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Brake Issues

F

Frostbite023

Member
Can someone help diagnose a braking issue I am having? I am hoping this is a relatively easy fix that I can do on my own without taking another trip to the mechanic and spending $500. If you watch the video I took, you will hear the unholy screeching that my right brake is making, it also lacks the same braking power as the left brake. It still brakes, just not as well. I didn't notice any fluid on the ground during pre-flight and the brakes have been fine up to this point. Should I start with bleeding them or is there something else at play here perhaps? I haven't had a chance to check the brake pads but the brakes were checked during the pre-buy and found to be in good shape and that wasn't more than 50 hours ago. And I am not a heavy braker so I can't imagine that the brakes are worn down already (but maybe they are...).

 
My first guess is a leak in the caliper seal. It is an Oring that is easy to replace and can be done in 30 minutes if you know what you are doing. if you have flex lines on the gear leg you hold the caliper up (so air can’t flow up the brake line) when replacing the seal and bleeding isn’t necessary. To check if this is your problem look at the brake pads for wetness from brake fluid. I had the exact same problem and there was no fluid showing anywhere because the leak was so minimal.
 
seagull said:
My first guess is a leak in the caliper seal. It is an Oring that is easy to replace and can be done in 30 minutes if you know what you are doing. if you have flex lines on the gear leg you hold the caliper up (so air can’t flow up the brake line) when replacing the seal and bleeding isn’t necessary. To check if this is your problem look at the brake pads for wetness from brake fluid. I had the exact same problem and there was no fluid showing anywhere because the leak was so minimal.
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Thanks! I’ll check for that when I’m out there in a couple days and report back. So you didn’t have to also replace the brake pads? Did the contamination just wear off after a bit?

Also, you wouldn’t happen to remember the part number would you? So that I can reference the Matco brake manual and get a clearer idea of what you’re talking about.
 
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I am not convinced that the noise is brakes, there is just too little info available in that video.

I'd be suspicious of brake. pads being worn but do not know if this could lead to loss of brake effectiveness. The only way to know is to get dirty. Take off the wheel pants and learn your brakes. I think for mine that I jacked up the plane, took off the tire and then could see well. Might just be able to take some brake stuff off leaving the tire on the ground.

If the caliper seal was bad the brake fluid would leak out and you would have the pedal go to the floor without any pressure. It would be very different.

For part numbers I would start with the logs and hopefully all of the other written stuff that came with the plane. If not, start your own chart for such as you learn the plane, help the next time and next guy.
 
I would also guess that this noise is the result of some contamination on the brake disc. What you describe as a lack of pressure on the right pedal supports that theory. As mentioned, this starts with removing the wheel pant and taking a closer look at the disc for clues.

Do you notice this only when applying the right brake? Is there any noise from the brakes when rolling the airplane around manually and no brakes applied?
 
Frostbite023 said:
Thanks! I’ll check for that when I’m out there in a couple days and report back. So you didn’t have to also replace the brake pads? Did the contamination just wear off after a bit?

Also, you wouldn’t happen to remember the part number would you? So that I can reference the Matco brake manual and get a clearer idea of what you’re talking about.
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Done properly you need to replace the pads on that side, that is Matco’s recommendation. When it happened to me I thoroughly cleaned the whole rotor and pads with spray brake cleaner. Then reassembled. The brakes worked good and the noise went away for about 2 days then came back. Since I hadn’t fixed the real problem, “the leak” the rotors and pads were wet again.
 
It sounds like it might be a touch of what I would characterize as "brake pad/disk resonance" -- a resonant vibration resulting in an audible sound?? IMHO it could be a slightly contaminated brake pad/disk interface possibly caused by a nearby slight fluid leak or perhaps a newly installed pad and/or brake disk that has not yet fully seated itself or has a bit of a glaze. As mentioned above, you should inspect the brake area and see if there are any noticeable leaks or fluid staining. As RNB noted, it's time for you to get down and dirty and learn about your airplane. Enjoy the grime!!
 
Had a similar noise with my brakes and the right brakes did not have the same braking power as left. It turned out to be a brake fluid leak right where the aluminium tubing attaches to the brakes. After fixing it, bleeding and cleaning the pads with alcohol the noise was still there. It eventually went away as I used the brakes. So check if you see air bubbles in your brake lines and for any fluid after removing wheel pants.
 
Same here – I noticed that I'd get some chattering from the left brake over the course of a few months, then during a preflight I found a leak from the landing gear bracket that the lines connect to.

Took the opportunity to replace the stock lines with ones from TS Flightlines. I had never bled the brakes in the 4 years of ownership, so when I jumped in after doing the whole repair, the difference in braking feel was night & day.
 
N8DAV8R said:
I would also guess that this noise is the result of some contamination on the brake disc. What you describe as a lack of pressure on the right pedal supports that theory. As mentioned, this starts with removing the wheel pant and taking a closer look at the disc for clues.

Do you notice this only when applying the right brake? Is there any noise from the brakes when rolling the airplane around manually and no brakes applied?
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Only when applying the right brake. No noise when rolling and not applying brakes.

Quick update as well...removed the wheel pant and snapped some pictures and sent to local light sport mechanic. I have replaced brake pads on cars before but for some reason I feel a bit apprehensive about doing on my plane. Decided that I'm going to take it to him and watch him do it and hopefully find the leak (if there is one). While I'm at it, I'm going to replace both sets of brake pads, replace the brake fluid with Royco 782, and also replace the o-ring per SL-00047. He suggested possibly replacing the brake rotor if it's damaged but I've only got about 350 hours on the aircraft so I'm hoping that's not necessary, especially since they are $133 each and I'm already feeling the drain. I bought the rapco tool for the brake pads to hopefully speed things up as well.

Any special way to know if I've got the brake lines from TS Flightlines? I was thinking that would be a worthwhile upgrade as well but I'm not sure if I already have them.
 

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Frostbite023 said:
Only when applying the right brake. No noise when rolling and not applying brakes.

Quick update as well...removed the wheel pant and snapped some pictures and sent to local light sport mechanic. I have replaced brake pads on cars before but for some reason I feel a bit apprehensive about doing on my plane. Decided that I'm going to take it to him and watch him do it and hopefully find the leak (if there is one). While I'm at it, I'm going to replace both sets of brake pads, replace the brake fluid with Royco 782, and also replace the o-ring per SL-00047. He suggested possibly replacing the brake rotor if it's damaged but I've only got about 350 hours on the aircraft so I'm hoping that's not necessary, especially since they are $133 each and I'm already feeling the drain. I bought the rapco tool for the brake pads to hopefully speed things up as well.

Any special way to know if I've got the brake lines from TS Flightlines? I was thinking that would be a worthwhile upgrade as well but I'm not sure if I already have them.
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Sean---look at the brake rotor in pic 2. Center shows distinct discoloration vs the other parts. Also--possible rivet drag marks on the rotor. Pull everything off and inspect.
 
Fear not -- much easier than auto brakes. Those pads look like they're due for replacement, and the rotor looks questionable in the photo but deserves a better look. The Rapco tool is what you want.
 
I ended up purchasing a new rotor from Matco, there wasnt any option for expedited shipping so I'm unsure if it's going to get here before I head to the shop next week. Couple questions, is there any reason I shouldn't just get the rotor resurfaced and keep the one i bought as a backup. And if I do just replace the pads and run them on the old rotor until the new one comes in, any dangers there?

One other note, I was going through the maintenance logs from the old owner and found an entry where he was also having brake chatter. Log says the mechanic replaced the pads and sanded the rotor with 1000 grit sandpaper. This was approximately 100 hours ago.
 
I have turned my own when needed. New rotors are .180 thick. My current ones with 1750 hrs are .140, they will be replaced with new ones on the next brake job. The thinner the rotor the less heat they can dissipate. When I turn them it is a very light cut .003 - .005.
 
Frostbite023 said:
Only when applying the right brake. No noise when rolling and not applying brakes.

Quick update as well...removed the wheel pant and snapped some pictures and sent to local light sport mechanic. I have replaced brake pads on cars before but for some reason I feel a bit apprehensive about doing on my plane. Decided that I'm going to take it to him and watch him do it and hopefully find the leak (if there is one). While I'm at it, I'm going to replace both sets of brake pads, replace the brake fluid with Royco 782, and also replace the o-ring per SL-00047. He suggested possibly replacing the brake rotor if it's damaged but I've only got about 350 hours on the aircraft so I'm hoping that's not necessary, especially since they are $133 each and I'm already feeling the drain. I bought the rapco tool for the brake pads to hopefully speed things up as well.

Any special way to know if I've got the brake lines from TS Flightlines? I was thinking that would be a worthwhile upgrade as well but I'm not sure if I already have them.
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You do not have TS Flightlines brake hoses .... you have the original design aluminum tubing - note the "curly cue" around the gear leg so the brake line can flex as the gear leg does (particularly on t/o & landing). TSF Hoses go directly from inside the fuselage, along the gear leg to the caliper (since they can easily flex).
 
So a little bit of good news, bad news. I had a mechanic come out and help me replace the brake pads. After watching him do one side I felt confident and performed the change on the other side. So glad I bought that brake rivet tool, made it a breeze. After replacing the pads and bleeding the brakes the horrible sound is gone and brake power is restored. Rotors appear to be okay still, but I still have one on order just in case for the future. However, upon inspecting the lines he discovered what appears to be a leak under the pilot side dash. The picture shows the coupler. I never noticed any fluid on the floor but the pre-buy did note that there was literally a single drop of fluid that had collected on one of the lines. But since there wasn't any on the floor I just figured it was pretty much a non-issue, obviously that was the wrong decision. After we bled the brakes I am now noticing brake fluid on the floor (small amounts, picture attached) after a flight. So I definitely need to replace the connection fitting, but I am not seeing it in section 28iS/U of the brake system diagram. Anyone know the part number and whether I can just get a replacement at a hardware store instead of ordering through Vans?
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Seems like the kind of part that is readily available, just need to know the hose size.

I do not know standards but perhaps the line comes out under too much tension due to the angle?

I see a lot of people wanting fancy braided hoses but like the clearer look of stock. It allowed me to see air bubbles when bleeding.
 
Odd place for a leak because no pressure on that fitting. Fluid is at 1 atmosphere - same as brake reservoir. I would try re-seating the hose connection...
 
I had the same thing. Not usually the fitting to the lines, but the fitting to the reservoir. Should not have to re-bleed if the lines are keep up.
 
Frostbite023 said:
… upon inspecting the lines he discovered what appears to be a leak under the pilot side dash. The picture shows the coupler. I never noticed any fluid on the floor but the pre-buy did note that there was literally a single drop of fluid that had collected on one of the lines. But since there wasn't any on the floor I just figured it was pretty much a non-issue, obviously that was the wrong decision. After we bled the brakes I am now noticing brake fluid on the floor (small amounts, picture attached) after a flight. So I definitely need to replace the connection…
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That’s interesting issue. It’s a discontinued Parker “Pneumatic Push-In Fitting” intended for compressed air, with this note from Parker; “Other Fluids: Please Consult Us” Van’s has used this fitting satisfactorily for over ten years so I’m pretty sure Vans confirmed the fitting is compatible with MIL-PRF-83282 and MIL-H-5606A hydraulic fluid…ONLY.

Your leak doesn’t appear to be at the 1/8 NPT brake reservoir connection, it appears to be plastic degradation. This in combination to your initial issue of brake fluid on the pads may indicate hydraulic fluid contamination, or the use of improper hydraulic fluid that has compromised the brake system. Aviation brake systems are incompatible with automotive brake fluid.
 
MMiller said:
That’s interesting issue. It’s a discontinued Parker “Pneumatic Push-In Fitting” intended for compressed air, with this note from Parker; “Other Fluids: Please Consult Us” Van’s has used this fitting satisfactorily for over ten years so I’m pretty sure Vans confirmed the fitting is compatible with MIL-PRF-83282 and MIL-H-5606A hydraulic fluid…ONLY.

Your leak doesn’t appear to be at the 1/8 NPT brake reservoir connection, it appears to be plastic degradation. This in combination to your initial issue of brake fluid on the pads may indicate hydraulic fluid contamination, or the use of improper hydraulic fluid that has compromised the brake system. Aviation brake systems are incompatible with automotive brake fluid.
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We didn't find any evidence of brake fluid leaking at the calipers during the brake pad change, and I don't see any maintenance logs that talk about adding fluid. I can't be certain what was put into the system the first time but it was built by GA Aerospace so I want to believe that they knew the correct type of fluid to add. I also can't be certain brake fluid wasn't added and not logged. I'm hoping that it's just a failing connection.
 
Frostbite023 said:
, is there any reason I shouldn't just get the rotor resurfaced and keep the one i bought as a backup. And if I do just replace the pads and run them on the old rotor until the new one comes in, any dangers there?
Click to expand...
A poster above said he turns his disks down to .140" Need to exercise caution here. Like all brake rotors, yours have a minimum thickness specification. You need to find that spec for your rotors and replace them if below/thinner. A good portion of the heat from braking goes into the rotor and they must be thick enough to handle that without deforming, hence the min thickness.
 
Frostbite023 said:
So a little bit of good news, bad news. I had a mechanic come out and help me replace the brake pads. After watching him do one side I felt confident and performed the change on the other side. So glad I bought that brake rivet tool, made it a breeze. After replacing the pads and bleeding the brakes the horrible sound is gone and brake power is restored. Rotors appear to be okay still, but I still have one on order just in case for the future. However, upon inspecting the lines he discovered what appears to be a leak under the pilot side dash. The picture shows the coupler. I never noticed any fluid on the floor but the pre-buy did note that there was literally a single drop of fluid that had collected on one of the lines. But since there wasn't any on the floor I just figured it was pretty much a non-issue, obviously that was the wrong decision. After we bled the brakes I am now noticing brake fluid on the floor (small amounts, picture attached) after a flight. So I definitely need to replace the connection fitting, but I am not seeing it in section 28iS/U of the brake system diagram. Anyone know the part number and whether I can just get a replacement at a hardware store instead of ordering through Vans?
View attachment 100900
View attachment 100902
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I have a very similar issue on my RV-12.

At ~160 hours on the airframe I found a drop of red liquid on the vinyl of the floor mat. One of the brake lines above had a drop of brake fluid hanging from it.

In an attempt to figure out where it was leaking from I placed some white paper towel pieces in key locations. It’s clear that isn’t leaking where the brake lines connect to the fitting. I believe that it is weeping where the fitting screws into the brake reservoir. But, I can’t rule out that the fitting itself is weeping.

I ordered a replacement fitting from Amazon. Much lower shipping cost.

The picture shows how much brake fluid has been collected in ~10 hours. I haven’t replaced the fitting yet.

Brett H
Columbus IN N4BHIMG_3723.jpegIMG_3721.jpeg
 
Brett H said:
But, I can’t rule out that the fitting itself is weeping.
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Hi Brett.I just had breakfast Saturday morning at KBAK but I didn't see any activity at your hangar or I would've stopped by.

At about 160 hours my 12iS had that drop of brake fluid on the vinyl, as well. Turned out to be the reservoir leaking. The fluid followed the lines to the fitting which stopped the flow and allowed fluid to gather until it dripped.
 
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Brett H said:
I have a very similar issue on my RV-12.

At ~160 hours on the airframe I found a drop of red liquid on the vinyl of the floor mat. One of the brake lines above had a drop of brake fluid hanging from it.

In an attempt to figure out where it was leaking from I placed some white paper towel pieces in key locations. It’s clear that isn’t leaking where the brake lines connect to the fitting. I believe that it is weeping where the fitting screws into the brake reservoir. But, I can’t rule out that the fitting itself is weeping.

I ordered a replacement fitting from Amazon. Much lower shipping cost.

The picture shows how much brake fluid has been collected in ~10 hours. I haven’t replaced the fitting yet.

Brett H
Columbus IN N4BHView attachment 101035View attachment 101036
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I'll be replacing mine within the week hopefully, I'll report back if that solves the issue. Is this a known issue and something that needs to be replaced semi-regularly?
 
Frostbite023 said:
Is this a known issue and something that needs to be replaced semi-regularly?
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Approaching 500 hours on the 12iS and this has occurred only once. Never heard anyone else speak of it until now but then I never discussed it either before this forum conversation.
 
Amadeus said:
Hi Brett.I just had breakfast Saturday morning at KBAK but I didn't see any activity at your hangar or I would've stopped by.

At about 160 hours my 12iS had that drop of brake fluid on the vinyl, as well. Turned out to be the reservoir leaking. The fluid followed the lines to the fitting which stopped the flow and allowed fluid to gather until it dripped.
Click to expand...

Sorry that I missed you at KBAK. Next time please let me know when you will be at KBAK.

It’s interesting that you had the same leak after the same number of hours. I’m surprised that after initially not leaking that a leak developed after 160 hours.

Brett H
Columbus IN N4BH
 
Frostbite023 said:
I'll be replacing mine within the week hopefully, I'll report back if that solves the issue. Is this a known issue and something that needs to be replaced semi-regularly?
Click to expand...
For reference, I attached two pictures that show how the leak looked when I first found it.

My understanding is that that the brake reservoir and fitting that screws into it are used in most of the RV models. So, would be surprised if it is a known issue.

Unfortunately the fitting has pipe threads and needs to be installed to a particular orientation. So, when I replace mine, I am going to remove the pre-applied sealant on the replacement fitting and use Loctite 567 thread sealant. Just what I am planning on doing.

Brett H
Columbus, IN N4BH

IMG_3543.jpegIMG_3542.jpeg
 
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The Matco brake people recommend Loctite 567 for the NPT sealing. It has worked for me in similar fixes.

Screen Shot 2025-11-04 at 8.07.23 AM.png
 
Well....replaced the shark bite fitting last night and used the recommended loctite and unfortunately the issue persists. My next course of action is going to be replacing the line. I suspect that maybe the one brake line is perhaps a touch too short and the bend required to get it into the fitting is creating too much pull. As a side note, it only leaks when actively braking. I clean up the fluid and there's no new leaks when returning to the plane even days later.
 
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