Hydraulic brake problems

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).

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

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

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

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

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