MGB - master cylinders (Part 3)

Today, we finish up the master cylinders in the MGB. In Part 1, we removed the old ones, complete with the pedal box and pedals. In Part 2, I covered disassembly, parts and re-assembly. Today, we'll get everything back together again. When we left off, the pedal box was put back together with the brake booster on one end and the clutch master cylinder (MC) on the other. The box is hovering over the hole in the engine bay where the pedals dangle into the driver footwell.

Box Seal

wrestling in the pedal box

Once the pedals were over the hole, I loosened the clutch pedal pivot bolt and pulled it partway out, testing for enough play to fit the pedals through the hole as I did. Once the pedals made it through, I pushed the bolt back into place and tightened it down. With some twisting, (and moving the heater hose out of the way), the box dropped into place.

Getting the box in-place is the hard part. Of course, I got my box as far as I described above and then realized that I hadn't gotten my bottom seal in. To get it in, I sent it from below, stretching it around the pedals and then fiddling with it to get it in the right spot to seal. Frankly, I think I was sent the wrong seal (it is square, the hole is not), but it will work well enough.

Bolting the Banjo

brake calipers - before

While you still have freedom of movement, pull the shipping plug from the clutch MC and attach the banjo bolt. If your new clutch MC was like mine, it did not come with a new banjo bolt, fitting or copper washers. You'll need to re-use your old ones. The banjo bolt and fitting clean up with steel wool. Be sure to get all the little steelie bits out/off before you install. I used brake cleaner after polishing. Also, the copper washers need to be annealed for them to make a good seal. To do that, you need to get them red hot: hold with needle-nose pliers and torch with a propane torch. Once cool, and the brake cleaner wiped and dried, assemble the banjo bolt, fitting and copper washers into the rear of the master cylinder. Tighten down with a 1/2". Unlike the banjo bolt nightmare I had with the steering rack on the Jetta, this was cake.

Wrap the end of the clutch hard-line with plumbers tape and thread it into the fitting. Tighten with a brake flare wrench. I was able to use my 12mm from my VW tools.

Box Final Install
Now, you can attach the pedal box to the car. I started by lining up the holes I could see from above, and loosely threading the bolts in, then moving inside the car (on my back) to get the three from the driver foot-well. Last, I did the 2 that thread in from behind the dashboard. Times like these serve as a great reminder to loosely thread in ALL of the bolts before you tighten any. I, of course, continue to need to learn that, so I had to loosen many bolts in order to get those last two in. Then, tighten them all down.

Last, loop the return springs around their respective holes in the pedal shaft and connect the other end to the underside of the dashboard. I've found that the pedals rebound well without these, but I'm sure the engineers wouldn't have put them in if they weren't necessary... so... I put them back.

Finish Clutch Master Cylinder

clutch MC is hard to reach

Box in? check. Pedals tight? check. Clutch MC plumbed? check. Next, we finish off the clutch master cylinder with DOT4 brake fluid. This sounds simple enough: put fluid in the metal can. Because of it's location up against the firewall, nearest the left-side bonnet hinge, getting a jug or even a really tiny bottle, of brake fluid in a place to pour it is virtually impossible. I imagine the bigger shops, or a place where you have a couple extra pairs of hands and some safe part storage, the bonnet is pulled waaay earlier, so it's not as big of a hassle. No matter. We're inventive. I dug through my old bio-diesel stuff and found a 10ml plastic syringe. With is, I was able to draw fluid from the bottle and add to the metal can without getting a single drop anywhere else.

If you use the syringe on a new master cylinder, expect to add at least 40ml. I filled until I could see the top of the fluid near the lip. Then, I put the cap back on, pumped the clutch pedal like mad and repeated. At one point, I figured out that I could move the master cylinder with a spanner through the top of the pedal box, so I didn't need to move around to get the MC primed. After about 5 syringes, the MC started to give good resistance. I moved to the cabin and worked the pedal with my foot, noting that the car moved in and out of gear with the pedal movement. I topped off the fluid, and called it good. A driveway test drive should shake any little bubbles free.

Prepare Brakes

VHT paint drying

Some like painted calipers. Some don't. Since yucky stuff gets onto surfaces, and looks worse when the yuck is on top of something light colored (like battleship gray unpainted steel calipers), I prefer black. Since I had the calipers off to do the front end rebuild (see parts 1, 2, 3 and 4 if you haven't already), they were ready for paint with very little extra work. For anyone else, you need to remove the calipers, disconnect the brake lines, etc. To me, that's just too much work unless you were in there to do a brake job anyway. I pulled the flexible brake line and pads, taped off the bleeder, plugged the brake line hole and scrubbed them with steel wool. The PO had shot them with some red paint that didn't adhere too well, so that needed to have an edge for the new paint to grip. Feeling the difference on the painted versus unpainted was interesting: the unpainted had a grain that gunk was attaching to where the painted side didn't. As a result, the paint, while not too good, still kept junk from caking on there. Food for thought. Anyway, after they were scrubbed, I blew them out with compressed air and them sprayed them down with brake cleaner to get any little bits of steel wool dust off. After they dried, I wiped them down with some mineral spirits, suspended them with bailing wire and shot them with VHT (very high temperature) flat black paint. They fully cure at 200*, but the off-gassing that happens when you bake-cure makes an oven unusable for anything else again. So, I decided I would let them cure through use. I'll just have to remember that they will smell a little bit the first time I drive on them, so I don't freak out.

Sew it Up
Once dry, pull the tape and brake line plug, re-assemble the pads and retainer bits. Thread the flexible brake hose back in, and install the calipers back onto their respective swivels. If you can't remember which is which, consider that the brake bleeder bolt should point up (so the air bubbles can work their way out). Thread the flexible hose into the hard lines and check your wheel movement isn't compromised by the brake lines. I've never had this be an issue, but my experience is limited compared to others, so maybe this is a thing. I figure it's always better to be careful and have all of your surprises be pleasant ones.

a little scrubbing goes a long way

There are a few little mop-up things to do. The pedal box cover needs to be put back on. This takes 1/2" #6 sheet metal screws. I recommend replacing the seal that sits beneath, if yours is original. Or missing. Bleed the brakes with the MityVac. Verify the hand brake works. And last, give it a test drive. I haven't gotten to that last part yet, since I still need to get the fuel tank in. Oh, and I need to do something with the cooling system. I'll get to those here shortly, and post soon after that. I know I'm running against time, if I want to get a drive in before the weather changes to solid rain as it does here in the fall. We usually have until right around Columbus Day, but the clouds we've seen lately lead me to believe that the weather will shift early this year. We'll see.

As always, thanks for following along.