Adam,

 

TOO LONG NO TALK TO YOU!

 

I replaced may Poly-flo lines with SS/Teflon hoses during construction…except for the section from the co-pilot pedals back to the reservoir. (My brake lines run from the reservoir to the CP to the Pilot pedals, then through a parking brake valve to the brakes. Not as recommended by Lancair for the IV-P, but fewer connections, etc in the critical path from pilot pedals to brakes.) All lines from the co-pilot pedals to the brakes are SS/Teflon or hard aluminum.

 

The Poly-flow section allows me to see the bubbles in the last part of the circuit at least… I also take the cap off the reservoir and replace it with a 1/8” pipe thread fitted with a tube end for bleeding. Put a clear tube on this fitting and run it into an overflow bottle. Then push fluid up from each brake caliper in turn until it comes out the reservoir without bubbles. You’ll have to do this a couple of times when you’re first getting going, for a couple of reasons, but once you get the air out, the brakes will not need servicing for a very long time unless you spring a leak.

 

As to the reasons for re-servicing initially: The first is air dissolved in the brake fluid. This is caused by leaving the servicing pot pressurized when not in use. Minimize/eliminate this problem by dumping all the pressure after each use. If you find the pot pressurized, dump the pressure, sit it outside in the sun to heat up and give it a couple of days to “de-gas” before servicing your brakes. The other cause is air that’s trapped as small bubbles inside the lines…especially any solid aluminum ones. These will slowly consolidate into bubbles/air sections over time from normal braking action/agitation of the fluid. A re-bleed just prior to your high speed taxi testing, with verification that you have good/firm brakes is needed in any case; then another at the end of your flight testing and you should have very solid/good brakes from that time forward. …at least it worked that way for me… J

Bob

 

 

It has been strongly suggested that I replace my Poly-flo/Tygon brake lines with braided stainless steel Teflon hoses. How do you bleed such a system? It seems that it would be extremely difficult to get the bubbles out if you can’t see them! I a brake bleeder so I can push the fluid in from the caliper end, but since the Lancair reservoir is metal my first indication of progress will be dripping from the overflow line!

 

How to those of you with non-transparent lines bleed your brakes?

 

Thanks,

Adam Molny

Legacy #151

Interior painted, instrument panel out for silk screening