The LSSB 927 is a Girling/Lockheed repair kit for the GMC 159 that contains a replacement bearing (actually more a thick washer) and spring.  Also, there are small nylon trap valves under the brake line outlet adapters, so avoid using heat at that end of the MC casting.  Don’t ask how I know.....

OKmini.  I broke the link that connects the primary and secondary pistons in the disassembly of my MC.  Any chance that you were able to salvage one from the MC that you cut in half and is it available?

The connector and spring are needed. 

Connector??  Uh oh, mine is broken.  Am I screwed or would I be able to replace it using a couple of twists of .032 stainless lockwire?  If so, any idea how long the connector should be?

Are the pistons no longer connected? To actually change the seals, I drift the tiny roll pin out that goes through the connector. To successfully rebuild these it has to be complete. 

I used to soak the casting in phosphoric acid prior to a light hone inside and several coats of clear. Rick’s molasses bath process is similar. 

Per Mur’s advice, I used three days’ worth of PB blaster, a drift and a hammer and then inverted the master cylinder and slammed it on the vice.  The washer popped out.  Same for the secondary piston.  I found a ‘brake master cylinder snap ring plier’ on line that has jaws long enough to install the deeper snap ring. Fingers crossed.

48 minutes. Two notes: a surgical clamp is best for the deep circlip, and I used an impact socket held tight to the flange of the MC, and then hammered these onto the back anvil portion of the vice drifted the bearing out.

I appear to be unable to load images from the various apple devices I have here, if you care to email me I can send photos.

I’m in the shop where I have a couple of these units. One was partly disassembled and had come in one group of parts while another just arrived from an old friend.

the partly disassembled item has the bearing removed, and after knocking the loose washer out, I found the push piston assembly broken.

I then took a large valve spring compressor and removed the Spirolox ring from the complete unit. The ring broke..

I then added PB Blaster and heat.

After letting it cool, I took the drift I use to decouple rod change shifters and tapped the circumference of the bearing. I then spread the vice jaws and inverted the MC, and tapped it a few times, then I took a hammer and walloped the top. Once again upside down in the vice, I took the drift to the bearing and tapped, this time I was able to see it move. I added more PB Blaster.

edited to once more add the word Spirolox, which I had typed in twice. Hey loser spellcheck program: Spirolox Spirolox Spirolox

I think mur's response was meant to be tongue in cheek.  In any case, the only thing holding the bearing in is several decades of dissimilar metals seated next to each other.  My less than elegant solution ended up being to cut my spare MC in half and tap the bearing out from the other side. 

I actually thought about my marginally funny answer for a bit. These are really hard to get out. I sorted out my way of doing these alone, long before there was an Internet where decent answers are a moment away. It is a process that I arrived at after a lot of hard work, using practices based on lots of previous hard tasks on other slightly less difficult parts. I destroyed one casting before I figured out how to pound the bearing out on two anvils via the mounting ears.

If you get the MC fully apart and rebuild it, reassembly sees that bearing drop into place like it is no big deal. It seems almost unfair.

Mur-Thanks for your thoughtful, considerate and sincere reply to my question.  Very much appreciated.  Two thumbs up.

I did mine and i didnt remove the brass thing, because you need to remove the tiny needle across in order to release the spring to easily slide the new rubber seal.  
Well i managed to slide the rubber seal without damaging it, i used a little bit of motor oil (not brake fluid) to lubricate it, and yes the rubber seal can stretch up to 3/4 of an inch . 

Experience taught me, not the book of haynes.

Spite?

Mur- I’ve run into the same problem as the other gentleman. I can’t get that brass bearing out.  What actually holds it into the master cylinder casting?

1976 cars are awesome-especially the illuminated rocker switches! Last of the hard mount subframes, the safety doors, finished rain gutters, etc. 

Good luck with your next MC dismantling. There is great value in leaving the penetrating oil to soak a long time. Heating things up a couple of times is also a good plan.

When you have it all apart, you will see that the reservoir needs to be filed flat to seal against the casting, they warp. After filing you may need to file down the spacer rings on the bolts that hold the reservoir on.

Thanks mur.  I had tried that but this has been off the road since 1983 so much is seized.  I ended up removing it by drilling many holes and pulling with a slide hammer.  Destroyed of course.  I was hoping that the spare on the parts car may be able to donate a nylon version but from what you say it is likely brass as well.  I'll have to take more care with that one....

I have done many of these, I have only seen one nylon bearing.

I thoroughly soak in penetrating oil, tap the circumference of the bearing with a suitable drift to loosen the bearing, and then knock it out by inverting the MC and pounding the ears on a suitable pair of anvils.

Obviously, this is harder than most tasks, and the success of these rebuilds is not guaranteed. Good luck.

Hi All - I'm in the middle of rebuilding an early dual master cylinder (GMC159) and have run into an issue that I can't find any resources for.

After removing the spirolex ring, spring and circlip, all the manuals I have indicate that the next item to come out is a nylon guide bearing.  However, the bearing in my unit is clearly brass, and is pressed in extremely tight.  In an effort to remove it I have drilled 2 small holes on either side of the piston, tapped in a couple of screws and made a puller to span the piston so that I could use a bolt threaded through a piece of steel plate to withdraw the bearing.  Not budging and actually sheared the bolt.

 

Has anyone  run into these brass bushings in the past and can offer any tips on how to get it out?  I can’t get any deeper into the guts of the MC until I do.  This is a Canadian spec 1976 BTW.  Lots of weirdness on it.

 

Thanks,

 

Corey,

 

BC, Canada