How do I bleed the brakes

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Sandy
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Re: How do I bleed the brakes

Post by Sandy »

@Rich

I'm with you on using a vent cap with a hose attached, but you lost me after that regarding the way you do a one-man bleed, as I was dead in the water when I realized that I was alone and had to bleed mine. If I had realized how worn the pads were before they got to the point that they allowed leakage I could have replaced them without need to bleed the brakes, so I will be more careful about brake wear in the future.

Could you post a picture or provide details of the "vacuum pump-based gizmo" and how you use it?

If only one person is doing the brake bleed, and the gizmo thing is vacuum based, does that mean that you use a long hose from the reservoir that goes down to the gear while you somehow open the bleeder valve at the brake to add brake fluid? Or do you fill the reservoir and use the vacuum gizmo to suck brake fluid at the brake bleeder?

Sandy
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Rich
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Re: How do I bleed the brakes

Post by Rich »

Sandy wrote: Wed Nov 20, 2019 9:21 pm @Rich

I'm with you on using a vent cap with a hose attached, but you lost me after that regarding the way you do a one-man bleed, as I was dead in the water when I realized that I was alone and had to bleed mine. If I had realized how worn the pads were before they got to the point that they allowed leakage I could have replaced them without need to bleed the brakes, so I will be more careful about brake wear in the future.

Could you post a picture or provide details of the "vacuum pump-based gizmo" and how you use it?

If only one person is doing the brake bleed, and the gizmo thing is vacuum based, does that mean that you use a long hose from the reservoir that goes down to the gear while you somehow open the bleeder valve at the brake to add brake fluid? Or do you fill the reservoir and use the vacuum gizmo to suck brake fluid at the brake bleeder?

Sandy
I don't have a picture of it in use, but this is the vacuum bleeder I use. It does require an air compressor to generate the vacuum (it works, trust me):

https://www.amazon.com/dp/B00OM751EC/re ... NrPXRydWU=

1. Put adapter in vent opening.
2. Put this bleeder on the floor in the plane, with vacuum line attached.
3. push the bleeder adapter on to the vent adapter.
4. Place container on hangar floor with hydraulic fluid in it.
5. Attach an appropriate hose to the bleeder valve on the brake caliper.
6. Place other end of hose down into the fluid container.
7. Loosen bleeder valve on the brake caliper.
8. Press operating handle on the vacuum bleeder. Hold until all the bubbles stop and/or brake fluid has been fully replaced.
9. Release vacuum bleeder handle.
10. Tighten the bleeder valve.

After removing the vent adapter, you should suck a bit of fluid out of the reservoir to leave an air space.
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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Re: How do I bleed the brakes

Post by Sandy »

@Rich

Thank you for the explanation and the item reference. I now understand that your approach involves connecting a brake fluid container located on the hangar floor adjacent the caliper to the bleeder valve so that you can suck fluid from it using the vacuum brake bleeder that is in the plane. I understand that you would then stop sucking brake fluid when there are no more air bubbles coming out of the reservoir vent plug line. At that point you would have to close the brake bleeder valve at the caliper, then disconnect the adapter at the reservoir vent opening.

The method we used involved forcing brake fluid into the bleeder valve using a hydraulic brake bleeder tank https://www.aircraftspruce.com/catalog/ ... ertank.php along with a tube connected to the vent plug in the plane. I’m now thinking that if I attached a longer tube to the vent plug, I could run it out of the cockpit to a container and use the pressure tank so that all fluid is outside the cockpit and the bleeder valve could be closed by the person operating the pressure pump. A valve could be added to the overflow tube adjacent to the vent plug so that any brake fluid in the overflow tube could be trapped when the overflow tube and vent plug are removed. This approach would eliminate the need to use a compressor to operate the Venturi on the vacuum system, and it would also allow a single operator to do everything outside the cockpit. I wonder whether a brake bleeder adapter could be fitted to the end of one of these pressurized sprayers https://www.homedepot.com/p/HDX-1-Gal-P ... /307766754 to make a very inexpensive brake bleeder system.

It looks like this Cleveland brake bleeder adapter could be used
https://www.aircraftspruce.com/catalog/ ... ts1246.php

Thoughts?
Sandy
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Rich
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Re: How do I bleed the brakes

Post by Rich »

I like the vacuum-based approach because I can use the same device for the plane and my bike, which use incompatible types of fluid. Plus with everything in suction, there is less likelihood of something popping loose. This device has a check valve so the air/fluid won't flow back into the system when the vacuum is relieved and the bleed valve has not yet been closed.

Incidentally, I do this in reverse on my bike, pulling the brake fluid, along with any bubbles, from the reservoirs (I have three) down to the brake calibers and clutch slave cylinder. It works just fine this way, also. But in the case of the plane, it would be sucking extra air into the system at the start.
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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Re: How do I bleed the brakes

Post by Sandy »

@Rich

Thank you for the explanations. I think that the next time I need to bleed my brakes I will attach my electric tug and pull it from Atlanta to Oregon so that you can show me how it’s done.

Sandy
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Re: How do I bleed the brakes

Post by Sandy »

@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?
Here is what I used. It's a short length of 3/8" tube that's attached to a vented reservoir cap using a small hose clamp. I had an extra reservoir cap, but since it's not damaged, you can use the one that's already on the reservoir as long as you don't cover, and seal off, the vent hole.
IMG_1804.jpg
IMG_1803.jpg
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Rich
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Re: How do I bleed the brakes

Post by Rich »

A couple of bucks from Ace:
Brake Vent Adapter.jpeg
Adapter on Reservoir.jpeg
Apparently the new design for this reservoir allows for unscrewing the top of the reservoir for filling. Mine is all welded and one must use the vent fitting for filling/bleeding.
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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