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Author Topic: Poor Brake Pedal  (Read 3953 times)

Steve

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Poor Brake Pedal
« Reply #15 on: March 14, 2012, 04:11:33 PM »



It's in line with. the wheel cylinders.  But their are bends that go up slightly.  Did I mention I jack the ends up if needed?
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Poor Brake Pedal
« Reply #16 on: March 14, 2012, 04:43:46 PM »

Anything to help in the initial bleeding correctly.
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Gary Buckley

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Poor Brake Pedal
« Reply #17 on: March 18, 2012, 06:51:17 AM »

Hi everyone .Well I have tried bleeding again.As suggested I bled the system using the no pump theory and at the same time I elavated the vehicle in favor of the master cyclinder as its under the floor.When bleeding I noticed that I had some pedal in the rear because of the pedal dropping when opening the bleeder screw.No air came out with ten bleeds per right wheel.I then proceeded to do the same on the front .When opening up the bleeder screw here I have fluid coming out but almost just a gravity flow and no rush of fluid.Also no pedal drop after ten bleeds per wheel.At the end of the bleeding session i have no more pedal than before and noticed no air coming out.When I had the front drums off adjusting the front shoes ,I noticed that there are very large wheel cyclinders on the front.Is it possible that they are too big for my master cyclinder I purchased? The rear Ford cyclinders are normal size compared to the original 1941 Chrysler cyclinders on the front.Thanks again


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Gary Buckley

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Poor Brake Pedal
« Reply #18 on: March 18, 2012, 08:39:30 AM »

Hi Again.I just measured the original mastercyclinder bore and it is about 1 1/8 inches in dia and the stroke is an inch.I will have to jack the car up later and measure mine .I know my stroke is only 1/2 and inch for sure.




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Poor Brake Pedal
« Reply #19 on: March 18, 2012, 12:39:26 PM »

That's how my Nash is set up and the rear brakes will lock up easily if too much pedal is given, so a porportioning valve will be needed to fix that. At his point I would consider there being a problem with the master cylinder itself. If you are pushing fluid all the way through without any air coming out, not enough fluid seems to be pressurizing.
 
Do check one thing, that the brake lines are being routed so the front reservoir is going to the rear brakes and the rear one is going to the front brakes, and does this thing have a porportioning valve incorporated into it?
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Gary Buckley

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Poor Brake Pedal
« Reply #20 on: March 18, 2012, 04:50:20 PM »

At this time I am awaiting an answer from the company that I purchased the brake system from. In their diagram they show drum to drum with a dual master,with the Line closest to push rod feeding rear brakes.The info I read online says that a firewall mounted dual master line closest to push rod feeds front.Another article I read says that a master cylinder used for drum to drum has equal compartments and doesn't make any difference,not like one designed for disc to drum .Also they recommend using a metering valve with the drum to drum insed f a proportioning valve.I really don't know at this time what I purchased.It came from Pirate jacks and was a complete pedal included assembly.I have it plumbed now that the line closest to the push rod is going to my front.


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Poor Brake Pedal
« Reply #21 on: March 18, 2012, 05:04:09 PM »

Agree with waiting for the company to tell what is what, being reverse may have been plumbed differently, but either way it should still be able to get pedal, backwards or not, function is still function, it would be porportions that would be wrong, but pressure should still work. As far as the metering valve goes, with the larger and smaller wheel cylinders, that is to balance front and rear more accurately, because you want about 60/40 front to rear, and the different sized cylinders at the wheel will require adjustment to get that proper. Still doesn't explain why you can't get any brake pedal after bleeding unless the plunger inside the master cylinder itself is bad.
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Gary Buckley

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« Reply #22 on: March 18, 2012, 05:37:38 PM »

I removed the boot tonight from the dual master and got my wife to push on the pedal.It is pushing the plunger in between 1/2 and 5/8 of a inch and bottoms out.The cylinder seems to be about 7/8 to 1 "in Dia. Its hard to get a good visual on it being where it is.After about 4 pumps I have not a bad pedal but it wont last.Next time I push it down it is low again.


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Poor Brake Pedal
« Reply #23 on: March 18, 2012, 05:57:15 PM »

That would be leaking cups in the master cylinder itself, they pump up and are able to overcome whatever is letting the fluid pass by the cups inside, sometimes actually able to push the fluid that passes behind the cups back to the correct side, then leaks back when sitting.

To give an idea, my Dad rebuilt the master cylinder on my TR4 because the brake would do this. I found out years later that there were two size cups, .010 difference in cup size, .740 was early, .750 was the next year (1964), but look identical on the outside, and his rebuild had the smaller cups. The brakes would hold, but as you held them, they would bleed down slowly, but always stopped quickly the first time, so I kind of lived with it and never had a problem. Yours seem to be doing the same thing, but the fluid is actually leaking down right off the bat and require four pumps to correct the problem.
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firedome

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Poor Brake Pedal
« Reply #24 on: March 19, 2012, 04:05:57 AM »

I've had bad m/c brand new out of the box. For some reason they seem to have a high failure rate.

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Gary Buckley

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Poor Brake Pedal
« Reply #25 on: March 19, 2012, 03:08:23 PM »

I was contacted by the supplier today and they told me the MC does not have residual valves built in.He said where I am using it as non power brakes that it can be used for drum to drum,drum to disc or disc to disc.I asked him if it had a proportioning valve  and he didn't answer that.I went out today and switched the two lines around on the MC.For some reason I feel like the brake pedal has more travel now.I took the car for a run around the block and it will definitely pump up to give me a good stop.I am going to bleed the circuit again maybe tomorrow evening because I probably picked up some air
 when I had the lines off even though I didn't lose any fluid.I also removed the cover from the MC and slowly pushed the pedal down a few times .There was hardly any movement in the front section but the rear which would be a normal front on one mounted on the firewall erupted 4 inches when slowly pushing on the pedal.Not sure what was happening here as I was just experimenting.


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Gary Buckley

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Poor Brake Pedal
« Reply #26 on: March 19, 2012, 03:08:35 PM »





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Gary Buckley

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« Reply #27 on: March 19, 2012, 03:12:25 PM »

I forgot to mention that my MC has 2 same size sections.Not sure where there is really any difference from front to back when installing lines but I switched to the way the company I purchased from showed in there instructionshttp://www.piratejack.net/index.php?option=com_content&view=article&id=11&Itemid=18


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Poor Brake Pedal
« Reply #28 on: March 19, 2012, 03:24:23 PM »

You say the eruption of four inches spraying fluid happened when you PUSHED  the brake pedal? That isn't right, it is when the pedal is let OFF that the fluid sprays because of the pressure from pressing the pedal and hydraulic pressure. It is backwards, which could indicate one of the plungers was installed backwards possibly, or leaking past the cup and pushing fluid up this way. Here is something you can do to test the master cylinder
 
If brake fluid bypasses a pressure seal on a master cylinder you will get a pedal that fades. To test for this obtain two inverted flare plugs at an auto parts store and plug both master cylinder outlets. Try your pedal. If the pedal is high and firm the master is good. If the pedal fades the master is bad. Replace master as necessary.
 
If in doing this test the pedal slowly loses pressure, it is leaking past the cups.

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Steve

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Poor Brake Pedal
« Reply #29 on: March 19, 2012, 04:54:34 PM »



I disagree on the residual valves.  A Prop valve is a good idea.  They make adjustable ones.  It gets cut into the rear line.  DO NOT UDE COMPRESSION FITTINGS.  Saying that just in case
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