Saturday, May 29, 2021

Brakes I

Now that the clutch is sorted, the next big job is being able to stop what can go.  So, brakes!

Rebuilding master cylinders (brake and clutch – I did that one too) isn’t difficult if the parts you start with are in good shape.  However, if the bores are damaged in any way, toss it and buy a new or rebuilt unit.  Brakes are safety items, so don’t mess around.  But a good core will yield a good result and be as good (and safe) as new.

I started with the master cylinder, which was not doing anything other than being a lump.  Removal was pretty easy - I've been having good luck with taking things apart on this car.  The lines came off easily and the master unbolted from the booster with little drama (other than having to take the intake off that I had just put back on).

The first step was to remove the reservoir, which was actually the hardest part.  The screws that hold it in place were very stubborn, but enough penetrant and a large screwdriver-with-visegrip-handle made it happen.


The next step is removing the primary port adapter and secondary port seal, to get to the insides.

Then it's a pretty simple job to remove the pistons, starting with removing the circlip that holds them in place, then extracting the primary and its spring, followed by the secondary and its spring.  The secondary is held in place with a little pin, which is removed by compressing the piston/spring using a long 'soft metal rod' (long 3/8" extension) and pulling out the pin.

The last part to remove is the pressure differential assembly.  Okay, so I fibbed a bit before - this was the hardest thing to remove, though those screws were knuckle-biting.  Anyhow, this is done by first removing the plug that holds the pin in place.  That took a long 1/2" breaker bar and steady pressure while clamped in my trusty vise.

Now the real fun begins.  The manual states to remove the pin with air pressure, but guess what wasn't moving.  I did finally coax it into a bit of movement after soaking in penetrant, and then I was actually able to pop it out with air pressure as recommended.  But it was a hard battle for a while, because I was afraid to bend or break things.  It turns out this was an abundance of caution, and the bore was intact.  Here's a couple of pics of the pin centered, and then moved... then the little bastard itself.

Once apart, inspection showed that the bores were all clean and undamaged, so my trusty rebuild kit was going to get put to good use.

But first, a thorough clean and rubber replacement!

As the Haynes manual says, "assembly is the reverse of disassembly."  So in went the differential pin and cap, followed by the secondary spring and piston, and that little pin I mentioned before.

Next in is the primary spring and piston, held in place with the circlip, with everything lubricated before assembly of course.

Finishing the job is to simply replace the primary port adapter, fit the new seals into the bottom of the reservoir and attach it to the body.  Top it off with a new vacuum seal and cover on the front, and it's complete.

I don't have a pressure differential switch, as it's make of unobtainium for 1975 (only).  The later switches are apparently constructed a little differently, though I cannot see how.  I may buy one anyhow to try out, or keep hunting unicorns.  The switch is mechanical and not fluid-activated, and all it’s going to do is light the light on the dash – but by the time the light goes on, you’ll be looking for the grab handle and checking the glovebox for a clean pair of undershorts.  So I may just plug it to keep the weather out like so many people do.  A properly bled system won’t have issues.

Refitting to the car is simple, and took less time than removal.

And there you have it.  Next job is rebuilding the calipers, which ought to be fun.

No comments:

Post a Comment