Wednesday, July 28, 2010

'67 Dodge Mahaul Master Cylinder Rebuild Beginning

My brother and I removed the master cylinder (MC) a month or so ago from the '67 and I finally started the rebuilding process this week. The master cylinder is a dual (split) system, with a separate system for front and rear brakes. My '66 has a single system, so if I had a loss of pressure, I would loose all my brakes excluding the parking brake.

I went to Larry at Prairie Grove Auto and he ordered a rebuild kit, Carquest part# brk M448, about $50. The chassis is a p375 and the MC piston diameter is 1.25".

I disassembled the MC and bead-blasted it, but I still need to hone it and paint the outside. One of the curses of the MC location in the Travcos is that it is under the floorboard in a dirty environment and hard to fill and even check the level. I have decided to design and install a remote reservoir for the master cylinder. Roughly copying best examples on the net, I have drawn a cover for the MC that will be tapped with two fittings, one over each OEM reservoir, made from 3/8" aluminium plate and bolted down onto a gasket. The fittings are connected to one hose each that will go up to a Mitsubishi Eclipse remote reservoir from one of my parts cars and mounted somewhere TBD, just above the MC to allow proper gravity flow. I have access to a CNC mill and will mill the cover early next week. I will also attach the low level switch in the Mitsubishi reservoir to an LED I will mount in the dash to warn of low fluid level, but even if it is empty, there should still be liquid in the OEM reservoir. I plan to use DOT4 fluid and hope to find speed bleeders to bleed the system often to mitigate water absorption. The MC failed as it had rust sludge and pitting in it, the result of moisture. BLEED YOUR SYSTEM OFTEN! (I need to follow my own advice BTW, LOL).

No pictures yet, sorry.

The '67 MC has a "flat" oval/rectangular cover that is held in place by a wire snap/clip. The '66 has a screw-on cap (cap has male threads) and I will be designing a remote unit for it after we complete repairs to the brakes on my brother's '67.


Charles said...

Change yours over to a dual braking system, in the interest of safety.

1966 Travco 270 said...

Yes, when I first got her I thought how crazy it was to have a single system. It just comes down to doing it and like anything else, exactly what path do I go down. Next upgrade, or go all the way? Where do you stop, disc brakes?

CompuMech said...

The remote reservoir is a great idea. I don't have access to a CNC machine and I don't trust the snap-on cover on my '81 Barth's brake MC to not leak, but I was thinking on adding an external reservoir that was at exactly the same height as the master cylinder. I could run a hose from the bottom of the external, easily-visible reservoir, into a tapped hole 3/4s of the way down the side of the MC. It would give me a good idea of the exact level, plus extra capacity. The downside is, if the new system leaks, I'd quickly lose most of the fluid. Your idea is pretty nice, in that any leaks you introduce aren't going to compromise your safety as much.

Great blog! I just discovered it. - Daniel.