Hydraulic brake problems

[Dick[_3_]]

Hydraulic brake problems. The disc brake on my D2b has provided only
very limited stopping ability for a year or so now. When attempting
to put on the brakes the brake handle moves all the way back to the
stick grip. We have repeatedly attempted to eliminate air in the
system by pumping .4 fluid up through the wheel cylinder drain
nipple. We have sucked the system dry by vacuum applied, also to the
same nipple. We have checked the nipple itself for blockage. We
replaced the master cylinder. We checked the cable to make sure there
was no slack yet the abbreviated handle plunger was virtually in
contact with the piston in the master cylinder and the master cylinder
piston was moving. Nothing seems to make any difference. IT

[Dan[_6_]]

On Mar 27, 9:34*am, Dick > wrote:
> Hydraulic brake problems. *The disc brake on my D2b has provided only
> very limited stopping ability for a year or so now. *When attempting
> to put on the brakes the brake handle moves all the way back to the
> stick grip. *We have repeatedly attempted to eliminate air in the
> system by pumping .4 fluid up through the wheel cylinder drain
> nipple. *We have sucked the system dry by vacuum applied, also to the
> same nipple. *We have checked the nipple itself for blockage. *We
> replaced the master cylinder. *We checked the cable to make sure there
> was no slack yet the abbreviated handle plunger was virtually in
> contact with the piston in the master cylinder and the master cylinder
> piston was moving. *Nothing seems to make any difference. *IT

Sounds like you are doing everything right.
I assume you checked for wear of the pads? Easy to replace them and
always a good idea.
Also it is easy to replace the O-ring on the brake master cylinder.
However you would see seepage atounf the Master cylinder if it is
bad. I change them every few years because they do get old and hard.

good luck,
Dan
WO

[sisu1a]

> We checked the cable to make sure there
> was no slack yet the abbreviated handle plunger was virtually in
> contact with the piston in the master cylinder and the master cylinder
> piston was moving. *Nothing seems to make any difference. *

In addition to pad wear, discs get thinned over time as well. Make
sure the disc and pads are up to spec'd thicknesses. It is possible
the combo of both can run the piston out of useful travel. Also verify
the cable is transmitting full force, a frayed/worn out cable can have
enough strength to plunge the piston, but so much elasticity that it
won't do it with much force, especially if it's one of those wussy
bicycle cables and not the stout Boden (motorcycle) variety.

-Paul

[glidergeek]

On Mar 27, 10:58*am, sisu1a > wrote:
> > We checked the cable to make sure there
> > was no slack yet the abbreviated handle plunger was virtually in
> > contact with the piston in the master cylinder and the master cylinder
> > piston was moving. *Nothing seems to make any difference. *
>
> In addition to pad wear, discs get thinned over time as well. Make
> sure the disc and pads are up to spec'd thicknesses. It is possible
> the combo of both can run the piston out of useful travel. Also verify
> the cable is transmitting full force, a frayed/worn out cable can have
> enough strength to plunge the piston, but so much elasticity that it
> won't do it with much force, especially if it's one of those wussy
> bicycle cables and not the stout Boden (motorcycle) variety.
>
> -Paul

Look at your caliper real close to verify that your line comes out the
very top of the piston cavity. If not you will need to make the line
as high as possible or even remove it and position it so the line is
high and then bleed again.

[Mike the Strike]

On Mar 27, 2:02*pm, glidergeek > wrote:
> On Mar 27, 10:58*am, sisu1a > wrote:
>
> > > We checked the cable to make sure there
> > > was no slack yet the abbreviated handle plunger was virtually in
> > > contact with the piston in the master cylinder and the master cylinder
> > > piston was moving. *Nothing seems to make any difference. *
>
> > In addition to pad wear, discs get thinned over time as well. Make
> > sure the disc and pads are up to spec'd thicknesses. It is possible
> > the combo of both can run the piston out of useful travel. Also verify
> > the cable is transmitting full force, a frayed/worn out cable can have
> > enough strength to plunge the piston, but so much elasticity that it
> > won't do it with much force, especially if it's one of those wussy
> > bicycle cables and not the stout Boden (motorcycle) variety.
>
> > -Paul
>
> Look at your caliper real close to verify that your line comes out the
> very top of the piston cavity. If not you will need to make the line
> as high as possible or even remove it and position it so the line is
> high and then bleed again.

The hydraulic brake failed on my Discus 2 also a year or so ago and we
finally installed a repair kit on the master cylinder. We had lost
one of the o-rings and the fix worked perfectly. Bleeding the system
wasn't easy and we only got success after feeding fluid under pressure
from the slave.

i wonder if you effectively bled the system after installing the new
master cylinder?

Mike

[weersch[_2_]]

Here my experience on my V2C 3U.
2 years ago, my brake was very tight and would respond immediately
with no slack.
Last season, I noticed brake fluid dripping from a drain hole in the
bottom of the fuselage.
Also my brake action deteriorated gradually.
I had not replaced the brake fluid (like I never do on my cars either)
and the fluid had gummed and was leaking around the master brake
cylinder. I replaced the original 20mm piston Magura master cylinder
with a new 16mm piston unit (mounted standard on BMW motorcycles) .
After extensive bleeding as described above, I still could not regain
real pressure.
(I realize that the smaller master piston does require more travel.)
However, at further inspection, I noticed that the brake pad on the
Cleveland caliper would withdraw upon release of the brake handle.
In other words, the caliper does not rest tight and at each brake
action fluid volume needs to be filled to bring the brake pads tight,
before brake pressure can be build up.
I decide to completely disassemble the Cleveland assembly to check for
gumming up and for overhaul.
Turns out there is hardly anything in the Cleveland assembly. Just one
standard O-ring.
New O-rings ordered. Caliper disassembled. Piston carefully pushed out
with a little airpressure from a small 12 V tire compressor.
It turned out that the aluminum caliper and piston had been corroded
substantially.
I presume from condensation moisture from high altitude flying and
mixing with the hydraulic fluid.
I lightly sanded, with 800 sand paper, the corroded section, where the
O-ring sits. Installed the new O-ring and re-assembled.
After again extensive bleeding (upwards from the caliper to the
reservoir), I now have pressure.
I still need to test fly to see how well the overhaul works.
I am not yet sure if this has resolve all problems as I now have
substantially more "squeeze" than before.
But as mentioned, this could be partly due to the smaller master
piston, which would give more throw but also more force/pressure.
Summarizing: My first problem was the leaking master cylinder. After
that next problem was piston in the Cleveland caliper retracting upon
brake lever release (instead of taking new fluid from the reservoir).
I am still not sure if this retracting is a problem of the new master
cylinder or a problem of the corroded Cleveland brake caliper.
3U

[Brian Liddiard]

Hi Dick.

If you have checked everything, check it again! I think Mike is going in
the right direction and you still have air in the system.
If everything is ok then try this when bleeding the system.

With two people pump the handle to get maximum pressure, your assistant
then opens the bleed nipple forcing the fluid out, hold the leaver until
the nipple is closed then slowly release the leaver, wait 30 seconds then
repeat. Hopefully you will feel it improving after 4 or 5 pumps and don't
forget to top up as you do this.

Regards

Brian

[Andy[_1_]]

On Mar 27, 9:34*am, Dick > wrote:

>We have sucked the system dry by vacuum applied, also to the
>same nipple.

I assume you actually didn't mean that since sucking the system dry
ensures that it is totally filled with air unless you used a high
vacuum pump.

Getting a high flow rate using either suction or pressure usually
works but you need a fluid reservoir large enough to sustain the
flow. My PA28-180 has 5 master cylinders and 2 slave cylinders and is
a real bitch to bleed after the system has been opened. I used a pump
up garden sprayer to feed fluid to the caliper bleed nipples and used
a large bottle to catch the overflow from the reservoir.

So far I've had no problem with the hydraulic brake on my 28 so no
experience with that yet.

Andy

[Eric Greenwell[_4_]]

On 3/28/2011 1:46 AM, weersch wrote:
>
> But as mentioned, this could be partly due to the smaller master
> piston, which would give more throw but also more force/pressure.
> Summarizing: My first problem was the leaking master cylinder. After
> that next problem was piston in the Cleveland caliper retracting upon
> brake lever release (instead of taking new fluid from the reservoir).
> I am still not sure if this retracting is a problem of the new master
> cylinder or a problem of the corroded Cleveland brake caliper.

I had a similar problem with my Cleveland brake system on my ASH 26E. It
worked fine for years, but one day it was very "spongy" after rigging. I
loosened the cap on the fluid reservoir, and in just two brake
applications, it was working fine. I cleaned the cap and the vent in it,
and have had no further problems in the seven years since then.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
you need to know tinyurl.com/yfs7tnz

[Andy[_1_]]

On Mar 27, 10:58*am, sisu1a > wrote:


>It is possible the combo of both can run the piston out of useful travel.

Don't see how that is possible. Hydraulic disk brake systems are self
compensating for wear. As the pads and disk wear the system fluid
volume increases and fluid transfers from the master cylinder
reservoir when the piston is in the retracted position. There is no
limit on the piston travel of a Cleveland caliper. It just keeps
going until it is ejected from the O ring seal.

Andy

[Grider Pirate]

On Mar 28, 7:37*am, Andy > wrote:
> On Mar 27, 9:34*am, Dick > wrote:
>
> >We have sucked the system dry by vacuum applied, also to the
> >same nipple.
>
> I assume you actually didn't mean that since sucking the system dry
> ensures that it is totally filled with air unless you used a high
> vacuum pump.
>
> Getting a high flow rate using either suction or pressure usually
> works but you need a fluid reservoir large enough to sustain the
> flow. *My PA28-180 has 5 master cylinders and 2 slave cylinders and is
> a real bitch to bleed after the system has been opened. *I used a pump
> up garden sprayer to feed fluid to the caliper bleed nipples and used
> a large bottle to catch the overflow from the reservoir.
>
> So far I've had no problem with the hydraulic brake on my 28 so no
> experience with that yet.
>
> Andy

3U hit the nail on the head for 'cause'. Automotive brake fluid, used
as we do (infrequently, by automotive standards) really needs to be
fully cycled out annually to prevent excessive water absorbtion and
the attendant corrosion. I've been changing out brake fluild in my
cars on a bi-annual basis since the 70's, and haven't had to replace
or rebuild a caliper, slave, or master cylinder since that time (and I
tend to keep vehicles for decades).

[sisu1a]

> Don't see how that is possible. *Hydraulic disk brake systems are self
> compensating for wear. *

So long at the reservoir is vented. Most use a bleeder cap (usually
just a pinhole in the fill plug), but not all. Ones without bleeder
caps need to be 'burped' every so often since it is not allowing air
into the reservoir (above the fluid) to allow the displacement needed
for the pads to self adjust as they wear.

-Paul

[Eric Greenwell[_4_]]

On 3/28/2011 7:50 AM, Grider Pirate wrote:
> On Mar 28, 7:37 am, > wrote:
>> On Mar 27, 9:34 am, > wrote:
>>
>>> We have sucked the system dry by vacuum applied, also to the
>>> same nipple.
>>
>> I assume you actually didn't mean that since sucking the system dry
>> ensures that it is totally filled with air unless you used a high
>> vacuum pump.
>>
>> Getting a high flow rate using either suction or pressure usually
>> works but you need a fluid reservoir large enough to sustain the
>> flow. My PA28-180 has 5 master cylinders and 2 slave cylinders and is
>> a real bitch to bleed after the system has been opened. I used a pump
>> up garden sprayer to feed fluid to the caliper bleed nipples and used
>> a large bottle to catch the overflow from the reservoir.
>>
>> So far I've had no problem with the hydraulic brake on my 28 so no
>> experience with that yet.
>>
>> Andy
>
> 3U hit the nail on the head for 'cause'. Automotive brake fluid, used
> as we do (infrequently, by automotive standards) really needs to be
> fully cycled out annually to prevent excessive water absorbtion and
> the attendant corrosion.

This sounds like you think all our Cleveland brake systems use
automotive brake fluid. Just in case you or someone else thinks that,
let me mention my ASH 26E maintenance manual is adamant "that only
MINERAL OIL BASED" brake fluid is used in it's Cleveland system, and
definitely NOT automotive fluid, which "will quickly destroy gaskets and
hoses".

So, always check your manual first.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl

[John Sullivan]

I had the same problem with my Ventus and it took me a long
time to figure it out. Eventually i discovered that the plunger
which enters the master cylinder was dry and actually frozen in
position so that no matter what i did to the bowdan cable,
actuating lever, caliper had no effect. Mine was so tight I
actually broke a hand lever trying to stop once! Its a very
simple fix. Remove the master cylinder, slightly withdraw
actuating plunger, clean it up and lube it with Dow Corning or
similar silicone grease. That is the fix! Then make sure you
lube that bugger each annual. Please post if it works!

John Sullivan, UFO

[Andy[_1_]]

On Mar 28, 12:54*pm, Eric Greenwell > wrote:
> On 3/28/2011 7:50 AM, Grider Pirate wrote:
>
>
>
> > On Mar 28, 7:37 am, > *wrote:
> >> On Mar 27, 9:34 am, > *wrote:
>
> >>> We have sucked the system dry by vacuum applied, also to the
> >>> same nipple.
>
> >> I assume you actually didn't mean that since sucking the system dry
> >> ensures that it is totally filled with air unless you used a high
> >> vacuum pump.
>
> >> Getting a high flow rate using either suction or pressure usually
> >> works but you need a fluid reservoir large enough to sustain the
> >> flow. *My PA28-180 has 5 master cylinders and 2 slave cylinders and is
> >> a real bitch to bleed after the system has been opened. *I used a pump
> >> up garden sprayer to feed fluid to the caliper bleed nipples and used
> >> a large bottle to catch the overflow from the reservoir.
>
> >> So far I've had no problem with the hydraulic brake on my 28 so no
> >> experience with that yet.
>
> >> Andy
>
> > 3U hit the nail on the head for 'cause'. Automotive brake fluid, used
> > as we do (infrequently, by automotive standards) really needs to be
> > fully cycled out annually to prevent excessive water absorbtion and
> > the attendant corrosion.
>
> This sounds like you think all our Cleveland brake systems use
> automotive brake fluid. Just in case you or someone else thinks that,
> let me mention my ASH 26E maintenance manual is adamant "that only
> MINERAL OIL BASED" brake fluid is used in it's Cleveland system, and
> definitely NOT automotive fluid, which "will quickly destroy gaskets and
> hoses".
>
> So, always check your manual first.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
> email me)
> - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarmhttp://tinyurl.com/yb3xywl

Same for the ASW-28. I know some glider manufacturers chose to abuse
a perfectly good aircraft braking system by use of auto style brake
fluids but not all of them did.

Andy

[bumper[_4_]]

The Cleveland caliper was originally intended for use with Mil Spec
5606 brake fluid (the red petroleum based stuff). The caliper piston
was plain aluminum and the O-ring and seals Buna-N.

When using automotive brake fluid, as some glider manufacturers do, O-
rings and seals are changed to EPDM rubber. The hygroscopic nature of
automotive brake fluid can cause corrosion of the caliper piston and
bore. Later Cleveland pistons (late 90's ?)were anodized* (relatively
easy to do aftermarket as well) and this, along with brass lining the
caliper bore, eleminates further problems. http://www.brakecylinder.com/
does a good job brass lining bores.

*Easy to check to see if your piston is anodized. Touch the leads of
an ohm meter to the piston. If it's anodized, it won't conduct as the
anodize (aluminum oxide) layer is an insulator.

As someone previously mentioned, it's important to insure the caliper
hose inlet is at the top while bleeding. If you have to dismount the
caliper, use a C-clamp or similar to hold piston in while bleeding. I
recommend a pressure pot (one can be cobbled together from a small
garden sprayer) to get a good robust flow going. This will remove air
trapped in any high spots in the plumbing.

bumper