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1948 Plymouth Special Deluxe Master Cylinder problems

brakes floor boards master cylinder p-15

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7 replies to this topic

#1 MattWalker


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Posted 04 January 2012 - 07:20 PM

So I got a 1948 P15 a couple months ago and realized the brakes weren't doing so well. I replaced all the wheel cyliders, the shoes and a drum. Then I thought the master might not be so hot so I tried to take it off the car to rebuild it....which was much harder than I thought. It probably took me about 8 hours to get it off of there and I've probably spent the same trying to get it back on. The issue is I cannot get the pedals back through the holes in the floor and on the mc at the same time.

If I put both pedals on the mc, the tops of the pedal arms hit the top part of the hole. If I put both pedals through the holes first and then try to get them on the mc, the angle is too extreme for them to fit. This must be doable, do I need to remove the floor?

I believe whoever restored the car replaced the floor there and riveted it down. He also glued the carpet to it so I can't see underneath unless I rip it up.

Perhaps are the holes in the floor cut smaller than the originals? Am I missing something? Can I remove the pegs the pedal arms mount to on the mc?

Any help would be appreciated.


#2 busycoupe


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Posted 04 January 2012 - 07:41 PM

Removing and installing the master cylinder is a piece of cake if you remove the floor section. When I bought my car the master cylinder was bad also. The previous owner had riveted the floor section in place and I tried to remove the master cylinder from under the car. After struggling with it for more than an hour i drilled out the rivets and removed the floor. With the floor out of the way the cylinder comes out in minutes. Reassembly is also easy, you assemble the pedals with the master before you bolt it to the frame.

#3 james curl

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Posted 05 January 2012 - 08:07 AM

My first attempt was to remove and replace from under the car, which is too much time and work so that I did not have to remove the original rubber floor mat. The second time the old brittle rubber floor mat went into the garbage can and the floor came out in about ten minutes and the master cylinder with pedals was a breeze to remove and replace.

#4 MattWalker


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Posted 08 January 2012 - 07:59 PM

And I got the master cylinder back on and all is great! Taking the floor out took like 20 minutes. Thanks for the help.

One more thing though, I have a spring in my hand and I don't know what it goes to. One end was in a small hole in the frame in front of the mc and is attached to a an egg shaped washer with two holes, one for the spring and one for a bolt? Does this go on the clutch pedal linkage as a return spring? Or possibly on the brake pedal as a return spring?



#5 Ralph D25cpe

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Posted 08 January 2012 - 09:11 PM

Sounds like the spring in the exploded view, spring 5-34-1 and clip
Attached File  exploded view master cylinder.jpg   116.29KB   88 downloads

#6 MattWalker


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Posted 17 January 2012 - 07:04 PM

Thanks alot. This forum is amazing. Thanks for the help.



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Posted 17 January 2012 - 07:11 PM

Yep it sure is! I only wish it was around 10 years ago when most of this stuff I had to figure out myself. My thanks to all the people here that have helped all the other none knowledgeable people out with there particular problems.:)

#8 Goodlet



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Posted 01 April 2016 - 12:39 AM

after sending my P15 to a brake shop,for a master cylinder and drum  rebuild ,My brakes have locked on (needing a tow home) 


i have not the confidence that they can (or want) to fix the problem.so i want to do this my self.


the problem (I think) is the relief valve which keeps fluid  in the pipes etc when the pedal is released.


The instruction book says that this is a simple job to fix (you adjust three phases of the pedal travel numbered A loose , B take up C Action, I have done this but no luck. the manual says that the relief port should squirt fluid but it only does this when the other measurement are wrong and still the brakesxare locked solid. 

Edited by Goodlet, 02 April 2016 - 12:21 AM.

Also tagged with one or more of these keywords: brakes, floor boards, master cylinder, p-15

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