Found Water in Brake Wheel Cylinder

[MoonlightVFR]

Removed piston from right wheel cylinder - new Cleveland Brakes 700 hours ago.

Brakes were O K in function. Just decided I want new 0 ring in both wheel cylinders.

Became suspicious as wheel cylinder piston was being breached from Right cylinder.

A watery exude dripping w dark particles. I did not like that at all I wanted to see bright reddish aviation brake fluid immediately.

A little less than a third of a teaspoon of watery mixture came out first. Then the red.

Inside the cylinder was a little distressed, gooey on back of piston. Removed w mineral spirits and Goof OFF.
No corrosion but did remove black bits. Baked on rubber residue ?

Cleaned piston; placed in Freezer. Slight heat gun on new 0 ring, slight, bathed in brake fluid. moderate heat on
brake cylinder housing. Slip new 0 ring on cold piston, wipe brake fluid on piston. Easily press piston into cylinder.
No damage to new 0 ring in installation.
Add brake fluid purge air. Holds tight cannot rotate tire by hand while AP assistant pushes pedal.

Left wheel cylinder was like NIB no issues.

Good feeling looking down at brakes from above and seeing shiny bright clean brake pistons extended and clamping
brake rotor tightly.

I wanted to share the surprise. Slight water in right brake cylinder. What about yours?

New replacement wheel cylinders may possibly cost 650.00 each.

[DWood]

Cleaned piston; placed in Freezer.

Not being critical just courious. Why did you place the piston in a freezer?
Thx,
Dan

[c170b53]

I know what you're saying as I've seen the similar thing. There's no fluid flow in the system so the brake fluid in the caliper resides in the caliper and as such is subject to degradation from heat, moisture, and foreign particles aka dust. For those that don"t bleed the brakes, the fluid will degrade and the caliper will accumulate substances that will eventually cause the caliper to be rendered unairworthy. Big emphasis on eventually here but as the prices on parts seem to be heading like everything else in aviation, to Mars, possibly preventive maintenance has its advantages over fix it when its broke.

[c170b53]

Why did you place the piston in a freezer?

= To check on the ice cream ? (happens at work all the time ).

[canav8]

Coincidentally, replacing my 170 gear for 180 gear I found the same problem. I am a little confused since I have never found fluid exchange. The puck had a high amount of clear fluid in the caliper even after I have bleed the brakes from the bottom up and have never found the puck to leak. I just detached the caliper from the brake line since I am going through the whole thing. I dont have an answer and I have no idea how long it has been this way especially since I am notorious for changing fluids. Weird!

[c170b53]

I guess I've confused the issue, if you have air in the system then bleeding from the bottom to the top is the trick, but periodic bleeding to replace the fluid in the calliper should be from the top to the bottom.

[canav8]

I guess I've confused the issue, if you have air in the system then bleeding from the bottom to the top is the trick, but periodic bleeding to replace the fluid in the calliper should be from the top to the bottom.

+1
I have done that. That is why I was surprised to see that i had a clear liquid in my caliper. I have no idea how long it was in there. D

[GAHorn]

Water in the brake caliper/cylinder is common with airplanes that have been pressure-washed. It also occurs when airplanes are taxied thru deep snow/ice as particles become impacted and forced past the O-ring, but the most common reason is pressure-washing. (This may not have occurred in your presence if you've had a shop perform and annual and/or wash-job.

Rarely it can occur as the result of condensation by flying in humid climes regularly...then an occasional climb to freezing temps or into cold climes... and condensation accumulates in the master cylinders. Oil (hyd fluid such as 5606) is lighter than water and the condensation sinks to the lowest point in the system.

It's a good idea whenever replacing brake linings to pull the caliper piston and flush/inspect the system. (And avoid pressure-washing wheels and taxying thru deep puddles or parking in deep water.)

[ghostflyer]

When doing a 100hrly or every 12 months why not push on the bleed nipple a piece of clear plastic tubing about 2 ft long and bleed the brakes a half a dozen pumps and also fill the brake reservoir . This will hopefully flush any degraded brake fluid or water .

[GAHorn]

...

I do the same on all my cars and motorcycles too. The DOT 4 brake fluid is really hydroscopic and the ooey gooey stuff starts appearing in about 18 months.

JUST TO BE CLEAR ON THIS..... do NOT use automotive brake fluid in an airplane. (Aryana is doubtless referring to his cars and motorcycles when using DOT 4 fluid.)

[falco]

When doing a 100hrly or every 12 months why not push on the bleed nipple a piece of clear plastic tubing about 2 ft long and bleed the brakes a half a dozen pumps and also fill the brake reservoir . This will hopefully flush any degraded brake fluid or water .

I do this at annual --- if the first couple squirts come out clean, there's not much left to do. Just part of my annual brake inspection. If its contaminated, that's easy to see in the first couple squirts and then I'd feel compelled to do a more complete flush.

cheers,

Pete