Need help troubleshooting problem with brakes

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dterry1

dterry1

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Ontario, Canada
Hello, I just picked up a 72 Duster and am having some problems troubleshooting the brakes
(All 4 are disc brakes)

Here's my issue:

The brakes are mushy, and the brake pedal doesn't travel very far when pushing it all the way down
When I completely depress the brake pedal, the car just comes to a stop while on the slant of my driveway

I bled all 4 brakes today, checked for any leaks in the lines
Bleeding the brakes improved them a bit, but not to the point where they are working good
I checked the seal on the master, looked to be fine
When I pump the brakes while the car is off, the pedal stiffens to an extent, but doesn't go completely solid
And then after starting the car the pedal slowly and slightly unstiffens

If anyone has any suggestions on what I should look at next, that would be extremely helpful
I ran out of time today but tomorrow I plan on looking to see if the calipers aren't moving properly, or need to be lubricated.


Any help/suggestions are much appreciated
Thanks
 
power or manual brakes?

type of brakes? OE disc/drum, drum/drum, aftermarket something or other?
 
Check all the caliper slides make sure there not siezed up, and try a gravity bleed , you can also pinch the hoses off to see if the master leaks down
you should have three or four hoses two in front and one or two the rear. The brake pedal should be hard and not sink down. if that's good then do a normal brk/bleed
farthest one first. Also check if there is combo valve on it lightly tap on it with a hammer the valve inside could be stuck.
 
Bleed more.

Did you...

  1. Change the master?
  2. If so did you PROPERLY bench bleed it?
  3. Did you remove the residual pressure valve from the drum circuit if using a stock disk / drum master cyl
  4. Tell us more about your rear disks
  5. What brand what type of e brake
  6. Did your power brakes work properly before your change to 4 wheel disk
 
First, that likely DID NOT HAVE disk brakes, and most certainly not 4 wheel disk. So for starters ARE YOU CERTAIN that it has disk at all (front) and that the rear are also ??

If so, next, make certain the bleeder screws are at the top of the calipers. It is common to reverse the spindles to put the calipers to the rear of the spindle, and so you must swap the calipers side to side to get the bleeders "up."

Next if you find you actually have rear DRUM brakes, adjust them up tight and then re-bleed, see if the pedal improves, then back off the brakes untill you can turn the wheels. The brakes WILL drag some until seated.
 
What @67Dart273 said. If it is 4 wheel disk brakes, the rear disks were added by a previous owner. Did he use the right master cylinder?
 
One of the problems with bleeding brakes in old cars is this. Detroit used their wonder metal, cast iron, for a lot of m/cyls. They rust from moisture absorbed, build up a rust pile in the mcl. When you bleed the brakes, bottoming the pistons in the mcl, seals get ripped when they pass over the rust. Then strange problems occur. Not saying this is the problem, but when everything else checks out, it is likely time for a new mcl.
 
Dana67Dart said:
Bleed more.

Did you...

  1. Change the master?
  2. If so did you PROPERLY bench bleed it?
  3. Did you remove the residual pressure valve from the drum circuit if using a stock disk / drum master cyl
  4. Tell us more about your rear disks
  5. What brand what type of e brake
  6. Did your power brakes work properly before your change to 4 wheel disk
Click to expand...
1. Haven't changed the master
2. Fully flushed the brake lines.
3. Yes
4. I will have to look at the specifics, just picked the car up this past weekend.
5. Same answer as 4
6. Previous owner changed to 4 wheel disk, brakes worked fine, car sat for a year or two, and here I am
 
67Dart273 said:
First, that likely DID NOT HAVE disk brakes, and most certainly not 4 wheel disk. So for starters ARE YOU CERTAIN that it has disk at all (front) and that the rear are also ??

If so, next, make certain the bleeder screws are at the top of the calipers. It is common to reverse the spindles to put the calipers to the rear of the spindle, and so you must swap the calipers side to side to get the bleeders "up."

Next if you find you actually have rear DRUM brakes, adjust them up tight and then re-bleed, see if the pedal improves, then back off the brakes untill you can turn the wheels. The brakes WILL drag some until seated.
Click to expand...
Certain it has all 4 disk, they were swapped by previous owner when they rebuilt the motor. Bleeders are at the top of calipers.
 
To isolate a hydraulic problem from a mechanical one, having bench-bled the master;
remove all the wheels and remove all the calipers.
Get some HD C-clamps, and jam those pistons into the bottoms of the calipers. If the rears have a parking brake system involving the caliper, make sure it has been backed off and cannot interfere.
Now simply step on the brake pedal.
With manual brakes, the pedal should be almost instantly hard.
With a booster you will have to start the engine to evacuate the power chamber. With a booster you can expect about one inch of pedal travel before it gets hard.
If the pedal does not get hard the first thing to test is to make sure the master is properly bled, and that the pushrod depth is
correct.
Be advised that when you are clamping the pistons, this will drive fluid back up into the M/C. It can happen that the M/C overfills and you get a mess. Most brake fluids will attack your paint. Do not leave the lid off. If there is air in the system, the returning fluid can cause a geyser in the fluid that is well able to hit the underside of the hood.
After the hydraulic system has been proven to be working properly, then you can move to the mechanicals.
 
Last edited:
Just a suggestion for the future:
When you need help with a problem on a car forum, you need to provide all the information regarding the problem.
The way you did it, there are several unknown issues that require members to ask you questions. This isn't the way to do it.
Don't make it hard for people to help you. To log on and ask a basic question like what is wrong with my brakes yet provide zero info about the brand of the parts, the type of parts or anything that might help....isn't going to help you.
No pictures either? Why?
If you're going to be stingy with information, at least provide pictures so that maybe someone can tell what you have.
This entire forum is made up of voluntary members. Nobody is paid to answer questions.
Nobody here knows your car so we are all in the dark until you provide info.
I read nothing about the type or brand of master cylinder, you hinted at it being a power system but didn't clearly state it. No mention of the type of rotors, calipers, brake hoses, whether it has a proportioning valve or not or even the brake pads.
Maybe you don't know the details. If that is the case, state it up front but tell as much as you know so others can help.
There are numerous great people on the site that will chime in to help. You have to make it easy for them to do so or people will scroll on by this topic and you'll never get the help you need.
 
AJ/FormS said:
To isolate a hydraulic problem from a mechanical one, having bench-bled the master;
remove all the wheels and remove all the calipers.
Get some HD C-clamps, and jam those pistons into the bottoms of the calipers. If the rears have a parking brake system involving the caliper, make sure it has been backed off and cannot interfere.
Now simply step on the brake pedal.
With manual brakes, the pedal should be almost instantly hard.
With a booster you will have to start the engine to evacuate the power chamber. With a booster you can expect about one inch of pedal travel before it gets hard.
If the pedal does not get hard the first thing to test is to make sure the master is properly bled, and that the pushrod depth is
correct.
Be advised that when you are clamping the pistons, this will drive fluid back up into the M/C. It can happen that the M/C overfills and you get a mess. Most brake fluids will attack your paint. Do not leave the lid off. If there is air in the system, the returning fluid can cause a geyser in the fluid that is well able to hit the underside of the hood.
After the hydraulic system has been proven to be working properly, then you can move to the mechanicals.
Click to expand...
To add to this, and you can do this if replacing the pads, get some method lined up to first suck some fluid out of the master, so that there is room for the fluid. I actually bought a couple of big old medical syringes off ebay BUT THEY ARE GLASS. You can use them with about anything and it won't hurt them, unless you drop them.
 
67Dart273 said:
To add to this, and you can do this if replacing the pads, get some method lined up to first suck some fluid out of the master, so that there is room for the fluid. I actually bought a couple of big old medical syringes off ebay BUT THEY ARE GLASS. You can use them with about anything and it won't hurt them, unless you drop them.
Click to expand...
i use a plastic dirt bike fork oil syringe, they do a great job of containing the fluid and super cheap. what's great is that you can just toss 'em in the slop sink to rinse and not sweat it, and if they get all nasty you can just throw them out.
 
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