Beck TD, Part 24: Remote Brake Fluid Reservoir

This is another one of those projects that has been proceeding in fits and starts for several months. In 1952, MG chose a really dumb method for maintaining the brake fluid. The master cylinder is under the floor, and you check the fluid level by removing the carpet, then a drop-in panel, then use a 13/16" wrench (same size as the spark plugs) to remove a threaded cap, and then somehow get your head under there with a bright light to check, and if needed, top up the fluid without spilling it in the interior of the car. Dumb!

I'm not the first to think this, and adding a remote reservoir for the fluid is a common modification. In fact, a guy in Germany named Declan Burns sells all the parts to do it, and it makes a lot of sense to use his tried and tested parts. He doesn't seem to have an Internet storefront, but he's easy to find on the MG Experience forum, and is very responsive to emails in English. https://www.mgexp.com/

But a big part of the fun of the car hobby for me is to make my own custom parts, so I elected to do it myself. The two ways that are usually used are to either go through the filler cap, or through the plug on the back of the master cylinder. I elected to go through the cap, and via some research determined that it was 1-1/8", 20 TPI in British Cycle thread form. That is gibberish for most folks, and pretty daunting for me - I decided to enlist Phil Oles' help. 

British Cycle is a 60 degree thread, just like good old American UNC and UNF. Phil and I made a large nut to use in testing, and then a large bolt in the matching thread, using a standard UNC/F threading tool. Those parts worked together, but the bolt wouldn't thread into the master cylinder more than about one turn. More research showed that British Cycle is more rounded than UNC, so the bolt was probably binding in the threads. To get that right, we would need a custom-ground threading tool. Back to the drawing board.

In the course of all this, I determined my old master cylinder was leaking, so I bought a brand new one, pictured above. That gave me a spare threaded cap to play with! Phil came over again, and we started experimenting. The cap (new one pictured) has the big nut on top, and on the underside a vent arrangement:

To remove the vent, I drilled successively larger holes until it was almost gone, and pried the rest out. What was left was a reservoir with a depression in the center:

I cleaned up the depression with a 1/2" end mill, and then used a boring bar to make the sides of the reservoir perfectly round. Once that was done, I could make a brass filler plug to fit in the holes:

We left the workpiece right on the lathe, and used JB Weld to affix the cap to the plug. The tailstock drill chuck was used as a press to hold it tight together for 24 hours.

Once it was dry, I needed to ready the cap to receive a banjo fitting and bolt - not a musical instrument, but a special fitting that allows fluids to be transferred. There's a Wikipedia page here if you want to know more. That Lockheed script was cool, but I needed a flat surface for the banjo. I also needed that 13/16" nut to be about half as tall for clearance:

In retrospect, I should have drilled the cap all the way through in the first place. My brass fitting didn't seat fully in the depression, and I had to make a small filler to get the seamless result above.

I drilled and tapped for my banjo, and the test fitting went well:

Now it was time to get it to fit in the car. I had bought a Wilwood remote brake fluid reservoir, which came with the needed 1/4" rubber hose. I installed it on the master cylinder, and then spent a couple of hours experimenting with hose routings and custom hold-downs to ensure the hose wouldn't contact any moving parts or anything hot. No pictures of that, but I will report it was a real pain in the neck due to limited clearance.

I elected to mount the reservoir low on the front cowl, where I would see it every time I check the oil. It's held in place with self-tapping screws, and limited clearance made my right-angle drill a necessity to mount it.

No leaks in the initial testing, but I'm leaving it overnight to be sure. Then I'll bleed the brakes to make sure the fluid level does what I expect. 

I'm glad to get this done, since I'm installing carpet right now, and the last thing I want to do is get brake fluid on a brand new carpet! It will also help me sleep better at night to look at that fluid level just about every time I drive the car. With the old setup, I'd be lucky to remember to do it once a year. And when I complete the disc brake conversion with Cor's help, having this remote reservoir will make the final bleeding of the brakes much easier and more convenient. A good result!

Continue on to Part 25...