be. Have someone else press the pedal so you can control the fluid level etc. and have them press and release the pedal really slow. be prepared to have spillage so have towels etc. under the master while you do the "Bench Bleeding"
 
SputnikOne said:
I've checked my hoses and I dont see any leaks, so im willing to continue with them the way they are. I have one of those standard brake bleeding kits with the adapters and the hoses and bottle and stuff, as well as access to a handheld vacuum pump if that method would work better in your opinion.
Click to expand...
the tried and true is down, open the bleeder, close the bleeder, up (SLOWLY), down, open the bleeder, close the bleeder, up (slowly) and keep doing that till no more bubbles from that line longest first RR, LR, RF, then LF.

BE SURE keep an eye on the fluid level in the master, if it gets too low you have to start from the begining.

SputnikOne said:
I've seen somone bench bleed the MC by installing it and using the brake pedal to actuate it, but I've also heard that that doesn't fully work, I'd like to hear your opinions on the matter, and if required, maybe some tips for bench bleeding without a vice.
Click to expand...
It works just fine and just the same as in a vice BUT the master needs to be level
 
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