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© 1999 Brian F. Schreurs
Even we have a disclaimer.

A failing brake system falls into the latter category.

The brakes on Col. Mosby, the resident 1974 Dodge 100 pickup, gave up their last just as it rolled into the garage to be serviced. We had to stop it with the trans. Ouch. Final diagnosis: new master cylinder and power brake booster. We bought the combination unit from Cardone (part #A1B-50-3716 at our local parts store) to make our lives easier. It's called a "loaded" booster. We also bought two quarts of brake fluid to flush the system.

First step, get the truck into the garage safely, preferably without crashing into the shelves.

The old master cylinder and brake booster, with the fluid sucked out.

Now locate the master cylinder... okay, we'll wait. Heh. Ready? Pop the cover off, and if there's any fluid left, use a brake baster (located in the turkey baster section of the local Grocery Racer's Supply) to suck it out and into a jar. Preferably a jar you never want to use again, ever.

With the master cylinder empty, disconnect the brake lines. These have 9/16" fittings; use a line wrench if you possibly can. When disconnected, plug them. If you don't have a plug, tape over the ends like we did. Real scientific, but the goal here is mostly to keep fluid from drooling over everything.

With the lines out of the way, the master cylinder can come off the power brake booster. It's held there by four 1/2" nuts. However (and this is to catch all you guys who don't read the instructions all the way through before starting), there is no need to remove the master cylinder. Never mind the service manual. Leave it alone.

Disconnect the vacuum line to the booster.

This is the brake booster from the brake pedal's point of view.

Now crawl into the truck, under the dashboard. The booster has to be disconnected from the pedal and removed from the firewall. The pedal is connected with one really big bolt -- the bolt head is 3/4" and the nut is 11/16". We grabbed the bolt with a ratchet and the nut with a combo wrench; doing this, you can take the nut off with a combination wrench while using the ratcheting of the socket wrench to keep from having to reposition the combo wrench all the time. It's easier to do than explain. Just try it and trust us.

The booster itself is held in place with four studs. The 9/16" nuts are accessible right there where you're already at to do the brake pedal. Three of them are easy; the fourth is going to take a U-joint and an extension bar. Have fun. Don't worry, the booster won't fall out with the nuts removed. It'll just sit there.

With the four nuts removed, go to your chiropractor. When you get back, go under the hood and give the booster a solid yank. It'll pull out, although the original boot might not want to go with it. Just yank it till the boot lets go, or rips off, whichever. You don't need it anyway.

If it does rip off, retrieve it. Also, the booster should leave a gasket stuck to the firewall on the engine side. Leave that alone. The new booster doesn't come with a new gasket.

The hole in the wall where the booster used to be. That brown mess is a gasket, allegedly.

Take the new booster and jam it into place. If you bought the right one, it'll fit with no problems. And it'll sit there, waiting for you to crawl under the dashboard again. Which is the next step.

That's right, get under there and bolt up the booster, then reattach the brake pedal. Topside, go reattach the vacuum line.

Fill the master cylinder. If you're going to wuss out and not bleed the entire system, bench bleed the master cylinder. We're not going to tell you how, because you're a wuss if you do. If you're working on a 1974 pickup, trust us, you need to flush the whole system. So go ahead and reattach the brake lines now.

Now it's time to bleed the brakes. Start with the right-rear wheel. Be sure to support the truck with a jackstand and take the wheel off.

With the wheel off, take this opportunity to inspect the brakes. Pull the drum off -- if you can -- and have a look around. Spray it down if it's filthy, which it probably is. Check for damage. Make a note of anything that might need to be serviced later.

Note to self: rebuild rear brakes.

Our shiny new master cylinder/brake booster, which looks mighty out of place in that engine bay.

Put the drum back on and continue with the bleeding. On the rear drums, the bleeder screw is on the back of the brake, just above the hydraulic line. It's 5/16". It might be plugged; this is easy to tell when you open it and nothing happens. If so, use a pick to unplug it. One of ours was actually plugged at the other end; we have to remove it completely to make it serviceable.

Get your brake bleeding kit, or your soda bottle with hose (whichever you have), and stick it on the end of the bleeder. It should be a tight fit.

Tell an assistant to push down on the brake pedal. Open the bleeder with a wrench (preferably a line wrench). Watch all the disgusting crap ooze out along with a bunch of air bubbles. Ewwww. When the flow slows, close the bleeder. Tell your assistant to let up off the brake.

Then tell them to push down again, and open the bleeder, and watch it ooze out, and close the bleeder, and tell them to let up. Keep doing this until, when stuff is oozing, it looks like new fluid instead of scary old stuff, and there's no air.

After doing a wheel, go check the master cylinder and top it off. If the master cylinder goes dry, you get to start over. Then put the wheel back on and move to the left-rear wheel. It's the same thing over there.

Next, do the right-front wheel. Our truck has disc brakes on the front. The bleeder is located smack on the top of the caliper -- easy. It's 3/8". The procedure is the same.

Finally, do the left-front wheel. With that, the system is bled. And, with the system bled, check the master cylinder level one more time. Then go test the brakes, coz you're done!

It looks really funny to see the nice shiny new parts in the old crusty engine bay. But it wasn't funny at all the way the brakes used to behave. Now they work better than ever. How much better does the new master cylinder/brake booster work? Well, imagine the difference between the truck stopping when you hit the pedal, and, uhmmmm, it not stopping. That's the improvement. And it's a darn good one if you ask us.