cruiser
Well-Known Member
Good evening A body faithful. Thirsty for another sleep inducing chapter in our component restoration journey? Well, you're in luck tonight because I've got just the ticket for you. This one is a bit different however, as this project is an upgrade instead of a component restoration - so here we go. My 1974 Gold Duster came from the factory with the B41 power disc brake option. With the lightweight slant six up front, this is an excellent braking setup for my car. As we all know however, just about every Mopar vehicle back in the day suffered from a leaking brake master cylinder. My Duster had the characteristic paint damage to the firewall and left front subframe from leaked brake fluid. This corrosive oil rusted the master cylinder and pretty much anything else that it came into contact with. I tried everything to stop my leak. New lid gasket, no help. Tighten the cover bail wire, no help. File down the mounting surface on the master cylinder, no help. Professionally rebuild the master cylinder, no help. Finally, I was just plain fed up with the endless problems of these units, and with the ever present puddle of brake fluid on my garage floor. I'm all for keeping my Duster as stock and original as possible, but I just couldn't deal with the trouble of this setup any more. I decided to do the unthinkable (for me) and upgrade to a Dr. Diff aluminum master cylinder. The new MC came with an adapter plate for my four bolt vacuum booster, but no installation directions. My FSM was a big help, so step one was to remove the existing rusty MC. When I did, I discovered that someone had previously removed and reinstalled it with the two piece plastic/aluminum spacer upside down. The second from last photo below shows the incorrectly mounted upside down spacer. The aluminum portion of the spacer was badly corroded from brake fluid, and the black plastic portion of the spacer was broken and partially crushed. I found a very nice replacement spacer set, and bead blasted the aluminum portion revealing its original natural metal finish (see before and after photos of this spacer in its correct vertical orientation). I then painted the spacer with four coats of Krylon Clear Chalky finish, and treated the plastic portion to plastic restorer fluid after cleaning it up. I then fabricated a new foam filter and installed it onto the spacer set. (I'll bet you didn't know that the power brake booster had a filter in the spacer). I assembled everything then installed the spacer set onto the vacuum booster studs. I then attempted to adjust the length of the MC pushrod for the new MC but broke the tip off in doing so. I salvaged the tip off a used pushrod and installed it onto my original rod, then installed it into the MC. The length of this pushrod must be adjusted before installation to make sure the brakes work properly. I didn't have a pushrod depth gauge, so I fabricated one from the shaft of a Q-Tip and used this to set the depth of the rod tip. Finally, I installed the new Dr. Diff unit onto the vacuum booster after bench bleeding it. Brake line attachment went well, and I then bled the entire system and refilled it with Valvoline DOT-3/4 brake fluid. Careful road testing followed, and everything worked perfectly. My finishing touch was to attach my Duster's original aluminum MC part tag to the outboard mounting bolt of the new unit. I did this to keep at least part of my original MC with the new unit. This tag has the last four digits of the original MC part number stamped on it, along with the word "PWR". Kinda cool, I think (see photos). And what of the original MC? As the photos show, the original was pretty ratty but I kept it of course. I bead blasted it then refinished it in Krylon Fusion Satin Black and off it went into long term storage. Like you guys, I like to hang onto the original parts from my car. So I now have my leak free braking system and no more garage puddles. Sleepy yet? Go get yourself a bedtime snack and head upstairs for a nice long relaxing nap - which is the entire point of my series. Night night!
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