Check your brake fluid levels!

Confession time. Ignorance bit me in the butt (pretty typical), but nothing was bruised but my ego.

When the RV-1 was on the Barnstorming Tour of the Midwest, I landed at Toledo, OH, to meet Bob Mills and The One. Upon landing and rollout, I discovered that my tailwheel didn't lock. I had to use differential braking while taxiing to the ramp.

As I contemplated borrowing someone's hangar and tools to service the tailwheel, I jostled it a bit and the wheel locked OK. We took off, landed back home without incident and I reminded myself to service the tailwheel ASAP.

I had no issues for the next 10 hours or so. Tailwheel was locking perfectly, so I figured I'd just wait until condition inspection time and do it then. That is the moment when a little voice should start saying, "Stupid ... stupid ... stupid ..."

Last week, I took Smokey up for a local flight just for fun. Came back to land and, as the tailwheel came down, started an immediate departure of the runway to the right. I immediately knew that the tailwheel wasn't locking, so I pushed on the left brake to straighten out, but to no avail. I was no longer a pilot but a passenger.

I missed the runway lights, careened into the grass and came to a stop. The tailwheel locking pin was stuck again, but of more concern was that I had no brakes.

As I taxied to the hangar, I realized that I had brakes, but not much. Far more pedal resistance on the right than on the left.

I pulled the tailwheel and disassembled, cleaned, deburred and regreased it. Works like a charm now. However, checking the brakes was another story.

When I checked the brake pads last year, I still had significant pad thickness left, so decided that I'd change them this year. I pulled the left wheel pant and found that I still had decent brake pads. Hmmm... so, I pulled the baggage compartment floor to see how the brake fluid levels were (I have the kind with the master cylinders and reservoirs mounted to the brake pedals). I pulled the plugs and found NO brake fluid!

I was quite surprised, as I hadn't noticed any brake fluid puddles on the hangar floor, none in the cockpit and no leaks when I did condition inspections the last two years. I just assumed that, being in a "closed system" like that, there's no place for the fluid to go and that the level really didn't need to be checked. Wrong.

I still can't explain where three years' worth of brake fluid went, but I topped off the right one in the reservoir because I still had firm pressure, and drained the left system and refilled it from the bottom. I now have solid brakes again.

So, if you're assuming that your brake fluid reservoir is full because it was when you filled it and you haven't seen any leaks anywhere, you might want to check the fluid level to be sure. It's a good item to have on your annual condition inspection list.

Don,

Part of my pre-landing check is to apply the brakes checking for firmness of the pedals. If not firm, at least you are prepared to make a landing with one or both brakes inop.

Regards,

Brake fluid goes down with use...

Don,

Glad no one was hurt and no damage done.

Over time as you use the brakes the pads wear (duh, obvious I know) and the calipers pucks have to extend out further to engage the brakes. This requires more brake fluid for the pucks to reach out there. We have really small brake fluid reservoirs and this can consume most of your available reserve fluid.

You don't have to have a leak to need to add fluid. I always check my brake fluid every oil change. And I often have to add a small amount.

Good reminder of why.

N8RV said:

I pulled the plugs and found NO brake fluid!

I was quite surprised, as I hadn't noticed any brake fluid puddles on the hangar floor, none in the cockpit and no leaks when I did condition inspections the last two years. I just assumed that, being in a "closed system" like that, there's no place for the fluid to go and that the level really didn't need to be checked. Wrong.

I still can't explain where three years' worth of brake fluid went, but I topped off the right one in the reservoir because I still had firm pressure, and drained the left system and refilled it from the bottom. I now have solid brakes again.

So, if you're assuming that your brake fluid reservoir is full because it was when you filled it and you haven't seen any leaks anywhere, you might want to check the fluid level to be sure. It's a good item to have on your annual condition inspection list.

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Yikes!

Glad to hear you didn't bend any sheetmetal on your off-road excursion.

Back when I was having issues with the tailwheel not locking on the RV-8, I ordered a new rocket link arm and a new pin from Flyboy Accessories, and Vince emailed me a PDF that showed how to cut the notch into the arm a little deeper, and to put more of a blunt, almost squared-off nose on the pin with the edges radiused just enough to round them a wee bit, rather than the almost half-round semicircle shape of the stock pin. I carved the original arm's slot a little deeper with a rat-tail file and re-shaped the nose of the pin on the scotchbrite wheel and put the reworked old parts back on, and they've been locking perfectly since then. The new parts are still in the envelope, unused.

My RV-6 has a firewall-mounted brake reservoir with translucent plastic tubing running to all the master cylinders on both sets of pedals. One good feature of that is, it makes it easy to visually check the level just by looking down and seeing the red fluid in the lines. A bad feature is that every one of those nylon hose fittings everywhere in the system very slowly oozes hydraulic fluid a teeny-tiny amount, needing to be wiped off about once every few weeks before it seeps enough to drip onto the carpet, and of course, there's a need to add fluid to the reservoir which means pulling the top cowl off

Great post ...

...thanks much. Until now, I was thinking like you ... if there's no fluid on the hangar floor or on the A/C floor, there can't be any leaks. This is a great item to add to weekly/monthly maintenance checks.

Rupester said:

...thanks much. Until now, I was thinking like you ... if there's no fluid on the hangar floor or on the A/C floor, there can't be any leaks. This is a great item to add to weekly/monthly maintenance checks.

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That's exactly why I posted it.

I was supposed to go to a picnic at a friend's private strip that weekend. Had I not gone flying and had my little excursion into the weeds at our home field, I might have experienced that little off-runway adventure right into a line of parked planes!

Sometimes we discover things that need to be passed on so that embarassing (and dangerous!) moments like that can be avoided by others.

Glad you found it helpful.

I check at every oil change

I check mine brake fluid at every oil change. There was a period when I had to keeping adding fluid, but I never saw evidence of a leak.

Eventually, I found the leak around the threads of the fitting that screws into the brake master cylinder on 1 pedal. The fluid had absorbed in the the carpet - which is why I never saw where the fluid was going. (Yes, I did have to replace the carpet)

Thanks for posting. I bet things like this happen all the time (some with worse results) but for whatever reason, people don't post it. The "Air Force" cannot learn from mistakes if people don't post them.

Swallow your pride and help your community!

Good post Don! You probably saved a few folks, myself included, from some dings.

Watch it when you replace your pads

Don,

When you replace your pads you will have to push the brake caliper piston in which will push fluid back into the reservoir. If they are full when you do this it will overflow.

Good point, Frank. I had planned to stuff a bunch of towels in there first anyway, just in case.

It's such a pain to take out the front baggage compartment floor that I gave serious consideration to cutting an access door into the floor. It would be MUCH easier to take out a dozen screws near the middle of the floor than to remove them from the edges where access is a pain. Something for new builders to consider as they make the baggage compartment floors for the RV-8.

N8RV said:

Good point, Frank. I had planned to stuff a bunch of towels in there first anyway, just in case.

It's such a pain to take out the front baggage compartment floor that I gave serious consideration to cutting an access door into the floor. It would be MUCH easier to take out a dozen screws near the middle of the floor than to remove them from the edges where access is a pain. Something for new builders to consider as they make the baggage compartment floors for the RV-8.

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First of all, my forward baggage compartment floor is different from stock. My floor spans the complete width of the compartment. I divided the floor into 3 removable sections to facilitate accessing various components (battery, brake reservoirs, boost pump & filter) located below the baggage compartment floor.

To service the battery or brakes, I just have to remove one panel. To service the fuel boost pump filter, I have to remove two panels. As you recommended to new builders, give this area some design thought to make this area more accessible.

Brakes

I check the reservoir every time I pull the top cowl. It gives me peace of mind, and it only takes a minute.
I also check the clear tubing as pre-flight.

As for the overflow, I have rigged up a 1/8" brass 90 NPT fitting that screws into the reservoir and fits the clear vinyl tubing. I use it to recapture fluid while bleeding the brakes, and any time I am servicing them. It prevents
fluid making a mess by being pushed back through the reservoir.
I can also watch the tubing from under the plane while pumping fluid in from the bottom to see the bubbles flow down into the recapture can.

it works slick. (no pun intended...)
Jim F
RV-9A N571DF
250 hrs.

Jim F said:

... As for the overflow, I have rigged up a 1/8" brass 90 NPT fitting that screws into the reservoir and fits the clear vinyl tubing. I use it to recapture fluid while bleeding the brakes, and any time I am servicing them. It prevents fluid making a mess by being pushed back through the reservoir ...

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Stellar idea. Unfortunately, with the reservoirs mounted on the brake pedals, monitoring the fluid flow isn't possible from under the fuselage. However, it would make the job a bit less messy by putting a collection cup under the fitting/hose and catching the overflow rather than sopping it up with a towel.

Note to self: get a couple of 90* fittings

I don't remove any panels (or the cowl) to service the reservoir. No plastic lines. No plastic fittings through the firewall to melt in a fire. Fire resistant fluid too.