Tuesday, September 5, 2017

MGB - master cylinders (Part 1)

Another post about the ongoing work on the MGB. Today's post covers the removal of the brake and clutch master cylinders. This got long, like so many of my posts these days, so I split it into two, with the follow-up post covering the re-assembly and re-install. It should be noted that sometimes I revert back to a sworn-at previous owner (SAPO) and start removing things without taking pictures. This is one of those times, so the pictures are from either the re-assembly or the internet. Sorry. Sometimes I suck too.

This is as logical a place to start as any. "After the list of other things that have been done why the (expletive) would you open up yet another system?" Yeah.. that's a really great question. It's not because I'm sadistic. You see, I started with the brakes. Long before I discovered the rust-thru on the floors, or learned about the front suspension having window insulation acting as bushings, I tried to fix the brakes. I completely redid them at the wheels. I even replaced the hoses with nice new ones, but I couldn't get the rear's to bleed. Turned out, the master cylinder wasn't pushing fluid to the rear, so it had to go. After some reading, I learned that for some weird flaw of nature the clutch master cylinder fails within 6 months of replacing the brake master cylinder if you don't replace them at the same time. Rather than tempt Murphy's Law, I figured I'd just get after it. Besides, winter was coming so the little car was going into the garage anyway.....

Remove the Brake Master Cylinder (MC)
my engine bay - before
After I tried all sorts of combinations of efforts to remove things, I figured out that it wasn't nearly as complicated as I (and the internets) was making it. First, remove the electrical bits: the pressure sensor and the brake-light switch. The first unplugs, the second unthreads. Then, remove the brake hard-lines from the master cylinder. There are three, two head to each of the front wheels and one heads for the rear. Put a small catch-pan under the master cylinder before you start opening these or you'll get brake fluid dripping all over the driver side of your engine bay. It is a really small space under there, so I used a washed out yogurt container as a catch-pan. I taped plastic on the brake line ends to keep some water out (and brake fluid in), but after the front end suspension work, the lines are completely clear. If you're just pulling one and slapping a new one in, It might be worth doing. I didn't see the downside except consuming 10 minutes of my time. Once the fluid lines are detached, remove the two nut/bolts which hold it to the brake booster. With a wiggle, it should come right out.

Remove Brake Booster?
not mine, but better angle
With the brake MC out of the way, the next in line is the brake booster. This unit takes vacuum from the engine and uses it to help you stop. Very clever. First thing to remove is the hose from the engine to the brake booster. If your rubber is as old as mine, make a note of replacing it. The booster is held onto what's called the pedal box from within the box, so before we can go any further, we need to pull the lid off the box. It is held on with a bunch of little fasteners. Depending on how much your car was messed with, these could be bolts or screws, Phillips head, slotted or hex. Or a combination. Mad love for prior owners. Someone will be cursing me this way one day. Anyway, remove the fasteners and the lid on top. Inside is the magic where the pedal action is translated into brake or clutch motion. In here, you can see how the brake pedal actuates a lever that runs forward into the brake booster and how the clutch pedal hinges on a pin connected to the clutch MC between the pedal box and the firewall. Whoa. So.. maybe this is why everyone says to replace the clutch MC at the same time as the brake. You have to get so deep anyway, you just might as well.

So, how do you get this thing out? You can try starting by removing the pin connecting the brake pedal to the lever. This is a royal PITA. You need inhuman fingers to do this. Same goes for the clutch pedal/MC and even getting the brake booster off. After the fact, I figured out that you don't need to separate the brake booster from the pedal box at this point. You can just remove the booster with box all at once. Whaaa???

Remove the Clutch Hydraulics and Pedal Box
thank you eBay for your blurry picture
Skipping over the brake booster, we move to the clutch master cylinder (MC). Disconnect the hydraulic line that runs along the firewall. Again, I wrapped it in plastic wrap and then taped it sealed. Now, the only thing that is holding the clutch master cylinder, the brake booster, and the pedals in the car are the little bolts which are holding the pedal box in. Many of them are addressed from the driver footwell. Only a couple (those on the engine-side of the box) are removed from above. They are different sizes, which is a little weird. Anyway, once the box is free, the entire unit can be coaxed out of the car.... but wait: the pedals are too wide to fit through the hole! Lift the box and pedals as a unit and once you have it up as high as it will go straight up, twist it counter-clockwise while you lift and you can get another inch or so. That little bit is enough for you to get access to the clutch pivot bolt. The bolthead is sticking out the left side of the box. 1/2" socket will remove it, and the pedal will be free enough for you to get the unit out. Seriously, it works. The pedal will dangle a little strangely, but the 2 pedals will fit out of the hole this way, even with brand new pads.

With the box on your bench, you can easily pull the various parts off. The brake booster is held on with 4 1/2" nuts, and the pin from the brake pedal is easier to get to when you're not leaning over a wing (fender). The clutch MC is held on with 2 1/2" bolts. One of them twists into a fixed nut, the other needs a wrench on the nut on the inside. Like the brake pin, the clutch pin is easier to get off at this point. I found needle-nose pliers to be up to the task.

Now, your pedal box, master cylinders, brake booster and pedals are all apart. In part 2, I'll cover cleaning, painting and re-assembly. Thanks, as always, for following along.