Master Cylinder Rebuild

Over the last couple of months I have noticed the brake pedal is getting mushy.  The brakes have been bled and adjusted so I am thinking the master cylinder needs a rebuild.  After all it has been 13 years since the last time.  Or so I thought.  So when we had a 50 degree day in December I figured it was time to get to it.  The only real problem is it is raining outside so I have to work in my very cluttered garage.  This will be fun.

You can see that the master cylinder was leaking at some point and the Hill Holder is leaking now.   This looks worse than it is.   The leak is tiny and I have no real way to fix it without tearing the Hill Holder apart again.  I should have looked at this page before I started because I would have realized it actually has only been two years since the last rebuild.  Sometimes I am an idiot.

But I only figured that out after the fact.  At the time I at least got the master cylinder out without major trauma.

First step is to remove the Hill Holder.  I have this technique down.

Done.  I am working in a container to keep the mess down.

First mess of the day.   Taking the master cylinder apart I did not make sure it was empty first.  Whups.   This is about to become the theme of the day.


Again I have this down to a science.

Here are the old parts from the master cylinder.  They looked pretty good, which should have got my attention.  There is some crap in the rear seal on the piston.

Bore looks good!

I did see this though.  This is the machined sealing surface where the hill older mounts.  I missed this before.  There is some damage or bad machining here.

I used a flat surface and some 240 grit sandpaper to dress the surface.  It looks a lot better.  Once I got the worst of the damage off I used 400 grit to clean it up.  Then I cleaned everything out.

New parts getting a bath in clean brake fluid

And assembled.

I put the Hill Holder on with new copper washers.  I also put plugs in all the outlets except one.

I then bench-bled the master cylinder.

Ready to go back in.

Installing the master cylinder I managed to pour a lot of brake fluid down my arm and on the floor.  But I got it back in there.  Then I started bleeding the brakes.  And bleeding.  And bleeding.  I cannot get the pedal to firm up.  To make matters worse I kept making messes.  Spilling brake fluid, hoses coming off the bleed nipples, dropping stuff.  Very frustrating.  Eventually I ran out of brake fluid and time and gave up.   Then the temperature plummeted to the the low single digits so no further progress.  All in all this has been a sterling example of how NOT to troubleshoot and fix a problem.


Master Cylinder Rebuild — 1 Comment

  1. My 41 will be race only, like it ran back in the mid 60’s. So everything in the drive train it high performence…I am looking for the Studebaker and Champion emblems that go on the side of the hood. Thanks nice car…Ted

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