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prkaye

Well Known Member
I've had an issue with my left brake squealing loudly just as the wheel is about to stop, and also with weak brake effectiveness on that side. So this weekend I took the brakes apart on that side, cleaned the pads (including a light sanding and beveling the edges), reinstalled, re-bled and then I did the brake re-conditioning procedure (taxing at low speed with 1700RPM). Must have overdone it because when I got out and looked at the brakes, that side was SMOKING! It appeared to be the glue on the label attached to the brake caliper that was burning off. The other side wasn't as hot. Anyway, appears no harm was done, and after letting them cool down and re-testing, the brakes worked much better and were much quieter.
But wow, it was a lesson to me - brakes can get unbelievable HOT when you drag them. Makes me glad I use Ryco 782 fluid and have SS brake lines!

Question - could my light sanding of the brake pad during the cleaning have left some residue that burned off causing more of the smoking? I sanded the pads because I could feel some irregularities and rough bumps when I ran my finger over them.
 
sounds like

the piston in the caliper is sticking and its keeping the pads against the rotor. Not only can you heat crack the pad and warp the rotor, but you can, if severe enough, overheat the piston seal causing a fluid leak. Fluid leak in one side means a really hard time slowing your RV down after landing.
Tom
 
I'm with Tom... the piston in the caliper is probably sticking. If you take the caliper down for a rebuild inspect the piston closely and replace the oring with a Viton oring. Use of brakes with the "A" models can be reduced by using a little more speed when taxing and letting the rudder do the work. Also, roll out... don't try and exit the first opportunity, you can bleed off some speed and take the next exit. I've got 240 hrs on the brakes and no issues using this method. Also, make sure the brakes are not sticking at the pedals.
 
sounds like the piston in the caliper is sticking and its keeping the pads against the rotor.
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Hmmm... maybe you misunderstood, I wasn't describing a problem with the brakes sticking or the pads dragging on their own during normal use ... I was INTENTIONALLY applying brake pressure throughout a slow taxi with high RPM, keeping the pads on the rotor, to RECONDITION the pads (as described in the instructions, except I did it more aggressively than the instructions say). The instructions say that this procedure is intended to generate heat to create a glazing on the pads. The process worked - the brakes are more effective now, but the amount of heat generated, and the smoke, was surprising to me. It was also interesting to me that one side was much hotter than the other (and it was smoking).
 
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I would also look at

the pedals themselves. Lots of info on the site, but in summary, the return springs on the master cylinders are marginal. If they don't fully return to the fully open position, fluid under pressure is trapped applying continuous pressure to the brake pad.

The two fixes that worked well for me are a single long bolt at the pedal pivot point, and "helper springs" on top of the master cylinders. Ryco fluid too just in case...
 
Phil

I think that you mis-understood. The responses are intended as an explanation as to why that brake overheated. There is nothing in your procedure (sanding etc) that should have caused an overheat more than the right brake, so... it would appear that your left brake is dragging (and maybe has been for some time , thus causing the original squealing and need for attention).

Brake dragging can be caused by two things - piston hanging up (not retracting after brake application) or the master cylinder not retracting fully.

The fix for a piston hang up is to clean the piston bore and replace the seal, the fix for the brake pedal hang up is as Terry said.

Fly safe
 
Ah, ok, i see.
I actually do hear the brakes dragging a bit when I push the airplane around by hand. Hmmm. I do have springs on the master cylinders.

The fix for a piston hang up is to clean the piston bore and replace the seal
Click to expand...

Hmmm... So I have to take the caliper apart? Is this to easy to do? Are there instructions (with diagram) available? Where can the seal be purchased?
 
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prkaye said:
Hmmm... maybe you misunderstood, I wasn't describing a problem with the brakes sticking or the pads dragging on their own during normal use ... I was INTENTIONALLY applying brake pressure throughout a slow taxi with high RPM, keeping the pads on the rotor, to RECONDITION the pads (as described in the instructions, except I did it more aggressively than the instructions say). The instructions say that this procedure is intended to generate heat to create a glazing on the pads. The process worked - the brakes are more effective now, but the amount of heat generated, and the smoke, was surprising to me. It was also interesting to me that one side was much hotter than the other (and it was smoking).
Click to expand...

Hi Phil,
I never do that pad break-in procedure; I just go out and do a couple of full stop landings, usually there good after the first one. At any rate if the label on the caliper was smoking I would disassemble it and replace the O ring, it is very possibly somewhat melted and problems could occur in the near future.
 
Got my Viton orings at Grainger.
Click to expand...

Thanks!! I'll PM you my mailing address!
Could you let me know the specific part number too, in case I have to get more in the future?
Also, do you know where I can find instructions on how to disassemble the caliper to remove teh piston and replace the o-ring?
 
Phil,
Pull both calipers, replace the o-ring in each. Two reasons.

First, elastic o-rings help retract the piston (they roll just a tiny bit when the piston extends, and unroll when the pressure is released, moving the piston inward). Cleaning the piston and bore, and replacing the o-ring should eliminate brake drag, assuming the master cylinders are retracting fully.

Two, if the caliper got hot enough to darken the Cleveland label, the nitrile o-ring is toasted hard anyway. It will leak.

Lots of guys have overheated calipers while bedding pads per the Cleveland instructions. Some have set the wheelpants on fire. Nothing unusual.
 
The Cleaveland Brakes website probably has a brake down, a booklet should have came with your kit also. I will write down the part number for the Viton oring when I get them from the hangar.
 
prkaye said:
Ah, ok, i see.
I actually do hear the brakes dragging a bit when I push the airplane around by hand. Hmmm. I do have springs on the master cylinders.



Hmmm... So I have to take the caliper apart? Is this to easy to do? Are there instructions (with diagram) available? Where can the seal be purchased?
Click to expand...

It?s very simple and easy, just remove the caliper leaving it attached to the break hose/line, use the pedal to gently push the piston out, clean the boar and the piston with some scotch bright and install a new O ring. Get the O ring at your FBO or aircraft supply place, I don?t know the part #, I just took the old one in with me and they hooked me up.
 
use the pedal to gently push the piston out, clean the boar and the piston with some scotch bright and install a new O ring.
Click to expand...
Will the O-ring be visible when I push the piston out with the brake pedal? Will it then be easy to pull the old O ring out without further disassembly?

remove the caliper leaving it attached to the break hose/line
Click to expand...
The good news is that it sounds like i can replace the o-rings without having to disconnect and re-bleed my brake system yet-again. Am I interpreting this correctly?

Finally, do I need to lubricate the new o-ring before installing? If so, what do i use?
 
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Archives show...

"Standard MS replacement for the caliper o-rings is MS28775-218.
The Viton O-ring upgrade is 2-218V-75 "
 
prkaye said:
Will the O-ring be visible when I push the piston out with the brake pedal? Will it then be easy to pull the old O ring out without further disassembly?


The good news is that it sounds like i can replace the o-rings without having to disconnect and re-bleed my brake system yet-again. Am I interpreting this correctly?

Finally, do I need to lubricate the new o-ring before installing? If so, what do i use?
Click to expand...

You're going to have to dump the fluid to change the o-ring, it's the seal that keeps it in.

I'd be worried that smoke from the left brake was fluid leaking past the cooked o-ring. Unless you were taxiing in a stout right crosswind, engine torque should have worked the right brake harder.

Search the archives for mil-83282 or Royco 782 fluid. If you are using garden variety 5606, it has a low flash point.

The typical failure involves an overheated O-ring losing it's seal, spraying 5606 hydraulic fluid on a red hot brake disc and causing a fire.

Switching to 83282 and viton O-rings is trivially easy, cheap, and especially important on an A-model IMHO.
 
Ok, thanks again James.
It was actually the right brake that got really hot, not the left.
You're going to have to dump the fluid to change the o-ring, it's the seal that keeps it in.
Click to expand...
I'm having a hard time picturing this. So I use the brake pedal to push the piston out. Will then be able to simply pull the whole piston right out of cylinder? Is it attached to anything in there? I'm imagining that it must be held back in there by some spring - otherwise what pulls the piston back after the brake pedals are released?
Or do I not need to completely remove the piston to replace the o-ring? Sorry, I'm just having a hard time visualizing how this is done...
 
prkaye said:
Ok, thanks again James.
It was actually the right brake that got really hot, not the left.

I'm having a hard time picturing this. So I use the brake pedal to push the piston out. Will then be able to simply pull the whole piston right out of cylinder? Is it attached to anything in there? I'm imagining that it must be held back in there by some spring - otherwise what pulls the piston back after the brake pedals are released?
Or do I not need to completely remove the piston to replace the o-ring? Sorry, I'm just having a hard time visualizing how this is done...
Click to expand...

The piston isn't attached to anything. Imagine a metal hockey puck, with a machined groove for the o-ring.

When you take it apart, it will be obvious how it works. Brakes are stone simple.

It is possible to put the piston back inside out--make sure the o-ring is on the inside, where the fluid is, away from the brake disc. There are only two possible ways to assemble it, pick the one that gives you the most possible travel.
 
Google the brake model and you should be able to see a exploded view along with parts numbers.
 
oring

prkaye said:
Thanks!! I'll PM you my mailing address!
Could you let me know the specific part number too, in case I have to get more in the future?
Also, do you know where I can find instructions on how to disassemble the caliper to remove teh piston and replace the o-ring?
Click to expand...

If you go to Van's online catalog the parts are listed in the break-down of the brake caliper or call the customer support and they'll know which o-ring you're in need of. Very cheap until you add the shipping & handling.
Spruce also sells them!

"need them in the future": you need to order more than one and carry them in the plane in case of a brake problem when you're on a cross country, friends have had this happen so I never leave home without them!
 
Right, but the Cleveland Diagram just shows the dimensions of the O-ring, and a generic part number, not the specific Viton ring. Also, Spruce does not appear to have any Viton products in their system.

However, it's been explained to me that as long as the dimensions (width, id, od) match-up, it's good.
I guess the other factor is "durometer", whatever that means. The Viton one I found said "Durometer 75 Shore A", which I assume is ok?
 
Caliper overhaul photos

Phil,
I'm going to email you some photos of how to disassemble a caliper and change out the O-ring. I was going to send them to another builder, anyway. It's actually quite easy to do. Shore 70 would be preferable, but 75 will be OK.
Charlie
 
Email address needed

prkaye said:
Right, but the Cleveland Diagram just shows the dimensions of the O-ring, and a generic part number, not the specific Viton ring. Also, Spruce does not appear to have any Viton products in their system.

However, it's been explained to me that as long as the dimensions (width, id, od) match-up, it's good.
I guess the other factor is "durometer", whatever that means. The Viton one I found said "Durometer 75 Shore A", which I assume is ok?
Click to expand...

Phil,
Please check your private messages. I need your email address to send you photos. You won't find any Viton O-rings listed through aviation parts suppliers. Use of Viton is not "certified". Durometer relates to how hard or soft the rubber is. Higher number is harder.
Charlie
 
Orings

Phil,

I mailed you a set of Viton orings today... easy job, just clean everything up real good. :) It was nice chatting with you! If I'm in your area, we'll look you up.
 
Thanks Charlie! I sent you an email.
Darrell, thanks a million! I'll let you know how the installation goes.
Everyone else - thanks for all your tips... as usual this forum is the second best thing about being an RV builder (the first being the freedom to fly the RV).
 
Well, just one final word on this thread, I blew the right brake, also, just before OSH doing a break-in procedure as per the instructions with the new pads.

First time doing the break-in procedure in about 40 years of messing around with these things, big mistake. Someone here said he goes out and makes a hard full stop landing and that's it, which is what I usually did in the past.

The instructions said to get the temp up to 350-400, man that's hot, not that I have a brake temp gage, but it was hot - like smoking also. It got so hot it melted flat the right puck o-ring so there was a big leak but fortunately no fire.

I let the whole mess cool down and took it apart. Once you do it, it's about as simple as brushing your teeth. As luck would have it, I had the proper sized o-ring.

A while back I bought an o-ring kit from

http://oringkits.com/

The part number had 218 in it and sure enough there was a 218 in the kit, a perfect match.

That kit costs about $36 today, it is a worth while investment. I've used it to replace fuel drain o-rings also. It is a life time supply of o-rings and you'll be a hero to all the guys on the airport, everyone needs an o-ring like right now every so often.
 
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