Puzzling brake issue

[gerrychuck]

Last fall I ran into a problem with the passenger side brakes in my RV6A; on rollout with my pilot son flying from the right side, he calmly informed me that I should take the airplane as he had no brakes on his side. In checking things out after, they would not firm up with pumping, were both affected, but the pilot side pedals were perfect. At annual in September I got the boys from the FBO over with their pressure pump and we bled the system from the bottom up repeatedly. Could never get rid of a little air in the supply lines from the reservoir, but research here tells me that is fairly normal. All pedals nice and firm when finished. No one has flown from the right seat since, so I thought I should check the pedals yesterday; both very soft again, although the left firmed up with a few pushes. Right stayed completely soft. Pilot side pedals fine. I am not sure whether my cylinders are Matco or Cleveland (kit first flew in 2003; not sure when the kit was sold) but I suspect Matco. I will get pics today. At this point I am wondering whether my best option is to just go ahead and rebuild the cylinders on the passenger side and be done with it. My suspicion is that those seals have broken down earlier than the pilot side because they are so rarely exercised.

Any thoughts? Also, if they are indeed the Matco's, does anyone have a quick reference on the part number of the rebuild kit? Thanks in advance.

[flightlogic]

I would check the forums here for kits you can build up from Harbor Freight stuff to make your own bleed system. You probably have a bit of air still hiding somewhere. Doing it yourself... from the bottom up is best. Make a container to catch the overflow.... and let it rip. Takes a bit of effort and is messy no matter how careful you are. You will know your brake system that much better IMHO.

[Larco]

Have you checked the fluid level? If you have a leak and the reservoir becomes empty the right side will be the first to go.
I have actually seen this happen! Someone didn't know to check the fluid and it was empty and the right brakes were inop. :-)

If this is the case a bleed might be necessary after the fill up to get rid of air in the cross over lines.

Larry

[gerrychuck]

Originally Posted by LARCO

Have you checked the fluid level? If you have a leak and the reservoir becomes empty the right side will be the first to go.
I have actually seen this happen! Someone didn't know to check the fluid and it was empty and the right brakes were inop. :-)

If this is the case a bleed might be necessary after the fill up to get rid of air in the cross over lines.

Larry

I haven't checked it yet this time around. When I had the same problem back in September the level was fine. Looking at the cylinders and lines today, there is a lot of air in the supply lines, almost right down to the cylinders. I'll pull the upper cowling and check next weekend.

Cylinders are Matco, by the way. Corkscrewed my 6'3" frame down there to read the label on the outside of the right cylinder; not an easy read at age 56 from 3" away! Thank god for cell phone pics....that worked better.

Flightlogic: those brakes were very thoroughly bled, from the bottom up, with a pressure pump, and we did it several times just to make sure. And yet...no matter how many times we did it, there always seemed to be a bit of air in the supply lines. Very odd.

[Ron B.]

Matco brakes in my SuperCub. Had an issue bleeding a while back. I was informed the position of the master brakes to the horizon makes a difference. The poster on Supercub.org suggested I dis-mount the master cylinders and rotate them before bleeding. It was much easier for me to just lift the tail of (tail wheel AC) the aircraft up higher than the nose. Bleed fine the first try this way and I have been doing this every conversion (back from floats) with the same results.

[9GT]

Whenever I help my building buddy bleed the brake system on his Cozy MKIV, we have to un-mount the parking brake valve and manipulate it a bit while pressure pot bleeding from the brake caliper to get all the trapped air out. If we don't do that, the brakes remain spongy no matter how much fluid gets pushed through. We spent a lot of time on those brakes before we figured out where air was getting trapped.

[Raymo]

All good suggestions above but I agree with your assessment above that if bleeding does not fix the right side, rebuilding the cylinders will be needed. Very easy compared to the bleeding that will be required afterward

[guccidude1]

Check out my post 6 Jan 16 on soft left brake on CP side only.

http://www.vansairforce.com/communit...ghlight=brakes.

Check your reservoir level or check for stains running down the firewall. Dan from Reno

[Mike S]

Dan, did you ever figure out what was the cause of the problem with your brakes?

[gerrychuck]

Thanks to all for the input. I will investigate further this weekend.