Changing master cylinder - need a little help

[mmcgough]

I bought a master cylinder and am in the process of changing it out but am stuck. I have searched the forum for info and have looked in the chevy assembly manual and cant find what I need. I cant figure out how to get the old one off. I am sure that this is just a dumb question but ...

I know that the 2 bolts hold it on, I know how to get the plunger undone, but the big holes on the top left in the picture below -- I cant figure out how to get them out from the ones on the truck. I guess they are the pivot point for the brake pedal - I cant figure out how that comes out. Any help would be appreciated.

Mike

[tmoble]

on the other side of the M/C from the pic you'll notice a small plate with a small bolt. take that bolt out, the plate will fall off unless the gunk is really thick. that little plate retains the big pin that the pedal assembly pivots on. There's usually a grease Zerk on the end of the pin. it's not tapered, drive it out from either side that's convenient.

You'll notice there's a bolt at the bottom of the pedal arm, take this bolt out to disconnect the M/C plunger from the pedal. Don't lose that bolt, it has an eccentric that serves to adjust the pedal. Might want to note which way the eccentric is pointed.

[mmcgough]

Thanks that helps a lot. The guns is super thick and there is a bunch of rust on it so i will have to clean it real well to get everything to come apart.

[agnes the dog]

If you haven't gotten it out yet, it might take some persuasion from a hammer + a similar sized socket. I had to whack mine pretty hard to get it out since it hadn't been greased in a LOOOONG time.

[OrrieG]

The shaft pin is good hard stainless, use a punch or old socket to keep from spreading the ends.

[mmcgough]

I have to say, that this is a lot more difficult than I thought it was going to be. I guess I am just not used to working on 60 year old vehicles. I first threw some gunk on everything and let it sit for a couple of days and then cleaned it off and now I can at least see what I am working with . I have most everything off but the pin just wont budge. I guess I will need to get a little more persuasive. I am thinking of going with disk brakes up front eventually, will this new master cylinder even work for that? or will i need one of the big ones that mounts on the firewall? I am hoping I can just have this one work.

[OrrieG]

Stock MC will not work with discs. Protect the shaft and try turning with vice grip or small pipe wrench.

[tmoble]

I ran a truck with Camaro front stub and disc along with stock drums on whatever axle I was running from 1993 to 2013. No problem with the M/C. 2013 I installed a 88 Vette rear axle assy, stock discs on it, still running the stock 57 M/C. No RPV valves, no combo valve, no nothing. just a T, lines to the front and back. Truck has seriously good brakes.

Of course, vendors hate this kind of stuff, nothing in it for them.

[tmoble]

Mike, you can unbolt (un-nut?) the brake pedal from the top of the M/C arm, get it off the truck, work on it on a bench. have you looked at the other side, see if there's anything holding it?

When you take off the block at the end where the lines come out, be careful to not lose the copper seal rings. I did that once and a hard time to find new ones. SHould have been new ones in the box, but no joy. PITA

[mmcgough]

Thanks for the input. I am going to get back under there and see what I can do. I will post an update once I get it out.

[mmcgough]

I know it has been a long time, but I finally got everything done. Brakes work great. I had to take an air hammer to get things loosened up, they were really stuck. Everything has been restored to new condition.

The only question I have now, is the following.

Is there a brake switch? What tells the brake light to light up? I have looked at the wiring diagram in the factory assembly manual and cant figure it out. I have to be missing something.

Mike

[Race.it]

If it's a pre 1955 I.e ad truck then the brake light switch is at the bottom of the bulkhead in the engine bay, just below where the column comes out. It's a leaver that activated the switch (which has a long leaver on it that contacts with the brake pedal arm.)

[mmcgough]

I found it. Turns out the previous owner decided I didn't need the lever. I now have a new one and will have brake lights soon

[Race.it]

So overrated these brake lights, with my truck had the switch, had the leaver no lights, so thought leaver was bust, nope it had had bodgy wiring and somebody forgot that for switch to work it needs to be connected not just at switch but other end also so that made my decision for a re wire.