bleeding brake help

[pintlar]

Marchetti Sportster...
.. . . Are there any tricks to bleed the brakes on this homebuilt?
Four master cylinders, one on each pedal, running to two 'T's, where a
single tube continues to each wing. Thinking of using a vacumn pump, to
pull the fluid down to the caliper.
Also, can anyone reccommend a good radio service shop in the Northwest?

[Orval Fairbairn[_2_]]

In article >,
"Pintlar" > wrote:

> Marchetti Sportster...
> . . . Are there any tricks to bleed the brakes on this homebuilt?
> Four master cylinders, one on each pedal, running to two 'T's, where a
> single tube continues to each wing. Thinking of using a vacumn pump, to
> pull the fluid down to the caliper.
> Also, can anyone reccommend a good radio service shop in the Northwest?

I was taught ALWAYS to bleed aircraft brakes from the wheel UP.

A simple pump-type oil can with a length of plastic tubing can serve
well as a bleed tool. Just make sure that it has a big enough reservoir
and that there is no air in the line.

Brake bleeding can be pretty messy and a two-man operation.

1. Pump the fluid into the tubing, leaving no air bubbles.
2. Attach the tubing to the bleed valve on the wheel cylinder.
3. Have assistant at the appropriate rudder pedal ready, with a drip
container, to open the master cylinder.
4. After assistant has opened the master cylinder, open the wheel
cylinder and pump until assistant sees only fluid and no air.
5. Close wheel valve; have assistant close the master cylinder valve.

6. Repeat #3-#5 for any other rudder pedal cylinders on that wheel.

7. Repeat #1-#6 for the opposite gear.

--
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[[email protected]]

On Nov 3, 5:01*pm, "Pintlar" > wrote:
> Marchetti Sportster...
> . . . Are there any tricks to bleed the brakes on this homebuilt?
> Four master cylinders, one on each pedal, running to two 'T's, *where a
> single tube continues to each wing. *Thinking of *using a vacumn pump, to
> pull the fluid down to the caliper.
> Also, can anyone reccommend a good radio service shop in the Northwest?

Reverse bleed .... from the brakes into the master cylinders? Works
on lots of brake systems.
=====================
Leon McAtee

[[email protected]]

On Nov 4, 8:03*am, "Pintlar" > wrote:
> *I am assuming
> this piston would have a reed type (ball type?) valve built into it so the
> fluid could only go one way, towards the caliper.

Your assumption may be incorrect.

Most master cylinders I've worked with have a simple bypass port
drilled just below the rest position of the piston for fluid transfer
by gravity from the reservoir. A millimeter or 2 of movement blocks
off this port during use. If the brake cylinder has been installed
with the piston already compressed then this port is covered and fluid
will not pass from the cylinder to the reservoir, acting like a one
way valve of sorts. This feature is handy when working on the wheel
end of the system to prevent loss of fluid. Just depress the master
cylinder enough to cover that port and then you can remove downstream
components and the fluid stays in the reservoir.

Some brake systems do have check valves, to retain residual pressure
in the lines, but these are normally installed down stream of the
master cylinder.
===================
Leon McAtee

[Jeff Peterson]

I tried the "pump from the bottom with an oil can" bit and made huge
mess.
Couldn't seem to get the fluid to pass through the cylinders.
It did however leak at the bleeder. puddles. profanity.

So, I tried a new (to me) approach. My Lancair
has a reservoir shared by the right and left sides.

It has two cylinders each side, in series.

The fill hole at the top of the reservoir has an 1/8 inch NPT thread,
normally a plug with a small hole goes there.

I took out the plug and put in an NPT-to-hose-nipple, and connected
a vacuum pump via tygon tubing.

The brake plumbing inside the cockpit is "nylaflow" tubing which is
translucent, so I could
see bubbles vs red brake fluid.

I turned on the pump, and watched the bubbles grow 100 times.
The brake fluid does not expand or boil.

Most of the greatly expanded air made it to the reservoir, bubbled up
and went into the pump.

With vacuum applied the calipers open about 1/4 inch.

Since the motion of the bubbles eventually stopped
(1 min) I know there was no leak in the system. After the bubble
stopped moving I let air back in,
watched the few remaining bubbles shrink, and
pumped the peddles to push the calipers back into position.

Repeated this process maybe 5 times. Pedals very firm now. Not a
drop of fluid on the floor.
Topped up the reservoir at the end. Process takes maybe 15 min.

I think I will now try the same trick on the landing gear hydraulic
system.

-Jeff

[Dana M. Hague[_2_]]

On my Kolb (Freebird calipers, Hegar master cylinders, no reservoir),
I attach tubing to the bleeder screw on the caliper which runs up to a
funnel (made from a 1 liter soda bottle). I fill the funnel with
brake fluid and hang it above the level of the master cylinders (let
fluid run down to fill the tubing until it's full before attaching it
to the bleeder screws on the calipers), open the bleeder screws at
both ends, and go do something else until bubbles stop coming out the
cylinder bleeder screws. No pumps required.

-Dana

On Tue, 3 Nov 2009 20:20:54 -0800 (PST), "
> wrote:

>On Nov 3, 5:01*pm, "Pintlar" > wrote:
>> Marchetti Sportster...
>> . . . Are there any tricks to bleed the brakes on this homebuilt?
>> Four master cylinders, one on each pedal, running to two 'T's, *where a
>> single tube continues to each wing. *Thinking of *using a vacumn pump, to
>> pull the fluid down to the caliper.
>> Also, can anyone reccommend a good radio service shop in the Northwest?
>
>Reverse bleed .... from the brakes into the master cylinders? Works
>on lots of brake systems.
>=====================
>Leon McAtee

--
I don't trust a government I can't shoot back at.

[Orval Fairbairn[_2_]]

In article >,
brian whatcott > wrote:

> Orval Fairbairn wrote:
>
> > I was taught ALWAYS to bleed aircraft brakes from the wheel UP.
> >
> > A simple pump-type oil can with a length of plastic tubing can serve
> > well as a bleed tool. Just make sure that it has a big enough reservoir
> > and that there is no air in the line.
> >
> > Brake bleeding can be pretty messy and a two-man operation.
> >
> > 1. Pump the fluid into the tubing, leaving no air bubbles.
> > 2. Attach the tubing to the bleed valve on the wheel cylinder.
> > 3. Have assistant at the appropriate rudder pedal ready, with a drip
> > container, to open the master cylinder.
> > 4. After assistant has opened the master cylinder, open the wheel
> > cylinder and pump until assistant sees only fluid and no air.
> > 5. Close wheel valve; have assistant close the master cylinder valve.
> >
> > 6. Repeat #3-#5 for any other rudder pedal cylinders on that wheel.
> >
> > 7. Repeat #1-#6 for the opposite gear.
> >
>
> As it happens, I had the day off, so today I headed over to an A&P not
> far away with a main tire for fitting. They packed the bearing, replaced
> the brake pads, and retracted the slave cylinder.
> When it came time to go, I pumped the pedal, but the brake action did
> not go hard.
> So I taxied back, and they added brake fluid using Orval's recipe.
> THEN the pedals came up firm....
>
> Brian W

You should not have needed additional fluid. When you remove a main
wheel, part of the process is to expand the calipers physically. When
everything is done, all you should have to do is press the brakes a
couple of times to get a firm pedal, since, theoretically, no fluid has
left the system, unless somebody disconnected a brake line during the
process.

--
Remove _'s from email address to talk to me.

[Brian Whatcott]

Orval Fairbairn wrote:

> I was taught ALWAYS to bleed aircraft brakes from the wheel UP.
>
> A simple pump-type oil can with a length of plastic tubing can serve
> well as a bleed tool. Just make sure that it has a big enough reservoir
> and that there is no air in the line.
>
> Brake bleeding can be pretty messy and a two-man operation.
>
> 1. Pump the fluid into the tubing, leaving no air bubbles.
> 2. Attach the tubing to the bleed valve on the wheel cylinder.
> 3. Have assistant at the appropriate rudder pedal ready, with a drip
> container, to open the master cylinder.
> 4. After assistant has opened the master cylinder, open the wheel
> cylinder and pump until assistant sees only fluid and no air.
> 5. Close wheel valve; have assistant close the master cylinder valve.
>
> 6. Repeat #3-#5 for any other rudder pedal cylinders on that wheel.
>
> 7. Repeat #1-#6 for the opposite gear.
>

As it happens, I had the day off, so today I headed over to an A&P not
far away with a main tire for fitting. They packed the bearing, replaced
the brake pads, and retracted the slave cylinder.
When it came time to go, I pumped the pedal, but the brake action did
not go hard.
So I taxied back, and they added brake fluid using Orval's recipe.
THEN the pedals came up firm....

Brian W

[Brian Whatcott]

Orval Fairbairn wrote:
> In article >,
> brian whatcott > wrote:
>
>> Orval Fairbairn wrote:
>>
>>> I was taught ALWAYS to bleed aircraft brakes from the wheel UP.
>>>
>>> A simple pump-type oil can with a length of plastic tubing can serve
>>> well as a bleed tool. Just make sure that it has a big enough reservoir
>>> and that there is no air in the line.
>>>
>>> Brake bleeding can be pretty messy and a two-man operation.
>>>
>>> 1. Pump the fluid into the tubing, leaving no air bubbles.
>>> 2. Attach the tubing to the bleed valve on the wheel cylinder.
>>> 3. Have assistant at the appropriate rudder pedal ready, with a drip
>>> container, to open the master cylinder.
>>> 4. After assistant has opened the master cylinder, open the wheel
>>> cylinder and pump until assistant sees only fluid and no air.
>>> 5. Close wheel valve; have assistant close the master cylinder valve.
>>>
>>> 6. Repeat #3-#5 for any other rudder pedal cylinders on that wheel.
>>>
>>> 7. Repeat #1-#6 for the opposite gear.
>>>
>> As it happens, I had the day off, so today I headed over to an A&P not
>> far away with a main tire for fitting. They packed the bearing, replaced
>> the brake pads, and retracted the slave cylinder.
>> When it came time to go, I pumped the pedal, but the brake action did
>> not go hard.
>> So I taxied back, and they added brake fluid using Orval's recipe.
>> THEN the pedals came up firm....
>>
>> Brian W
>
> You should not have needed additional fluid. When you remove a main
> wheel, part of the process is to expand the calipers physically. When
> everything is done, all you should have to do is press the brakes a
> couple of times to get a firm pedal, since, theoretically, no fluid has
> left the system, unless somebody disconnected a brake line during the
> process.
>


That's what the A&P said too. But this was a new acquisition, whose
maintenance state was a (comparatively) unknown quantity. In fact, I
had not picked up on the relatively long rudder pedal travel earlier,
until I lost action.

Brian W