Brakes Can be a Real Drag
12/19/20 - After my last flight on 12/12/20, as I was pulling the airplane back into the hangar the right brake seemed to be dragging just a bit. I figured it was just some dirt and junk on the caliper pins so I planned to pull the wheel pant and clean and re-lubricate the pins.
As I was taking the wheel pant off I got some black sticky goo on my fingers. At first I hoped it was just left over mud, but everything else was dry and mud isn't sticky. Unfortunately it turned out that it is was brake fluid mixed with dirt.
I pulled the cylinder out of the torque plate to get a better look at it and, sure enough, it was leaking a little. Not enough to leave a drop of fluid on the ground, but enough to need to be addressed and also, possibly, enough to keep the piston from fully backing off when brake pressure was released.
Replacing the actual O-Ring is easy enough, but that means draining the fluid from the system and then having to re-service and bleed the whole system.
In the past I had lubricated the pins with some CRC Dry Graphite Lube spray lubricant I got from Aircraft Spruce. It works well and doesn't attract dirt and junk, but it is a bit of a pain to apply since it has to be sprayed on and it is important not to get any on the brake pads or disc.
At the recommendation of a friend, this time I used some CRC 05361 Silaramic Brake System Grease. Apparently it is what his mechanic uses. It is a grease specifically designed for brake system parts that doesn't attract dirt and grit and is good for high temperatures. It was easy to apply and a tube will probably last the rest of my life.
The best way to service and bleed the system is to pump fluid in through the bleed fitting at the bottom and out through the reservoir at the top. While there are fancy contraptions available to do this, they are rather pricey for those of us who only do this once every few years. Most people use a standard pump oil can to pump fluid into the system. The set up that I have been using pumps almost as much fluid onto the floor as it does into the system because the hose I was was the wrong size.
The issue is that if you use a hose sized for the bleed fitting on the brake it is too small for the oil can, but if you use a size appropriate for the oil can it is too big for the bleed fitting. A truly smart and well equipped person would make a hose with proper fittings and reducers to get the job done. In my case, I just used two lengths of different sized plastic hose. Of course, I only had two sizes on hand, too small and too big, so I had to make a trip to the aviation department at Lowe's.
Once I got the right size hose it was easy to make up what I needed. I put the smaller diameter hose inside the larger and sealed the joint with some Rescue Tape.
Once that was done a hose clamp at the oil can and I was ready to go.
In retrospect, I should have wrapped some Rescue Tape around the oil can nipple, which would have made a better seal with the hose. As it is, this went from dumping half the fluid into the drip pan to just leaking a few drops.
I had a friend around to help with things like watching the fluid coming out of the reservoir to tell me when it stopped having air in it so I could stop pumping and close the bleed valve, but I thought he might be getting bored so I told him I could handle it by myself and that he could go home if he chose.
OK, so how do I do it myself. I am pumping down at the brake and need to see what comes out of the reservoir at the top of the fire wall. Hmmm. Hey, I have a ton of video cameras around and at least some of them will interface with my phone. All I have to do is put a camera on the jar and look at my phone as I pump.
I clamped a stick to a tripod to to clamp the camera to.
This is what I saw on my phone.
That made it very easy to get the system properly serviced and all the air out. I pumped the brakes and they felt good, a quick leak check with no leaks detected and it was time to put it all back together.
Now I can't wait to go try it out.