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Stuck Parking Brake

wawrzynskivp

Well Known Member
I normally set the parking brake prior to engine start. This is a purpose built hydraulic valve that sets a check valve in place on both brake lines, then releases the check valves to release the brakes.

On my last start I noticed the right brake remained locked after I put the valve back in the release position. I wasn't going anywhere but in circles, so I shut down and cycled the valve a few times. I could hear the left side set and release, but the right side remained quietly locked. Then unfortunately the left side also began to remain quiet and then both brakes were locked.

I mounted my valve where I can actuate the valve lever itself, meaning it is not remoted with a cable.

So I was stuck blocking traffic until I could get the wheel pants off and loosen the hyd fittings at the brakes to release the pressure. The good news if any is that this was an engine warm up prior to my annual condition inspection so no disappointed passengers.

Anyone ever encountered this? Seems impossible but it was a very real nuisance.
 
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I normally set the parking brake prior to engine start. This is a purpose built hydraulic valve that sets a check valve in place on both brake lines, then releases the check valves to release the brakes.

On my last start I noticed the right brake remained locked after I put the valve back in the release position. I wasn't going anywhere but in circles, so I shut down and cycled the valve a few times. I could hear the left side set and release, but the right side remained quietly locked. Then unfortunately the left side also began to remain quiet and then both brakes were locked.

I mounted my valve where I can actuate the valve lever itself, meaning it is not remoted with a cable.

So I was stuck blocking traffic until I could get the wheel pants off and loosen the hyd fittings at the brakes to release the pressure. The good news if any is that this was an engine warm up prior to my annual condition inspection so no disappointed passengers.

Anyone ever encountered this? Seems impossible but it was a very real nuisance.
Have you tried pumping the brake after releasing. In most cases, it will release after pumping it once or twice.
 
Have you tried pumping the brake after releasing. In most cases, it will release after pumping it once or twice.

Yes, tried pumping, rocking the airplane back and forth by hand, resetting and releasing, all to no effect other than to get the other brake to also jam.

Just had dialogue with Matco and there is an issue with O-ring distortion. Apparently we are supposed to put pressure back on the brake pedals when we release the valve in order to keep from distorting internal O-rings. But they couldn't offer a failure mode to account for what I saw and asked for the valve to be returned to them.
 
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Duck

I had to put stronger Springs on my pedal release, the pedal on the Matco must be absolutely 100% up to release the brakes. Just one more thing to check?
 
I just rebuilt a matco valve that I had bought used a couple of months ago.

The lever on the side rotates a camshaft that pushes the individual valve pistons one way, then when you rotate the lever the other way, The internal springs push the pistons back up to keep them nestled up to the cam lobes.

seems reasonable that a stuck o-ring could bind up the works so that the spring couldn't do it's thing.

If it were me, a $20 rebuild kit would be where I would start.
 
I don't have the parking brake but have the Matco brakes. Mine doesn't want to release on the right hand side after applying pressure on the pedals. Super annoying and my right hand wheel pants almost caught fire yesterday. So I'm also thinking deformed o-ring. Sounds like the culprit to me.
 
Viton

I have my parking brake installed but the system is not primed yet. Is there a way to switch out the o rings for Viton or some other material that wont deform? I would like to do this before I prime the system.
 
I don't have the parking brake but have the Matco brakes. Mine doesn't want to release on the right hand side after applying pressure on the pedals. Super annoying and my right hand wheel pants almost caught fire yesterday. So I'm also thinking deformed o-ring. Sounds like the culprit to me.

Maybe wrong but it sounds like the brake pedal is not releasing all the way. A very common problem and there is probably a hundred or more postings regarding this with several fixes suggested. Might try a search on the forums to get more info?
Try reaching down and pulling back on the brake pedals when you feel this drag. might surprise you
 
Maybe wrong but it sounds like the brake pedal is not releasing all the way. A very common problem and there is probably a hundred or more postings regarding this with several fixes suggested. Might try a search on the forums to get more info?
Try reaching down and pulling back on the brake pedals when you feel this drag. might surprise you

If you don't have the solid shaft upgrade for the brake pedal's pivot, and instead have the two bolts, one on either side, this is a possibility. We all changed the brake pedal pivot to a solid rod thru both pivots to prevent the pedals from not releasing. Others have also added helper springs from McMaster-Carr.
 
I just rebuilt a matco valve that I had bought used a couple of months ago.

The lever on the side rotates a camshaft that pushes the individual valve pistons one way, then when you rotate the lever the other way, The internal springs push the pistons back up to keep them nestled up to the cam lobes.

seems reasonable that a stuck o-ring could bind up the works so that the spring couldn't do it's thing.

If it were me, a $20 rebuild kit would be where I would start.

Thanks for the 'inside knowledge.' It sounds very much like what happened to me, and was hinted at by the rep at Matco. Using the 'balanced pressure' release method the parking brake valve has returned that valve to working normally.
 
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If you don't have the solid shaft upgrade for the brake pedal's pivot, and instead have the two bolts, one on either side, this is a possibility. We all changed the brake pedal pivot to a solid rod thru both pivots to prevent the pedals from not releasing. Others have also added helper springs from McMaster-Carr.

Thanks. Mine still have the two bolts on either side. I'll see about the upgrade.
 
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