Bob and Ryszard:
I have always used DOT5 because a friend
nearly lost his Longeze after a landing and
too much braking. He had some brake fluid
FLOWING out and a fire. Got a heavy
coat around it.
I have Grove brakes. Checked with them.
The seals are Viton so I guess it is safe.
Grove will not recommend DOT 5 because
they could get approval (from the FAA ?)
for anything but the dangerous red crap.
There is another FAA mistake/failure.
I wonder how many other buers use DOT 5
I've never put that flammable red crap in any of my planes and never will. Dot 5 is the only way to go. I have Cleveland's and use 50 cent NAPA O-rings so change them out every 500 hours or so (takes about 15 minutes when changing pads). After that I put a couple of reversible bar clamps between the thigh rest and brake pedal and pump them up to 100 pounds or so. Let sit overnight, next day check for leaks. no leaks ever. So far..... so good.
My experience is with single puck Clevelands on my LongEz. My brakes use the MS28775 O-rings in a slightly smaller size.. However, I replaced the originally spec'd Buna-N O-rings for Viton O-rings. Viton has superior high heat tolerance. When I did my research, others had reported contacting Parker-Hannifin and the tech there had no issues against using Viton.
Did you verify if the leak is from the O-ring, the bleeder, or the fittings? I suppose you use silicone based brake fluid because it is not hygroscopic and less flammable than the standard aviation 5606 fluid. Maybe that is why you have leaks since the system is designed for the standard fluid, not the DOT5.. In my opinion, aircraft should not use DOT5 because it is not compatible (miscible) with the standard red fluid and, if getting help from an A&P away from home base, he may add standard fluid and cause a bad situation for you. I use a less common, but compatible aviation fluid, spec'd as #83282. Its also known as Aeroshell #31 or Rayco #782. It is red, 100% compatible with the standard 5606 aviation brake fluid, but has a much higher flash point.
On Sun, Jul 7, 2019, at 2:39 PM, john toelaer johntoelaer@...
.... but I made a logbook entry that the o-ring is MS28775-222
Now I am ready to fly but one piston is leaking. I replaced the Ms28775-222 with a new one from aircraft spruce but no joy. ...when I get back to the hangar I had overheated the good brake and it was leaking also.
I use dot 5 silicone brake fluid. Aircraft Spruce sells a Ms28775=222 for 65 cents and also a Parker -Hannefin equivalet for about 20 bucks. I ordered
both because the cheap one has a speck thickness of 0.125 but the expensive one is 0.139 thick (may be within the + or minus tolerance, don't know)
Any help would be appreciated.