Brake pedal is really stiff

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ESP47

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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.
 
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.
 
sounds like the master cylinder bore is too big.
big bore= hard pedal
smaller bore= softer pedal, more travel
i have the same problem
 
70Duster440 said:
Bleeding the system might be a good place to start. .
Click to expand...

A hard pedal is the OPPOSITE of a bleeding problem.

Besides what's mentioned, the size of the master bore, there are a few other things----any chance some restriction in the system is stopping flow?

But the OTHER biggie---mentioned the other day---is the fit and quality of the shoes/ drums.

Cheap shoe lining can give poor braking performance

Drums that have worn/ or been turned too large cause poor performance, because only the center area of the shoe lining contacts the drum---the upper/ lower areas aren't doing anything to stop the car, and worse, the "overwork" on the center area of the lining causes it to quickly glaze and become WORSE

Drum wear--drums never wear evenly "flat inside" so that when you put nice new shoes into worn drums, they don't contact evenly across the WIDTH of the drum, causing the same thing mentioned above, but now we are speaking of (typically) the drum wears "dish" shaped ACROSS the drum, and the edges of the shoe tend to hit first.

Last, all the "big three" did the "same thing." On smaller, cheaper cars, with smaller engines--you always got the smaller brakes. You didn't mention what size they were, but if they are say, the little 9" brakes, they WON'T stop as well as "might be expected."
 
67Dart273 said:
A hard pedal is the OPPOSITE of a bleeding problem.
Click to expand...

Yes, but we're trusting he's describing the symptoms accurately and correctly. If the pedal's actually at the end of it's travel with air in the lines there might be enough pressure to kinda stop the car. I'm suggesting he start with the simplest things to check and systematically eliminate common problem areas.

By the same token, an aftermarket MC with 1.125" bore will make for a very hard pedal but not so stiff that you have to wedge your knee up under the column.
 
Also the rubber lines may be collapsed inside. Are they original?
 
If that bore is over 7/8", start there; too big. Pull the drums, are they blue?, look at the shoes, are they glazed or just worn in the center?
Too many fast stops will glaze, drums oversize will show by only the center hitting. My 70 Duster ruined 2 sets of 10" brakes until I went disc and 11" rear.
 
I basically wasted my entire day yesterday. I woke up early and took the master cylinder out. Broke my ratchet getting it out. Bled it on the bench and reinstalled it. Checked and bled the rear drums. Broke my small ratchet on one of the rear drums. Checked the RF brake and repacked with grease. Broke the bleeder screw on the brake cylinder. Went and got a new bleeder screw and installed it (took forever to get that little brake line in between the rubber line and the brake cylinder back in). All the rubber lines look nearly new btw. Took the tire off the LF. Broke my adapter on my impact wrench. Bled that brake and took it out for a ride. Nothing at all changed....I was so pissed I could have driven the car off a cliff. 2 broken ratchets, a broken adapter, broken brake cylinder and 8 hours of work that went for nothing. Brake pedal still only goes down a couple inches and it's really hard to stop because you can't keep applying pressure after that to stop quicker. You really have to mash on the brake if you want it to stop faster.

I'm not sure what kind of master clyinder it is. It's the type that has a bolt holding the cover on, rather than the bar that clips across the top. I also have what looks like a brand new brake booster. Should I install this or just go and get another master cylinder?
 
I bought a brand new Raybestos master cylinder and installed it yesterday. Didn't fix the problem at all.

I have a brake booster off a 73 Valiant. Will this work with my 67 master cylinder or do I need the master cylinder that specifically goes with the brake booster?
 
ESP47 said:
Brake pedal still only goes down a couple inches and it's really hard to stop because you can't keep applying pressure after that to stop quicker. You really have to mash on the brake if you want it to stop faster.

QUOTE]
This sounds like a restriction in the rear brake circuit:
either a collapsed hose or
debris in the proportioning valve.
When bleeding the rear brakes are you getting a good steady stream of fluid out of the bleeder or just a dribble?
Click to expand...
 
I'm getting a good stream. The rubber lines look like they've been replaced during the last 5 years or so as well.
 
I'm thinking about taking off all the self adjusters so I can see how the brakes feel when the shoes are a little looser.
 
Man...nothing is working. The pedal is still too hard to push and even harder to hold down. Does anyone have any idea what could be going on? The master cylinder didn't do anything. The self adjusters only slightly helped. I can't think of anything else. All the rubber lines and metal lines look ok and aren't kinked. Could it be the prop valve?
 
Your booster could be bad !

Mine just went bad, and believe me when the booster isn't working you really have to push to get the car to stop.
 
Go back up and read my post. If the master is the correct diameter, as are the wheel cylinders, it could be a plugged line--which you can easily check by bleeding,

or POOR DRUM SHOE FIT

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.

Also along this line, the lining--because so little of it has been doing any work stopping the car--will have become glazed and LESS effective

NEW shoes on "overturned" drums WILL NOT FIX THIS

Here's how you "used" to fix this:

Sometimes, local reliners could "shim" brake lining or install oversized lining

You had a grinder called an "arcing machine" that would "arc" the shoes to fit the oversized drums

Nowadays, you probably cannot do this. You will have to get new shoes--or at least sand the glaze off yours--and replace the drums.

Arcing machine picture I found on the www

pict0044.jpg


ALSO if you DID NOT have the drums turned when you replaced the shoes, you can have all sorts of "poor fit" issues:

http://www.autozone.com/autozone/re...= 0900c15280213fb3&subtitle=out-of-round drum
 
Yeah the brakes seemed to bleed out fine. I can try swapping my Duster's drums with the Valiant's and see if that makes a differece. The shoes themselves look fine. If none of that stuff works, think it could possibly be a wheel cylinder issue? Has anyone ever put the wrong wheel cylinders in and had a problem like this?
 
ESP47 said:
I can try swapping my Duster's drums with the Valiant's and see if that makes a differece. The shoes themselves look fine.
Click to expand...

Look, you are not listening, and throwing parts around doesn't solve anything.

You need to INSPECT the drums you have to see if they are:

turned out too big

worn "bellmouth" or "round top" or other wear patterns

The only way I know of to do that is put them on a (brake) lathe where you can center them up and run a tool across the surface to test for wear

You need to see if the shoes fit TIGHT in the drum, and the only way to do that is to remove the shoes and trial fit them in the drum. See if they appear to "sit flat" in the drum, whether they "rock" to and fro, indicating drums worn are larger than the shoes

I would agree that you might use a second set of drums for comparison, but just swapping them won't prove a thing.
 
I appreciate you helping but I am not understanding your logic.

First, I have been listening and I have inspected the drums on more than one occassion. No over turning, no strange wear, no grooves, no nothing that tells me the drums are the problem. The shoes just have the normal slight glazing as well as normal wear. Either way, I'm still going to see if the drums are possibly the problem.

I don't understand how using a second set of drums for comparison is better than "throwing parts at it" and swapping in a known good set of drums to see if that was the problem. I don't have a brake lathe to test for wear so I'll just troubleshoot the drums by putting my Duster drums on and seeing if the braking feels any different. It's free and only takes about 45 minutes.
 
OK, you clearly did not understand what I'm getting at. You can't just throw your second set of drums on there and really tell anything, unless you get incredibly lucky. If they are worn out some, they might just have the very same problem

Once more, THE ONLY WAY you can see if the drums are oversize or worn badly is to remove the shoe from the car, and place it in the drum where you can SEE it and see how it fits, critically. REALLY take a look at it and see if it fits in there tight, or whether it "rocks."

I realize you probably don't have a lathe, but you'll have to take at least a couple of the drums somewhere that does. Just tell 'em you are having poor braking troubles and you want to know if they are worn oddly or turned out too far. They can "mike" em and check them. You can check for several wear conditions by putting a straightedge across the drum surface. Trying to check for "bellmouth" is a little harder, that's why a lathe works good. If you have a good combination square, you can get a good idea by laying the straightedge across the back of the drum, and let the square shoe down inside against the wear surface.

Here's the thing: Manual drum brakes have been around a VERY long time, and they don't operate by magic. There are strict known principles by which they work, or don't. What you are describing sounds exactly what I've been harping on --poor fit of shoes and drums, or glazed or poor quality lining.
 
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.
 
I assume you verified that the shoes are on correct - short lining on fwd side, long lining on rear side, though wouldn't explain your problem. I agree it doesn't make sense, but "push hard" is qualitative. My 69 Dart had 9" drums w/ manual MC and I don't recall a problem pushing hard enough to skid, plus my wife drove the car. An MC with a smaller piston would make it easier and give the pedal travel you expect.

As a thought, the 10" drum brakes in my 65 Dart are easy. I installed a junkyard booster and MC from a 99 Breeze on 73 Dart brackets w/ proportioning valve for the rear line (plan front discs).

I know more work, but maybe disconnect at each wheel cylinder and blow out the lines w/ air, to insure no rust clogs. I use silicone brake fluid since I have seen massive rust gunk clogs in cars with regular fluid. If you do that, blow alcohol thru to clean the lines then air to dry them. Some diss silicone for often strange reasons, but the U.S. military uses it.
 
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