How do I bleed the brakes

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Leesommer
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How do I bleed the brakes

Post by Leesommer »

Does anyone have a detailed step-by-step on how to bleed the brakes they seem to be a bit soft and when I put the parking brake on and advance to throttle around 1500 RPM the brakes start to release and and will not hold. Therefore I’m thinking I need to bleed them. It just feels soft. So if anybody’s got a detail procedure on how to do this please let me know
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Rick
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Re: How do I bleed the brakes

Post by Rick »

Here is the "official" procedure from the DA40 AMM:
Bleed Brakes.pdf
(78.67 KiB) Downloaded 252 times
although it seems like we did this a while back and there was no "equipment" involved, so hopefully someone will chime in with more infomration.
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Leesommer
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Re: How do I bleed the brakes

Post by Leesommer »

Thanks Rick
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RMarkSampson
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Re: How do I bleed the brakes

Post by RMarkSampson »

PDF is spot on - but overstates the process. It is really easy to push fluid from the brake caliper "up" to the reservoir. It removes any air in the process. I use a small oil can pump - think I got it off Amazon.com and a small piece of hose hat fits over the nipple on the brake caliper. I also don't have the overflow equipment quoted in the PDF. I simply remove the reservoir cap and stuff a sacrificial rag to catch the overflow.

It is best as a two-person job. One to watch the top of the reservoir and say "stop" when it if full (a light and an inspection mirror is handy). The other person just opens the nipple at the bottom - hooks up the oil can filled with brake fluid and starts pumping. When you hear the "stop" you stop pumping and close the nipple. Note that you only loosen the nipple - not the entire fitting sticking out of the caliper. Once done, replace the reservoir cap, clean up any overflow, and you are complete. Be sure you pump the brakes before starting up the engine - or you might be doing it very quickly (frantically?) once the prop is spinning. Using chocks post-maintenance is not a bad idea.

I believe the AMM for the DA-20 has a "three year" replace all brake fluid recommendation - likely for all Diamonds. In that case, simply open the nipple and remove the reservoir cap to allow all the old brake fluid to first drip out - then you will obviously do a lot more pumping to fill the brake system back up. Because my oil can is fairly small I needed to refill the oil can once to get the brake fluid to the top.
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Re: How do I bleed the brakes

Post by Rich »

You don't want to fill the reservoirs too full or they can ooze upon the fluid getting heated. I made a dipstick out of a zip tie to conform to the levels specified in 32-40-00 of the maintenance manual. Also I discovered that one of the vented plugs on the reservoirs was not vented, so I corrected that with a small drill bit.
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Re: How do I bleed the brakes

Post by smoss »

anyone else tackle this job themselves yet? Specifically, what was used as an overflow tube? Any common fitting that matches the reservoir filler hole treads and can be attached to a tube?
Steve
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Tim H
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Re: How do I bleed the brakes

Post by Tim H »

I've never done it myself but I can echo the comments about the overflow. I walked into the shop when the A&P was bleeding my brakes (actually he was finished bleeding the brakes and he and his assistant were cleaning brake fluid out of the rudder pedal area of my DA40). What a mess.
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Rich
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Re: How do I bleed the brakes

Post by Rich »

smoss wrote: Wed Nov 20, 2019 4:23 pm anyone else tackle this job themselves yet? Specifically, what was used as an overflow tube? Any common fitting that matches the reservoir filler hole treads and can be attached to a tube?
The filler cap is 1/8-27 NPT fitting. Should be able to figure out something from that. Try this:
https://www.amazon.com/NIGO-Brass-Hose- ... 7&sr=8-112
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Re: How do I bleed the brakes

Post by Sandy »

I was going to fly Young Eagles this past Saturday, but when I got to my hangar I noted brake fluid dripping from the right brake. As set forth in one of my prior posts ("Two wrongs don't make a right... but three lefts do") viewtopic.php?f=8&t=5837&p=63288&hilit= ... ngs#p63288 I have learned that that means the brake pads have worn down so far that the piston pushes out to the point that brake fluid can escape past the O-ring. It's a simple matter to replace the brake pads, so I now keep spare brake pads, brake pad rivets, a rivet removal/installer tool, brake fluid, a filler bottle, and spare O-rings in my hangar. While I was able to replace the worn brake pads, when I tried to "condition" the new right pads I found that I needed to bleed the right side. I could not do that alone, as someone needs to be "pumping" brake fluid into the system from the brake end while someone else monitors the overflow at the reservoir end. In order to avoid messy overflow, I made up a "drain" tube from 3/8" ID tubing that I attached to a spare reservoir cap (with a hole in it) using a small hose clamp. I screwed that into the reservoir, while my mechanic pressure fed fluid into the system. While I held the end of the overflow tube in a small container, my mechanic pumped additional fluid into the system, and then all was well again.

Let me know if you would like me to post pictures of the drain tube.

Sandy
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Re: How do I bleed the brakes

Post by Rich »

Sandy wrote: Wed Nov 20, 2019 7:29 pm I was going to fly Young Eagles this past Saturday, but when I got to my hangar I noted brake fluid dripping from the right brake. As set forth in one of my prior posts ("Two wrongs don't make a right... but three lefts do") viewtopic.php?f=8&t=5837&p=63288&hilit= ... ngs#p63288 I have learned that that means the brake pads have worn down so far that the piston pushes out to the point that brake fluid can escape past the O-ring. It's a simple matter to replace the brake pads, so I now keep spare brake pads, brake pad rivets, a rivet removal/installer tool, brake fluid, a filler bottle, and spare O-rings in my hangar. While I was able to replace the worn brake pads, when I tried to "condition" the new right pads I found that I needed to bleed the right side. I could not do that alone, as someone needs to be "pumping" brake fluid into the system from the brake end while someone else monitors the overflow at the reservoir end. In order to avoid messy overflow, I made up a "drain" tube from 3/8" ID tubing that I attached to a spare reservoir cap (with a hole in it) using a small hose clamp. I screwed that into the reservoir, while my mechanic pressure fed fluid into the system. While I held the end of the overflow tube in a small container, my mechanic pumped additional fluid into the system, and then all was well again.

Let me know if you would like me to post pictures of the drain tube.

Sandy
You can use the piece I posted with 1/8 in. hose to replace the vent cap and push fluid one way or the other. I have a vacuum pump-based gizmo to use for this function. Can be done with one person.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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