Brake Cylinder Problem

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Re: Brake Cylinder Problem

Postby edbooth » Fri Mar 27, 2020 4:46 pm

cessna170bdriver wrote:Each brake pedal on the new-to-us 170B occasionally goes to the floor then pumps right back up. This particular airplane has McCauley brakes, but there is no leakage at the wheel cylinders. I’m assuming I need new piston o-rings and lock-o-seals in the master cylinders. I was looking on Aircraft Spruce and they have a kit that includes 3 o-rings, a lock-o-seal, and a “tube fitting gasket”. The illustrations in both the 170B IPC and the 100 series service manual only show a piston o-ring and lock-o-seal. Are the other parts just to make the kit cover more models, or is there something I’m missing on the illustrations?

Also, is there a better source than ACS?


Sometime ago I had a right brake pedal that would go to the floor, usually at a most inopportune time. Finally replaced the lock-O-Seal..... No more problems. Was easy fix, just unscrew the top cap and pull the guts out, replace parts and slide back in.
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Re: Brake Cylinder Problem

Postby cessna170bdriver » Fri Mar 27, 2020 5:07 pm

Bruce Fenstermacher wrote:Can’t answer your question but it is your lock-o-seal that is not sealing to allow the cylinder to build pressure. I fixed mine ordering just the oil ring and lock-o-seal from the IPC.


Thanks Bruce, where did you order?
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Re: Brake Cylinder Problem

Postby cessna170bdriver » Fri Mar 27, 2020 5:13 pm

edbooth wrote:...

Sometime ago I had a right brake pedal that would go to the floor, usually at a most inopportune time. Finally replaced the lock-O-Seal..... No more problems. Was easy fix, just unscrew the top cap and pull the guts out, replace parts and slide back in.


Thanks Ed, That’s pretty much what I guessed from looking at the IPC and service manual. It looks like the hardest part will be working behind the pedal to remove and replace the cotter pin at the top of the piston rod.
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Re: Brake Cylinder Problem

Postby cessna170bdriver » Fri Mar 27, 2020 7:26 pm

Is this the correct part for the lock-o-seal?
https://www.aircraftspruce.com/catalog/ ... -14698.php
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Re: Brake Cylinder Problem

Postby Bruce Fenstermacher » Fri Mar 27, 2020 10:32 pm

800-0001-6-2.jpg


This is what they actually look like.800-0001-6 is the new number The old number was 200AC-6

Can't say where I bought them. Probably Spruce
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Re: Brake Cylinder Problem

Postby edbooth » Sat Mar 28, 2020 1:52 pm

cessna170bdriver wrote:
edbooth wrote:...

Sometime ago I had a right brake pedal that would go to the floor, usually at a most inopportune time. Finally replaced the lock-O-Seal..... No more problems. Was easy fix, just unscrew the top cap and pull the guts out, replace parts and slide back in.


Thanks Ed, That’s pretty much what I guessed from looking at the IPC and service manual. It looks like the hardest part will be working behind the pedal to remove and replace the cotter pin at the top of the piston rod.


I think that was the hardest part Miles. To make it a little easier, took out the front seat so I could lay on my stomach and get to everything.
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Re: Brake Cylinder Problem

Postby DaveF » Sat Mar 28, 2020 5:57 pm

edbooth wrote:
cessna170bdriver wrote:
edbooth wrote:...

Sometime ago I had a right brake pedal that would go to the floor, usually at a most inopportune time. Finally replaced the lock-O-Seal..... No more problems. Was easy fix, just unscrew the top cap and pull the guts out, replace parts and slide back in.


Thanks Ed, That’s pretty much what I guessed from looking at the IPC and service manual. It looks like the hardest part will be working behind the pedal to remove and replace the cotter pin at the top of the piston rod.


I think that was the hardest part Miles. To make it a little easier, took out the front seat so I could lay on my stomach and get to everything.

The cotter pin at the bottom of the cylinder is worse!
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Re: Brake Cylinder Problem

Postby gahorn » Sat Mar 28, 2020 6:06 pm

Ed’s idea of laying on one’s stomach is the hard part for me. :lol:
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Re: Brake Cylinder Problem

Postby ghostflyer » Sun Mar 29, 2020 2:49 am

When that lock-out-seal is replaced or inspected make sure that the correct clearance is adjusted for that lock-out -seal .
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Re: Brake Cylinder Problem

Postby edbooth » Sun Mar 29, 2020 1:52 pm

gahorn wrote:Ed’s idea of laying on one’s stomach is the hard part for me. :lol:


George, I forgot some folks may be anatomically challenged.... :lol:
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Re: Brake Cylinder Problem

Postby edbooth » Sun Mar 29, 2020 2:08 pm

Dave, you don't have to take the lower attach point loose for this. Just take the shaft loose from the rudder/brake pedal, unscrew the assembly from the top of the cylinder and pull it out. If you still have that dorky parking brake, this should be disconnected for ease of repair. Install the new repair parts and slide it back in. (Put a rag around the cylinder so brake fluid don't run down where you don't want it)
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Re: Brake Cylinder Problem

Postby gahorn » Sun Mar 29, 2020 2:35 pm

When disassembling any items,...COUNT the number of turns (threads) being disassembled so that you can return them to the same position during reassembly.
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Re: Brake Cylinder Problem

Postby DaveF » Sun Mar 29, 2020 6:10 pm

edbooth wrote:Dave, you don't have to take the lower attach point loose for this. Just take the shaft loose from the rudder/brake pedal, unscrew the assembly from the top of the cylinder and pull it out. If you still have that dorky parking brake, this should be disconnected for ease of repair. Install the new repair parts and slide it back in. (Put a rag around the cylinder so brake fluid don't run down where you don't want it)

Ed, sorry, I didn't mean to suggest removing the cylinder for the work under discussion. I was just remembering the difficulty of removing the cotter pin on the clevis at the bottom attach point. I pulled it to replace the hoses and repair the brake cylinder attach bracket.
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Re: Brake Cylinder Problem

Postby edbooth » Mon Mar 30, 2020 12:35 am

DaveF wrote:
edbooth wrote:Dave, you don't have to take the lower attach point loose for this. Just take the shaft loose from the rudder/brake pedal, unscrew the assembly from the top of the cylinder and pull it out. If you still have that dorky parking brake, this should be disconnected for ease of repair. Install the new repair parts and slide it back in. (Put a rag around the cylinder so brake fluid don't run down where you don't want it)

Ed, sorry, I didn't mean to suggest removing the cylinder for the work under discussion. I was just remembering the difficulty of removing the cotter pin on the clevis at the bottom attach point. I pulled it to replace the hoses and repair the brake cylinder attach bracket.


Ok, no problem Dave. Just wanted to make sure you were not subjecting yourself to some un-needed torture. I went through that when I had to replace those mounting brackets.
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Re: Brake Cylinder Problem

Postby cessna170bdriver » Mon Mar 30, 2020 4:16 am

gahorn wrote:When disassembling any items,...COUNT the number of turns (threads) being disassembled so that you can return them to the same position during reassembly.


The clevis doesn’t have to be removed - all the parts come off the bottom of the piston rod. Per the service manual, the nut retaining the piston is tightened until you get 0.040” clearance between the bottom of the piston and the top of the lock-o-seal retainer.
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