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P15 brake pedal pressure


cerick305

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I've noticed my brake pedal seems to be soft initially then the second press its normal pressure. I figured I had air in the lines. I bleed the lines starting on passenger rear, driver rear, passenger front, and finally driver front. Took it for a drive, and same thing. Initial press it is softer than the second. So I figured I didn't bleed the lines good enough. So I did it again with same results. I don't have any lines leaking and master cylinder seems leak free.

Now when I say the initial press is soft, the vehicle still breaks fine. But there is a definite hard pedal feel on the second press. Then after a few moments (10 seconds or so) without pressing pedal then the pedal goes back to its softer press.

Anyone have any ideas?

What I did was open the brake blender valve after hooking plastic hose up to it pitch upward to trap brake fluid on valve and air would rise up. Then pressed brake pedal 4-5 times. Looked and hose had filled with brake fluid and then I tightened bleeder valve. Then checked and refilled master cylinder. I did this process over for the other three brakes.

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I did not check the show adjustment. But what would that have to do with the initial pedal press to be soft then the second pedal press to be harder?

Too much space between shoes and drum to get a good pedal the first time? Can't really explain it but I had that on my pickup and I adjusted the shoes and it went away.

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Adjustment and/or travel issue. Air is spongy, pump up is adjustment/travel. Lots will tell you air but just isn't so. Make sure your master cylinder rod adjustment is correct and than your brake adjustments.

Earl

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Hey Cerick,

 

I/ve got the same deal on my brakes. Chances are your back brake shoes are not adjusted right. The bottom line is your shoes, when adjusted properly, are only about 1/16 of an inch from the drum. If any shoe is more than that, it takes more fluid to move the piston on the wheel cylinder further out to take up the space between the shoe and the drum. Your Master cylinder only moves so much fluid per push of the brake pedal. When the brakes are adjusted right it will only take about 1/4 to 1/3 of pedal to have firm brakes. The reason after 10 seconds or so you have to pump again is because the brake shoe return springs pull the shoe back to the full retract position.

 

The fronts on my P-15, I can dial right in. The back brakes need the AMCO tool to do it right. The fronts can be adjusted easily because taking the drum off is easy and you can adjust the major and minor with very little trouble, but the back needs a puller to remove the drum and then you adjust the major adjustment and re-install the drum then adjust the minor adjustment. Because the cars only had the single master cylinder, the pressure will only be firm on the first pump when all shoes are in adjustment. My back shoes are out just enough to require 2 pumps for a firm high pedal. So I drive really conservative. I would anyway so some clown doesn't plow into me or me into them from them not paying attention.

 

Joe 

Edited by soth122003
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I was about to re-bleed the lines and noticed a small crack in one of the hoses.  I took the hose into Napa and autozone looking for a replacement.  However, I could not find one.  Anyone have any ideas?  I think the female end is 3/8" NPT and hthr male end is 'possibly' 7/16".  see picture....

post-8119-0-68396000-1459126270_thumb.jpg

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Rock Auto has both front and rear. hoses...

That's where I buy old Mopar brake parts from now days as they have great cataloging and prices plus fast shipping....http://www.rockauto.com/en/catalog/plymouth,1947,p15+deluxe,3.6l+218cid+l6,1486706,brake/wheel+hub,hydraulic+hose,1792

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OK here comes the Brake catalogs again to the rescue.  Getting and having the various catalogs in your literature is important.

 

As per my EIS brake catalog:

 

P)lymouth p15  1946-48

 

Brake Hoses  front    SP967  rear SP790

 

This would be a TYpe 2 hose  7/16" by 20 threads  and the other end is 3/8" by 24 threads

 

SP967  is a total of 11 1/8 inches

SP790  is 16  27/32 inches

 

I have other major information on brakes on my catalogs that I have scanned and this should be in you collection of information.

 

Contact me for the information.

 

Rich Hartung

Desoto1939@aol.com 

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He might just buy them from RA and re sell them to you!

RA sometimes has some really good deals on Raybestos brake parts. I get twice a year huge discounts on discontinued parts. 

Last 2 deals were flathead new "Gates" water pumps and raybestos full set (6) of wheel cylinders @ $100.00...USA stamped too.

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