Brake pedal is really stiff

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Just an update...

Had all 4 drums turned. Bought new shoes, they all fit perfectly. Pulled all wheel cylinders out and replaced with correct Raybestos cylinders. Bought original Raybestos master cylinder. Bled MC, bled brakes and still have the exact same problem. Car is going to be taken into a shop as soon as I get some money for it. I'm fed up with this. It should not be this difficult to get a damn drum brake system to work correctly. There has got to be some kind of built up pressure somewhere because the pedal is stiff and doesn't want to be pushed down very far and the brakes are really weak. I don't even think I could lock them up if I tried. Yet when I bleed them the pedal will drop to the floor once I open the bleeder. It just makes no sense.

These things almost always turn out to be something stupid and overlooked. Now that you've replaced virtually all the major components, here are a couple more ideas for you:
Correct pushrod or master cylinder used?
Pushrod seated correctly in recess of master cylinder?
Pushrod retainer seated in it's groove on the pushrod (manual master cylinder)?
Pinched, crimped, or bent hardline?
Pinched, crimped flexline (hose). Flexlines can also appear perfect on the outside and be broken or collapsed internally enough to block fluid flow. It might be possible for a bad hose to block under pressure and still allow fluid to flow in a no pressure situation (like bleeding).
Might not hurt to check the condition of all junction blocks and line fittings to make sure you are not getting a blockage at one of those.
 
bleeding the system might be a good place to start. Also, it would be good to know what the previous owner installed for a mc - whether it's a stock application or they put something on like a truck mc that has a larger bore. The larger the bore, the more pedal effort is required.

x2
 
You said in your original post that the pedal travelled like 2 inches "Only goes down a couple inches". That's too much. Lord knows why you think it's too little. Not to be mean but just take it to a good brake shop.
 
....just to substantiate my statement...

I had a brake booster go bad (vacuum leak) and the brakes continued to work but the peddle was a bear to push and hold just as you describe! "Knee under the steering wheel" to hold, Replaced booser and right back to normal.
 
WHEN DID this problem start ??? what was done to make all this happen??? start from there.,...and what type of perportioning valve do you have ?? a junction block or a metered valve ??

heres some thing to try,,,,put the car on jack stands remove all the tires and brake drums,,,,get some one to push the brake pedal slowly,,and see ho wmuch the brake shoes move for starters,,,dont push the pedal to hard or to fast,,,,
 
OK, I missed the manual part. Does the brake light come on? valve needs to be re-centered.
 
Quote 67Dart273

" To repeat. IF THE DRUMS have been turned too far oversize, the shoes will now "in effect" be too small. This means they are only touching in the center of the arc of the shoe, and very little of the shoe surface is doing anything".



Just an update...

Had all 4 drums turned. Bought new shoes, they all fit perfectly. Pulled all wheel cylinders out and replaced with correct Raybestos cylinders. Bought original Raybestos master cylinder. Bled MC, bled brakes and still have the exact same problem. Car is going to be taken into a shop as soon as I get some money for it. I'm fed up with this. It should not be this difficult to get a damn drum brake system to work correctly. There has got to be some kind of built up pressure somewhere because the pedal is stiff and doesn't want to be pushed down very far and the brakes are really weak. I don't even think I could lock them up if I tried. Yet when I bleed them the pedal will drop to the floor once I open the bleeder. It just makes no sense.


Thanks for explaining the arc of the shoes 67Dart273. Some folks here seem not to understand. If you turn the drums, they get larger and the shoes don't fit inside as well and don't grip as hard. I bet I could had slip some feeler gauges in parts of the brake shoes when you pressed them against the walls of the drums. If they were turned they are now larger inside and the arc is off.

It might not be the main problem but you should had brought NEW brake drums that are smaller - tighter inside. It would had grip better

Thanks again 67Dart273

I'm buying new some new - but older stock - brake drums for my back brakes. Sure glad I didn't waste $ turning the drums. Guess rotors can be turned but not drums - just not too much, better to just replace.

BTW, you can not tell if a brake hose is collapse by looking at the outside of the hoses, again might be the problem, might not be but you can't tell by looking at the outside of the hose. The fluid could had weaken the inside of the hose, gets mussy and doesn't flow fluid easily
 
.....Yet when I bleed them the pedal will drop to the floor once I open the bleeder. It just makes no sense.
Chances are that you toasted the new Master by Letting the pedal go all the way to the floor. Always put a block of wood under the brake pedal stopping it at the most 1/2 way when bleeding. I would bet your problem is the proportioning valve but may as well get a new master again too and hoses. If the adjusters are not adjusted way far out then the Drums aren't too far gone. With new shoes, there should only be about 1/4 of threads showing on the adjusters. If you're seeing like an inch or more of threads then that indicates drums are reaching the end of serviceability.
How were the brakes before before all of the new parts were put on?
 
As Far as the Drums go, there is a spec for the serviceability of the drum. The Max I.D. Is stamped on the Drum. The person resurfacing the drum should have checked it before and after. They sould only have taken of a tiny bit to De-glaze the Drum. Unless they were clueless and took way way too much meat off the drum, Then that's probably not your problem. Especially with new shoes to fill the void. Also, The design of the Shoes and Adjusters is such that the shoes will remain close to a perfect circle as the shoes wear. The shoes "slide" lightly as they wear keeping them "round" in side the drum. Check the drums with a Micrometer and tell us the measurement. If they are in spec or close to it then you should be able to get great stopping power. Also, You can jack up the car and have a helper step on the brakes and try to spin each wheel with the brakes applied. This will pinpoint a problem and point you to which wheel position has the problem. This is also the time to make final adjustments to the brakes. You keep adjusting and the helper keeps pumping the Brakes to center the shoes in the drum.
 
The M/C will get toasted if the pedal goes down too far. Hmm, you mean the seals inside the bore might get ripped if the travel outside the bore in a rough casting ?
 
The M/C will get toasted if the pedal goes down too far. Hmm, you mean the seals inside the bore might get ripped if the travel outside the bore in a rough casting ?
That's how I was trained. Never go past 1/2 way when bleeding or seal damage will occur. I'm not an expert but Consider my mentors and teachers to be among the best so I just always did what they taught me no questions asked. Back In the day we just stuck our left foot under the brake pedal and pushed till we hit it lightly. About 1 1/2" or so max. My bet is still on the Prop valve, or Wrong Shoes, Or improper installation of shoes/Hardware.
I don't believe we even have enough to go on because we don't know the full sequence of events that led up to the problem. Or even how the brakes were before the Brake job.
 
I let my master cylinder go all the way to the floor when I bleed my brakes which I do about every two years. Never had a problem.

And just putting on a master cylinder the parts store books say to use is not gonna cut it. Figure out what bore you currently have and post that size up. On my car it came originally with a 1" bore and one needed two legs to stop the car. And that was with everything in the entire brake system replaced, including hard lines, and pressure bled. Swapped to a smaller bore problem solved.

Also, size of wheel cylinder bores would be good to know too. Kinda tough to figure out what you have over the internet without all the info. 9" or 10" brake system?
 
Oh wow I didn't think anyone responded to this.

The MC is the original type to the car. I can't recall the number but I even had Dan give me the info on which MC to get to make sure it was the correct type with the correct bore size.

I'm not sure what you mean by 2" of travel being too much. Are you saying your brake pedal only travels about 1" when you press it? That doesn't give you much of a feel between light braking and locking the brakes up. My Duster has the exact same 9" brake setup and the pedal travels about twice as far as the Valiant's pedal. The Duster brakes feel great...for drums at least.

The brakes have never felt good since day 1. I bought the car without an engine and once I got it running, I noticed the brakes just felt like crap. This was before drums were ever turned on it. There has been absolutely no change in the brakes after everything I've replaced. You can tell that the brakes are bad just by pressing the pedal without the car moving. If the drums were turned too far and the shoes weren't touching the drum, you'd think there would be excessive movement in the pedal because the shoes have farther to travel. It feels as if I have the opposite problem.

I had no idea the rubber hoses could collapse from the inside without being visible on the outside so that's another thing to check. I've always wondered if it was the prop valve as well. Wouldn't that affect bleeding though?
 
I've always wondered if it was the prop valve as well. Wouldn't that affect bleeding though?

Probably not a bunch, BUT if you bled the brakes and was pushing the pedal tight to the floor you may have off centered the valve. If I remember correctly you can loosen one of the lines at the proportioning block and have someone push the pedal until you hear a click and tighten the line. You just re-centered the valve.

When you bleed your brakes put something like a 1 inch piece of wood under the pedal so you don't completely bottom out the pedal.
 
I put new shoes and bled the brakes on this 67 Valiant before I got it on the road. After driving it for a while, I noticed the pedal is really stiff and only goes down a couple inches. When sitting at a light I was having to wedge my knee up under the column because the pedal was so hard to keep held down. It has manual brakes and the engine isn't idling too high or anything. I'm thinking maybe the master cylinder wasn't bled by the owner before me. What do you guys think? I can't think of what else it might be. Just want to get a little more info before I start tearing into stuff thats unnecessary.

I had the same problem a few years ago on my sisters road runner in the end I fixed it with a adjustable master cylinder rod. You can get it at jegs for 40.00 part # A21161 or a884-a1726 54.00 I don't remember which one I out in it's been to long. It did fix it though with this rod and a little adjusting. Good luck.
 
You changed the shoes. Did you change the slack adjusters also. They are right and left sensitive. You could be adjusting losse instead of tight.
 
Did some work today on the brakes. I swapped all the drums and shoes from my 71 Duster on to the 67 Valiant and drove it around. The good news is that the brakes worked much better. What I mean is when you mashed on the pedal, the car really stopped. Before it would have to roll a little bit like it gradually wanted to stop. The bad news is the pedal still felt way too stiff. There was just no feel in the pedal like I normally get from my Duster. I inspected all the original shoes from the valiant and they're all newer shoes. Can't have more than 500 miles on them. They all looked great except the drivers left front shoe. The larger shoe had a spot up near the top almost like that's just about the only part of the shoe that touches the drum when stopping. I'm guessing that's the culprit for the brakes feeling weak, but there's still no solution for how stiff the pedal feels.

I'm wondering if a 71 Duster master cylinder would work? Are there any differences in 67 Valiant MC push rods vs. a 71 Dusters?
 
Pull the master cylinder loose from the firewall to confirm the bore diameter.

You can always install a 15/16" bore master if you want a lighter pedal.
 
Pull the master cylinder loose from the firewall to confirm the bore diameter.

You can always install a 15/16" bore master if you want a lighter pedal.

The one in the car right now has a 1" bore. Will going from 1" to 15/16" really make a noticeable difference?
 
The one in the car right now has a 1" bore. Will going from 1" to 15/16" really make a noticeable difference?

It actually can make a difference. It's a Pascal's law sort of thing. Still catching up on the thread, but I gotta make a note here. You shouldn't have a proportioning valve in an all drum brake system. You will only have a metering block that will sense a pressure differential if you develop a leak.

Have you grabbed your trusty FSM, sat down with a beer and just double checked everything? How does the fluid flow when you bleed the brakes?
Sorry if those questions have been asked. I am trying to catch up here.
 
Yes, 1/16" difference in bore size will make a difference.

Did you measure the bore to confirm what you actually have?
 
I'd be looking for a 7/8" bore, and yes, you'll see a real difference.
Someone else just recently made a post giving a part # ...
Search the forum for it.
 
My first thought reading your saga was a common hard pedal problem caused by stuck wheel cylinders. I agree with 67Dart273 that there is still an obstruction in the system somewhere now that all wheel cylinders have been replaced. If the brake pedal won’t depress when connected to system something is not moving fluid or pistons.

First place to look for fluid flow problems are the soft lines which if of fairly recent manufacture will that date on them. If no date or ten years old or more replace them, they are not safe. These lines may look nice on the outside, but can be mush on the inside or have chunks of loose lining acting like a foot valve preventing flow a result of age and contaminated brake fluid. And, as suggested previously, check distribution block for crud as well. These are the two remaining components you have not addressed.
Generally poor stopping performance indicates front brakes are not working very well as they do most of the work.

Diagnostic department:
Air in hydraulic system will compress when brake pedal is depressed giving a mushy longer pedal travel which translates to less force applied to brake shoes or pads resulting in long stopping distances. Fluid will not compress unless heated to boiling point.

Parts not moving such pistons in cylinders or calipers, improper fitting shoes or friction compound, and blockage of fluid flow will cause hard pedal.

Drums and rotors turned beyond design thickness cause a low pedal because the friction material has to travel too far to make contact with drum or disk. This will result in unsafe slow application of brakes and longer stopping distances.
 
Thanks for the replies guys. Yeah I made a mistake calling it a prop valve but you know what I mean. I did measure the bore size when I put the MC in a few months ago and it was 1". It bleeds fine. Only problem is once the system gets most of the air out, the pedal becomes hard as a rock.

I'm obviously no expert but I've managed to keep my Duster's 9" brake system running fine for 10 years now as my daily driver. The only real difference in that system and the Valiant's system is a 1/16" difference on the MC bore size. I wonder if that could just be the only problem?

I'll research that 7/8" MC, thanks!
 
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