I’m working on a ’69 Dodge Dart. I am experiencing a hard brake pedal. This occurred when I replaced the master cylinder. I replaced the master cylinder thinking that it was the source of a leak. It wasn’t. So I next replaced the rear wheel cylinders after discovering the true source of the leak. Still had a hard pedal. I turned to the front brake shoes as a possible problem and replaced those and turned the drums. Still a hard pedal. Everything checks out visually. The last attempt at a fix was to rebuild the original master that was working perfectly, but that didn’t fix it. The master cylinders seem to be the common denominator. HELP!! Anyone have an idea where I went awry?

Claude

It could be when you fixed the W/C leak, the original pedal feel came back. The leak may have caused the soft pedal.
Did you change out brake hoses? New hoses may not swell like old ones giving a firm pedal.
A bigger bore M/C will give a firmer feel with less pedal travel but if your rebuilt original did the same, that rules out M/C size as the problem.

Cecil

manual brakes are supposed to be like tat

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Slant Cecil: Thanks for help. I didn't replace the hoses. Didn't need to. I think my next step may be to blow the hoses out toward the master with air. Perhaps I got some dirt in the line. Also thought I'd jack up the car to see if maybe one end or the other is not activating the brakes. I doubt this to be true. I checked the bore size on the master as well the new wheel cylinders.. matches specs. As usual I have a problem that defies solution. None of the trouble-shooting ideas seem to fit.

70 valiant: Thanks for the reply. I have three other slant-six A-bodies with the manual 9" brakes. None of them have a particularly hard brake pedal. The Dart in question, by the way is a 57,000 mile original car. The only modification I can see is 2" exhaust. This car goes like H. It really moves for a stocker. Also the suspension is stock and the handling is excellent. It's great to see what these cars were like when new (almost new anyway). Back to the garage floor. Any more ideas?

(Posted by ValiantMan)

Yes.

It is possible your brake pedal freeplay is set incorrectly. I can see youve been around the block Chuck, but it's just an idea. If the MC piston is not allowed to return completely the port is not uncovered to the reservoir and pressure can build up in the line. Usually there is a residual pressure valve that allows some pressure to remain in the lines so the pedal does not have to travel as far to build up braking pressure, but it usually fails open if at all.

Alternately, you could check your proportioning valve. Try swapping it out with a known good one.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Drum brake cars do not have proportioning valves.

Cecil

I have been working with Claude on this and wanted to point out that the braking is hard, ie, takes a lot of pedal pressure. This all started when the cyl. blew and the cyl. and master were replaced. Both of my dad's Darts do not have this problem, so it is not a normal condition.

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Chuck Rivers, Webmaster

OIC, my bad

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Stuck wheel cylinders are the first things to check.
Next thing is to look at the lining (brake shoes) to see if they may be installed backwards. (the large shoe goes to the rear)
There is a chance the the lining material itself is the problem, some of the new lining materials are so hard that their cold stopping performance is poor.
DD

70Valiant,

Please do not put such a large picture in your signature line. It takes quite a while to download.

Thanks,

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Chuck Rivers, Webmaster

The rubber hoses may look ok on the outside, but it is possible for pieces of rubber to come loose inside (from age), acting as a one way valve and causing high effort to apply the brakes, or causing the brakes to not release after applying them. If you have exhausted all your other options, try the hoses.

OK, I guess I should call it a junction block, if it's a dual circuit system there should be one. As I understand there is a valve in there that will shift over if a massive leak occurs in one circuit, to allow the other circuit to continue to function. I'm guessing that if this valve is stuck in the wrong position, it could cause this symptom.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Step, your right about the "distribution block" internals, this piston/valve is what controls the brake light (along with the ebrake switch).

The only difference between the distribution block and proportioning valves on the a body disc cars is that internally they have varying width passages to control the pressure differential.

Pierre, thanks for the info on the "distribution/metering block" i hadn't the slightest idea as to what purpose it served-- besides the "brake" light feature. I ditched mine in two different cars and went straight for the aftermarket adjustable prop. valve-- said topic and action therein generated a **heated** debate on another board.
*laughs*
so anybody need a metering block?
*rubbs hands together greedily*

-JYH
64 Dahht
69 Cuda
SoCal

Eric,

Thanks for the data on the hoses. We are going to pull all the cylinders apart and clean them, then flush the entire system, so we will check the hoses at that point.

On the subject of the distribution, block one thing that is not clear is if, when the piston moves in the block, does it cut off the flow to that part of the system or just activate the light? It appears that the light is burned out, so we need to replace that and then check to see if the piston has moved. If it does block the "bad" part of the circuit, then that might explain the hard braking.

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Chuck Rivers, Webmaster