Brake issue M20J

[bmcconnaha]

Last night I had something odd happen with my left brake.  I left Three Forks, Montana after a quick turn there.  No issue with the brakes.  Very cold OAT.  Around zero degrees Fahrenheit. The weather was deteriorating, and it was getting dark, so I landed in Missoula Montana for the night.  When I exited the runway, I had a very apparent pull to the left.  Definitely a sticky brake.  I slowly taxied to the FBO.  They put me in a heated hangar overnight.  On getting to the plane this morning, the caliper was still dragging pretty good.  I pumped the brakes on both sides again, and it freed right up.  Any idea what to look for? Can taxi and take off at an airport that has some loose and compacted snow get snow with debris in the guide and jam it up? 

Thanks, 

             Bryan 

[Yetti]

yes.  Snow and stuff can jam up the calipers.   The calipers slide along rails and should be cleaned and lightly lubed.

[bmcconnaha]

18 minutes ago, Yetti said:

yes.  Snow and stuff can jam up the calipers.   The calipers slide along rails and should be cleaned and lightly lubed.

I saw graphite lube if I remember correctly was what was specified in the maintenance manual.  Ill pull the inner gear doors and have a look.  Would you bleed the brakes while you're there? Or, is that opening a can of worms? 

[N201MKTurbo]

I’ve had water freeze the disk to the calipers so you land with a frozen wheel. They always skid for a while then break loose. Ice and slush can cause all kind of weird things happen in the winter. If I have a heater like a torpedo heater or an engine pre heater, I will point it at the brakes for a bit to heat them  up and dry them off. 

[Nippernaper]

I once had a similar issue. It was actually the brake cylinder catching on, as I recall, the fuel boost pump, when I was depressing the brakes to set the parking brake. This would effectively keep the left brake engaged. Might be worth a look if it happens again.


Sent from my iPhone using Tapatalk

[bmcconnaha]

56 minutes ago, N201MKTurbo said:

I’ve had water freeze the disk to the calipers so you land with a frozen wheel. They always skid for a while then break loose. Ice and slush can cause all kind of weird things happen in the winter. If I have a heater like a torpedo heater or an engine pre heater, I will point it at the brakes for a bit to heat them  up and dry them off. 

That’s an idea, I’ll give that a try also when it’s this cold.  

[Yetti]

1 hour ago, bmcconnaha said:

I saw graphite lube if I remember correctly was what was specified in the maintenance manual.  Ill pull the inner gear doors and have a look.  Would you bleed the brakes while you're there? Or, is that opening a can of worms? 

No need to bleed.   unless of course you have a soft pedal, but it seems more like a gunk preventing the calipers from sliding

[RobertGary1]

2 hours ago, Yetti said:

No need to bleed.   unless of course you have a soft pedal, but it seems more like a gunk preventing the calipers from sliding

The fluid turns to gel and can cause this. Bleed the brakes down and see if you get jello out. Don’t bleed up and push the jello into into master 

[bmcconnaha]

1 hour ago, RobertGary1 said:

The fluid turns to gel and can cause this. Bleed the brakes down and see if you get jello out. Don’t bleed up and push the jello into into master 

Ok, I’ll ask my a&p about that.  Thank you 

[Guest]

9 minutes ago, bmcconnaha said:

Ok, I’ll ask my a&p about that.  Thank you 

Connect a pressure pot with Mil H 5606 hydraulic oil to the top of the reservoir with about 5 psi, got to the wheel cylinders one at a time, open the bleeder screw with a 1/4” 6 point wrench, open the bleeder and let it run until you get clean oil running out.  Gelled fluid usually builds in the wheel cylinder and lower hose.

Clarence

[bmcconnaha]

12 minutes ago, M20Doc said:

Connect a pressure pot with Mil H 5606 hydraulic oil to the top of the reservoir with about 5 psi, got to the wheel cylinders one at a time, open the bleeder screw with a 1/4” 6 point wrench, open the bleeder and let it run until you get clean oil running out.  Gelled fluid usually builds in the wheel cylinder and lower hose.

Clarence

Seems easy enough, thank you 

[Yetti]

3 hours ago, RobertGary1 said:

The fluid turns to gel and can cause this. Bleed the brakes down and see if you get jello out. Don’t bleed up and push the jello into into master 

If it is old.   5606 is good down to -65F.    Every 5 years the fluid should be replaced.  Check the logs to see when it was done last.

[bmcconnaha]

1 minute ago, Yetti said:

If it is old.   5606 is good down to -65F.    Every 5 years the fluid should be replaced.  Check the logs to see when it was done last.

I don’t recall ever seeing it replaced in the logs.  Plane is a 1990

[Yetti]

2 minutes ago, bmcconnaha said:

I don’t recall ever seeing it replaced in the logs.  Plane is a 1990

If that is the case then the lower hoses should be done also.   Mine broke in half when I bent them.

[EricJ]

The Royco 782 and Aeroshell 31 synthetic brake fluids are approved for use in Mooneys and are miscible with 5606 (i.e., you can mix them, so you don't have to flush all the old stuff if you don't want).   I suspect they won't turn to goo like 5606 does.   I've bought a decent supply of it but have not yet changed it since my brakes have been working fine for a while, but as soon as it needs fluid or a flush this stuff is going to go in.

 

[bmcconnaha]

2 hours ago, EricJ said:

The Royco 782 and Aeroshell 31 synthetic brake fluids are approved for use in Mooneys and are miscible with 5606 (i.e., you can mix them, so you don't have to flush all the old stuff if you don't want).   I suspect they won't turn to goo like 5606 does.   I've bought a decent supply of it but have not yet changed it since my brakes have been working fine for a while, but as soon as it needs fluid or a flush this stuff is going to go in.

 

Awesome, thank you.  I’m going to replace hoses, so it makes sense to flush it with the new stuff 

[RobertGary1]

5 hours ago, bmcconnaha said:

Awesome, thank you.  I’m going to replace hoses, so it makes sense to flush it with the new stuff 

Flush goo down and air up. So you’ll want to go both ways. Getting the air out is a whole science itself.