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Q-talk 90 - Airheart Brake Fluid Leaks

I had a problem in the past with my brake master cylinders leaking all the time. I have the original Airheart master cylinders that were provided with the kit. They are both located on the left side, on top of the main tank and forward of the instrument panel. They are hand operated only and they have worked very well for me. The only problem was that both units were leaking so badly that I had to place a folded paper towel under the cylinders to prevent the brake fluid from leaking onto my seat cushions. I also had to continuously monitor the fluid level and refill one or both units two or three times a year.

The fix was an easy one. Originally, I had those solid plastic, 1/8 inch, pipe thread plugs in the top of the master cylinders where you add the fluid. I replaced the plugs with regular straight nylon fuel fittings. These are just standard nylon fuel fittings with a 1/8 pipe thread on one end and a 1/4 inch barbed fitting on the other. I attached a piece of 1/4 inch clear tubing to each fitting, ran the tubing straight up, behind the instrument panel and secured them. Each tube was about a foot long. This seems to have resolved the problem by venting the master cylinders and the length of tubing keeps the brake fluid from squirting out. When I yank real hard on the brake lever, I can get the fluid to jump up into the tubing an inch or so. You might be able to get away with a much shorter piece of tubing. If you had a common brake fluid reservoir plumbed to top of the master cylinders, it would accomplish the same thing. The fluid level now stays pretty consistent and I only check them during the annual condition inspection.

You can order a printed copy of Q-talk #90 by using the Q-talk Back Issue Order Page.