Bleeding brakes from bottom up

[Blueadventures]

25 minutes ago, danny_galaga said:

I realised after I ordered it that this device probably entails adding oil into the reservoir 😄. But it's only 23 bucks. Considering how much I've blown on a project I'm not even interested in anymore, it's chump change!

So in the end maybe the syringe and hose will do what I want. I'm in Noumea right now. Maybe next week. If I fix the brakes I can taxi it. Might help make me excited about it 

Sounds a good plan; enjoy.  (Tip; have available the small bottle and hose like I described in case you need such.)

Edited November 10, 2023 by Blueadventures

[RFguy]

I only open the nipple a crack and consider the liquid a reasonble seal in the thread.... 

[skippydiesel]

1 hour ago, RFguy said:

I only open the nipple a crack and consider the liquid a reasonble seal in the thread.... 

The downside of a slow flow (nipple a crack) is that you don't get the potential benefit of scouring and the job will take a lot longer.

Edited November 10, 2023 by skippydiesel

[facthunter]

The only way to ensure the bubbles move and are  expelled is to have the fluid flow faster and prolonged. The bleed nipple is always mud/rust blocked if the little rubber cover is gone. You often have to use a small drill to clean it out. If the Master cylinder is old it may allow air in when the pedal is raised and you'll never get it right. (Hard pedal).   Old master cyls will often fail by slowly sinking to the floor. Not so good if you're holding to allow an RPT to take off before you cross the runway.  Nev

[danny_galaga]

All new on my plane. By the time it's not, I'll probably have sold it.

 

That was a concern about bottom up- you might be pushing crap into the system. But like I say, all new for me.

[facthunter]

That's a reasonable concern. The bleed is  on the TOP of the cylinder, primarily to remove AIR.. IF the system is really contaminated, flush and overhaul the LOT. I empty the Master reservoir first and top up with clean oil immediately. if it's just a bleed required.  That means you KNOW the master cyl is OK. Nev

[skippydiesel]

Master reservoir??

I guess there may be more than one (I have only only ever seen, where the hydraulic clutch has a separate reservoir to the brake system) but they are likely to be equal. Perhaps some aircraft have two - still would not be a master.

I know I am being picky (apologies) but it's a brake fluid reservoir. The master is usually the cylinder (further downstream to the reservoir) which compresses the fluid on applying pressure to the foot brake or toe. - the compressed fluid then activates the slave cylinder(s) which in turn applies the brake pad/shoe to drum/disk.

 

True some motorcycles and light aircraft, have an integrated reservoir/master in the one casting and for the uninitiated the reservoir on may vehicles is piggy backed on to the master cylinder.

 

In general master cylinders are not bled but with aircraft who knows!

 

In my experience the slave cylinder bleed nipple is always at the highest point of the installed slave cylinder  - assuming correct installation.

[facthunter]

Master cylinder is inferred. I even said so later in the same post. I've replaced a master cylinder  that didn't survive pushing to the floor a lot of times and only bled there with the new one as that's all that was needed.. You are ridiculously PICKY. You have absolutely NO idea how much brake and clutch work I've done in a lifetime..  Nev

[Blueadventures]

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Edited November 12, 2023 by Blueadventures

[Blueadventures]

All replies are general in nature; if the specifics of the type and brand / model of brakes Danny has then can be more specific with replies.  (For example the the skyranger brake I have is a single lever / master cylinder combinatioin and when it did not work first up out of box it required a quick home with some fine wet and dry in kero then has been perfect ever since 6 years and 360 hours.

[facthunter]

That would be one that uses mineral based oil OR use a jet of water and a bottle brush to remove the kero and hone grit and the dry off all water.  You CAN buy rubber grease for some assembling. NOT mineral based oils. Nev

[danny_galaga]

Sigh. Ok, I don't have the manual handy but these look much like the parts. Same brand. Boy they make a lot of variations! System has four master cylinders (toe brakes) , a hydraulic park brake (illustrated is definitely the exact model) an external caliper on each main wheel for a total of two external calipers, and a reservoir some height above the toe brakes. Tubing is plastic. It's all so complicated I seriously wish I'd bought the tricycle model- I'd just install a handbrake like on the nynja.

 

https://matcoals.com/product/master-cylinder-short-mc-4gh/

 

https://matcoals.com/product/be5-brk-assy-no-plt/

 

https://matcoals.com/product/parking-brake-valve-dual/

 

 

 

 

[Blueadventures]

1 hour ago, danny_galaga said:

Sigh. Ok, I don't have the manual handy but these look much like the parts. Same brand. Boy they make a lot of variations! System has four master cylinders (toe brakes) , a hydraulic park brake (illustrated is definitely the exact model) an external caliper on each main wheel for a total of two external calipers, and a reservoir some height above the toe brakes. Tubing is plastic. It's all so complicated I seriously wish I'd bought the tricycle model- I'd just install a handbrake like on the nynja.

 

https://matcoals.com/product/master-cylinder-short-mc-4gh/

 

https://matcoals.com/product/be5-brk-assy-no-plt/

 

https://matcoals.com/product/parking-brake-valve-dual/

 

 

 

 

Have you watched this video? 

 

[skippydiesel]

Hi Blue,

 

I haven't taken the time to view the whole of the video - if the presenter just had a normal verbal delivery rate it would be 1/4 the length.

 

I have a similar system to the Matco - as I said previously don't get too hung up on using just one system to bleed the brakes. If one does the job, great! but if not be prepared/flexible.

 

My brake line have a very small bore, guessing about 2 mmm. I had a lot of problems with air staying in the system. Pressure filled up, toe brake pumped down, vacuum bleeding, tapped and tapped the lines slowly moving bubbles and even tried (with extreme care) air pressure into the reservoir  - it all helped.  Took a while but eventually got all the bubbles out - persistence paid. 

 

FYI the park brake is just a valve - not hydraulic (or at least mine isn't). In my system, I can pull the park brake on  either after pressurising toe brakes or befor ie it acts as a one way valve to retain pressure. Pushing the park brake in just releases the pressure in the slave cylinders thus releasing the brakes.

Edited November 13, 2023 by skippydiesel

[facthunter]

To get air out of a calliper or wheel cylinder it has to exit at the top. A small bore pipe will make the bubbles move faster and further  for a given volume of oil..  Nev

[danny_galaga]

For all their inadequacies, I wish it was all cable operated!

 

Although, having said that, cables on toe brakes would be quite a nightmare. What I have now is merely a bad dream in comparison 😄

Edited November 13, 2023 by danny_galaga

[Blueadventures]

6 minutes ago, danny_galaga said:

For all their inadequacies, I wish it was all cable operated!

 

Although, having said that, cables on toe brakes would be quite a nightmare. What I have now is merely a bad dream in comparison 😄

I'll come together for you.  Follow the video should be a good start.  Brakes can test your patience at times, know this from experiences; many over the years.

[facthunter]

Yeah the Auster's heel brakes are a bit ordinary. Toe is  far  more conventional.  Modern Cables might be a lot better especially if you can grease them.  Nev

[danny_galaga]

2 hours ago, facthunter said:

Yeah the Auster's heel brakes are a bit ordinary. Toe is  far  more conventional.  Modern Cables might be a lot better especially if you can grease them.  Nev

 

Yep, I actually think if I had a tricycle, I'd set up cables on a hand brake. Who cares you have to adjust it every now and then? At least it will be easier than adjusting drum brakes on a car, and they were hydraulic to boot- worst of BOTH worlds 😄

 

 

[facthunter]

I think they must be differential for sharp turns if nothing else. Tricycle undercarriage is here to stay unless you go on really rough & rotten strips often.  For the lighter planes I think Cables could be worth a shot. Nev

[sfGnome]

8 hours ago, skippydiesel said:

 

I haven't taken the time to view the whole of the video - if the presenter just had a normal verbal delivery rate it would be 1/4 the length

Many (all?) YouTube displays have a replay speed setting - very handy for the slow speakers. I just set that video to 1.75 times and got through it in no time. You could probably set it even faster and still have it entirely understandable. 

[danny_galaga]

2 hours ago, facthunter said:

I think they must be differential for sharp turns if nothing else. Tricycle undercarriage is here to stay unless you go on really rough & rotten strips often.  For the lighter planes I think Cables could be worth a shot. Nev

I have what I have. Which is a tail dragger ultralight. I find on the tricycle undercarriage Tecnam I hire, if I want to do a sharp turn, I press down down hard on the pedals and wrench the hand brake at the same time. Feels much the same turn as a Warrior with toe brakes.

 

In the hangar is a, I want to say Australian Lightwing. So I will 😄 which is tricycle and cables and drums. I doubt it could stop as quickly as my setup, but I wouldn't care either. Just operate it within its capabilities.

 

[danny_galaga]

On 08/11/2023 at 8:01 AM, skippydiesel said:

I use disposable syringes (purchase from chemist or animal feed merchants) & clear hose to suit (Bunnings) - low cost & can, with care (flush with metho or Iso, lube plunger with silicon)  be reused several times. The amount of brake fluid is very small, so a 100 mm (or smaller) syringe will usually do the job.

 

Don't get hung up on bleeding from the bottom - you may find that you bleed from wherever, to get that last bit of air out of the system.

 

If possible never drain your brake system ie when replacing fluid, use fresh unused fluid to flush the system, avoiding air entry.

Hey I bought a syringe 💉. Did the left brake first. When I did the right brake, damned if I didn't see quite a few bubbles coming up into the reservoir! Reservoir is on the right, so I couldn't see what was happening on the left. 

 

Note that I first set up the brakes several years ago, doing the traditional pumping method. So in a sense I've done several techniques as you recommended 🙂

 

[skippydiesel]

Hi Danny - how well you have managed to remove the air may not be apparent at the time .

 

Unfortunatly, it is not unusual to think you have done a sterling job (100% free of air) only to find a few hours later that one or both brakes are "soft" - take a deep breath and go again.

 

I hope it doesn't happen but if it does carefully examine each brake line (assuming yours are transparent) for air bubbles, especially where you may have  a high curve. It may be possible, while flexing the tube to have an up slope,  to rapidly tap the line, encouraging the bubbled to migrate towards the reservoir. Otherwise its back to pressure fill from bottom and or pressure empty down, by pumping the brakes.

[danny_galaga]

I suspect that air was trapped in the park brake. 

Since I had to buy a quart of oil 🛢️ I may as well waste some. I will probably do a 'car' brake pump again soon. Lines are black unfortunately..if I ever replace them, I'll get clear for sure. Makes sense 😎