Brake fluid on hangar floor

[vindio]

'47 C120

Every few flights (seems intermittent), we walk into the hanger to a small pool of red hydraulic fluid, right under the fitting that connects the right brake line to the fuselage (pictured).

The fittings on the picture felt tight, but I have torqued them down a little more. Looks to be dripping from the higher fitting (the one that actually makes contact with the fuselage).

Braking action seems fine, but worried that the system may run out of brake fluid.

Question: is refilling it something that a pilot/owner can do, or does it require an A&P (by regs, or by skill?).

Thanks!

v

[6643]

"Replenishing hydraulic fluid in the hydraulic reservoir" is one of the tasks listed as "preventive maintenance" and may be performed by the holder of a private pilot's certificate. See part 43 appendix A for the other 30 tasks you may also perform.

That said, you need to know how to perform the task, which is a more than "I think I can figure it out" and you should also know how to make a proper log book entry to record performance of the task.

That said, you should fix the leak first, and that does not fall under the definition of preventive maintenance. There is a hard line on the other end of that fitting, called a bulkhead fitting, and it could have a leak in the opposite fitting, or in the line itself. If the leak gets worse, or the reservoir runs low, you will loose braking on that wheel.

[vindio]

Thanks John ... we're going to follow your advice, and have an A&P look for the souce of the leak.

[6643]

If you remove the trim around the gear leg you may be able to see what's going on. Removing and replacing trim like that is also one of the things you can do.

[vindio]

So, we had the aircraft in the shop, and they "found nothing wrong" with the right brake and line (CLEVELAND brakes, btw).

They topped off the right brake fluid, but we are now noticing that the airplane pulls to the left severely, when braking after a wheel landing (at speed). Much less noticeable when taxing around (lower speed, obviously).

What do you guys think the next troubleshooting step should be? Bleed the line? (the shop did not do that).

Still bugs me a little, that "nothing was found", yet that fitting was clearly leaking at times.

Appreciate any insight!

v

[V529]

Step 1: Bleed the brakes. Both peddles should have the same amount of "feel" to you as the pilot as you press with your feet on the tops of the peddles. My guess is that there is air in the lines on the weak side.

Step 2: with a leak such as you have, a few more pictures, including 'not a close up' (it's difficult to get perspective when the picture is inches away, there should be a 3-5 foot back pic, then the close up follow up pic)will help us, help you. So.......step two is identify the leak.
A. The leak can be anywhere. For instance: The caliper can be leaking because the housing is old and fluid leaks past the puck seal. The caliper housing can be cracked where the AN fitting is threaded into the caliper. The fluid hard line under/beside the gear box bulkhead can be chafed on the steel structure(very common), or the master cylinder can be leaking.

Step 3. Your brake can have the same feel as the other side, but if the brake linings got contaminated by brake fluid the linning to disc adhesion will be significantly impaired. You need to clean off the brake fluid. (Iso alcohol spray, followed up with compressed air works great)

Step 4. If you have differential brake action/response, then you need to use differential peddle movement to make up for the lack of brakes on one side. (temporary until you get it fixed), in other words more rudder on the side with less brakes.

Question, will the right side "pump up". In other words do you get better brakes by double(or triple) pumping the right weak side? If yes, then air in the lines is the culprit.

Bleed the brakes, clean the fluid and look for leaks and report back. We're here to help.

[simonlowther]

Hi,

No expert here but just sharing from past experience. After bleeding your brakes which seems a good idea regardless check the little square stopper on the brake reservoir. It should have a little vent/hole in the top. Check this hole is not obstructed or gummed up.

Good luck
Si.

[edidin]

Not directly related to the leak per se, but when I had to fix specifically the right side brake on my 120, I found that the line from the master to the calipers had two bends in it due to the greater length from the master. On that side, I struggled to get all the air out by the usual pump and bleed from the bottom, or pressure from the bottom to the top. However, a cheap vacuum bleed(er) from the bottom solved all issues quickly. My theory, possibly nonsense, that the vacuum bleeding collapsed air bubbles that were lurking in the bends even as pressurized fluid went past them. Did have to buy the $30 Cleveland bleeder adapter, but that's handy to have anyhow.