Time for new brakes?

Chilito

Chilito

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Chilito
Hi, all.

Second post for this new owner. I appreciate all of your thoughts and suggestions so far.

According to the logs, my 150H hasn't had new pads/brake service in almost 200 hours, except for inspection during annual. Turning left off the runway today, it required pedal to the floor and required extremely slow speed. If I were going any faster, I could have been off the pavement. Right side braking action is good. The rudder turns fine, slightly more travel to full right than full left. I don't think it's steering rods, as they seem pretty tight.

Wondering if it's as simple as new pads/disc/etc, and suggestions for parts/install price I'm looking at.

Thanks,
Rob
 
You can visually inspect the linings and see if they need replacement. If the braking action is spongy or grabby, you may need to bleed it or check things for wear or corrosion. Will not likely be very expensive.
 
200 hours isn't much for brake linings unless you're in the habit of taxiing with the RPM at 1000 and dragging the brakes to control the speed. More likely you need some hydraulic work, like topping up the fluid in the master cylinders and maybe bleeding the air out of that left side. And I suspect that the rudder control system is out of rig, as the travels should be the same left and right. I frequently found Cessna rudder system out of rig, since mechanics often don't consult the maintenance manual and just fool with it. Proper rigging starts with the nosegear steering bungees, for instance.
 
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Doug Reid said:
A couple years ago, my left brake pedal went all the way to the floor on landing, but pumped back up firm. After checking for leaks...none found...I taxied around the ramp and got this to happen once again. Inside the brake master cylinder, there is a one way valve that allows fluid to return to the cylinder after braking, but is supposed to close when you apply pressure. There is a tiny o’ring on that valve..it was torn..allowing the brakes to work part of the time. If you do not find any leaks around the piston o’ring, or a hose leak, and you confirm there is adequate fluid and the brakes have been bled of air...check the brake cylinder.
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Doug Reid said:
A couple years ago, my left brake pedal went all the way to the floor on landing, but pumped back up firm. After checking for leaks...none found...I taxied around the ramp and got this to happen once again. Inside the brake master cylinder, there is a one way valve that allows fluid to return to the cylinder after braking, but is supposed to close when you apply pressure. There is a tiny o’ring on that valve..it was torn..allowing the brakes to work part of the time. If you do not find any leaks around the piston o’ring, or a hose leak, and you confirm there is adequate fluid and the brakes have been bled of air...check the brake cylinder.
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Here is what you are talking about.
There really isn't a valve, as the o'ring enters the cylinder it closes the system and as it travels down the cylinder it creates pressure to extend the brake cylinder pressing the pucks to the disks.
When the pedal is released the piston / o'ring is retracted from the cylinder, then any pressurized fluid is free to return to the reservoir.
 

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GeorgeC said:
You can visually inspect the linings and see if they need replacement. If the braking action is spongy or grabby, you may need to bleed it or check things for wear or corrosion. Will not likely be very expensive.
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Some times the linings are simply contaminated with oil, and must be changed
these had about 150 hours in service when the break leaked. Another A&P repaired the O'Ring but did not change the linings. brake was full hard on the pedal, but wouldn't stop the aircraft it always pulled right.

I relined the brake every thing is now working as it should
 

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Tom-D said:
Here is what you are talking about.
There really isn't a valve, as the o'ring enters the cylinder it closes the system and as it travels down the cylinder it creates pressure to extend the brake cylinder pressing the pucks to the disks.
When the pedal is released the piston / o'ring is retracted from the cylinder, then any pressurized fluid is free to return to the reservoir.
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That's a later version. Older airplanes did have a Lock-O-Seal valve affair in them. Item 17 in the picture:

Cessna brake cyl.png
 
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Dan Thomas said:
That's a later version. Older airplanes did have a Lock-O-Seal valve affair in them.
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They all worked the same way. Lock-O-Seal otherwise known as a "O" ring........ :)
Actually Dan, the cylinders I showed you are 1948 Cessna OEM from 3934V. and the IPC shows an "O"ring.
 
Dan Thomas said:
200 hours isn't much for brake linings unless you're in the habit of taxiing with the RPM at 1000 and dragging the brakes to control the speed. More likely you need some hydraulic work, like topping up the fluid in the master cylinders and maybe bleeding the air out of that left side. And I suspect that the rudder control system is out of rig, as the travels should be the same left and right. I frequently found Cessna rudder system out of rig, since mechanics often don't consult the maintenance manual and just fool with it. Proper rigging starts with the nosegear steering bungees, for instance.
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The magical whiffle tree. :)
 
When I was a freshly minted pilot and plane owner, I found a retired A&P who would help me in my hangar and sign log books. Guy is great, 45 years experience and knows all the tricks. Cost me $200 in his labor to teach, then show & tell how to IRAN the brakes.

Learned the important small stuff no one teaches you like; removing O-rings on Cleveland caliper piston to roll the it off and not pick it out with a tool and scratch the puck’s sidewall. Likewise clean light corrosion from inside the caliper with 1000 grit wet/dry paper.

He showed me how to straighten the backing plate some previous owner used as an improper jacking point. Fabricating a wood block to fit my jack and mate with the cessna main gear leg jack point.

I could write 2 pages of what I learned overhauling Cleveland brakes with a full fluid replacement for the 4.5 hours labor. It cost. For me a real bargain.
 
Tom-D said:
Do you believe Parker likes to sell parts?
Order the part number in Dan's post, then show us what you get.
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Most Lock-O-Seals have an O-ring molded right into a washer, and it's stuck there. The tiny version in that master cylinder is a small O-ring along with a washer, and you assemble it when you install it. The clearance between the seal and piston is specified at .040" and the seal can't get out of the washer.

One could measure the O-ring and look it up. It might be something like MS28775-004 and would be hard to find due to its small size. Easier just to get the right part. A mechanic can spend a lot more shop time (billed to the customer) trying to save money than if he just ordered the right thing in the first place.
 
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Tom-D said:
Actually Dan, the cylinders I showed you are 1948 Cessna OEM from 3934V. and the IPC shows an "O"ring.
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They brought that design back later on, then. I have found it in some of the last airplanes Cessna built before 1986 and in the new ones after 1996. It's simpler and works more reliably, but needs a little bit more stroke initially to get the pressure up.
 
Something to watch for in the Lock-O-Seal type cylinders: The big return pring in the bottom gets weak with age and doesn't push hard enough at the released end of the stroke to overcome the smaller spring that closes the Lock-O-Seal check valve, and pressue is trapped in the system. A hot brake caliper will expand the fluid and make the brake drag, or even lock it. Have also seen that spring put in upside-down so it's pushing on the piston instead of the adjusting nut on the end of the pushrod, and that too will cause brake drag. The small end of the spring goes against the nut.
 
What you should do is stomp on that pedal a bunch of times. The pressure can get a bit low, you just stomp on it to built the pressure back up. Happened a bunch of times on my 152.
 
NordicDave said:
Learned the important small stuff no one teaches you like; removing O-rings on Cleveland caliper piston to roll the it off and not pick it out with a tool and scratch the puck’s sidewall.
Click to expand...

That’s “O-ring 101” if you’re at all mechanically minded and work on other stuff, but yeah, stuff like that is why the typical aircraft owner needs training from a mechanic.
 
steingar said:
What you should do is stomp on that pedal a bunch of times. The pressure can get a bit low, you just stomp on it to built the pressure back up. Happened a bunch of times on my 152.
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Having to pump the brakes is a sign of a defect that needs repairing. Air in the line is most common, but a lesser-known problem is the aluminum line leading to the caliper (on airplanes that don't use a hose at the caliper). That line can get distorted when the caliper is removed to replace the linings, and it can then put outward pressure on the caliper, causing the piston to slowly collapse and leave a gap between the outer lining and the disc. That requires pumping up to close the gap.

One shouldn't tolerate stuff that doesn't work right.
 
Dan Thomas said:
Having to pump the brakes is a sign of a defect that needs repairing. Air in the line is most common, but a lesser-known problem is the aluminum line leading to the caliper (on airplanes that don't use a hose at the caliper). That line can get distorted when the caliper is removed to replace the linings, and it can then put outward pressure on the caliper, causing the piston to slowly collapse and leave a gap between the outer lining and the disc. That requires pumping up to close the gap.

One shouldn't tolerate stuff that doesn't work right.
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Advice originally came from my A&P who was also an IA. But you know better.
 
When you maintain your aircraft the way it should be, and the annual inspects and repairs stuff like leaky brakes you should have no problems the rest of the year.
 
steingar said:
Advice originally came from my A&P who was also an IA. But you know better.
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Maybe he knew you didn’t want to pay to fix it properly or he didn’t feel like it. ?

Hydraulic brakes NEVER need pumping to work correctly.

Think about how they work mechanically. Foot movement puts pressure against a column of liquid that pushes a piston against a brake pad.

This is garden tractor levels of mechanical knowledge here, not advanced hydraulic systems. :)

If you had to pump Cessna brakes, they were broken or needed bleeding and proper fluid level replaced once the air is out of the line. (Air is compressible, hydraulic fluid isn’t. Your pumping was likely displacing trapped air with hydraulic fluid until it finally was a angle column and could push the piston into the break pad when your foot moved.

Never had to pump a Cessna brake, or any brake for that matter, in my life.
 
propizza@gmail.co m said:
Dan Thomas, come to SW Florida and get out of the cold for a bit and we can work on my 172!!!
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Would be nice. Some of the coldest summer weather we've had in Canada in 30 years. The temp dropped to 9°C (48°F) last night. Unreal, for an area that can see 40°C (104°F) during a summer day.

I spent a couple of weeks in Orlando in 2008, buying a 2006 172SP and waiting for the FAA and the escrow folks to get their acts together. Should have just flown it back on the US registration and deregistered US and reregistered Cdn here.
 
Tom-D said:
Do you believe Parker likes to sell parts?
Order the part number in Dan's post, then show us what you get.
Click to expand...

https://www.airpartswest.com/800_001_6_seal_washer_800_0001_6_Cessna_Aircraft_p/800-0001-6.htm

Tom-D said:
When you maintain your aircraft the way it should be, and the annual inspects and repairs stuff like leaky brakes you should have no problems the rest of the year.
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I agree. The right part in the right place. Even a 150 deserves good brakes. McFarlane sells an entire seal kit for not much more money. I would also be looking at the rubber hoses within the system. I have seen some old and hard ones that get left way too long because they suck to get access to.
 
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