Matco disk brake getting hot

[danny_galaga]

I figured the engine section is the best place to ask 

 

My plane has matco ph-8 disk brakes. The right one is getting much hotter than the left one. Have to add extra herbs after landing to taxi. And much harder to push back into the hangar. It looked a bit glazed, so I was hoping maybe it's suffering from a positive feedback loop whereby the more it overheats, the more glazed it becomes. The more glazed the hotter it gets. I took the caliper off, and de glazed with wet and dry and water. Also touched up the pads with wet and dry on a flat surface. The system is comically simple, and everything thing seems to moving. Pressing the brake pedal gently showed the piston moving. The caliper sliding thing slides. I'm at a loss! If I don't hear of any easier things to try by tomorrow, I'll swap left caliper for right (they are symmetrical) and see if the problem follows it.

[skippydiesel]

Speculation:

 

A brake gets hot due to friction. Friction, in this context, is when two materials/surfaces moving at diffrent speeds make contact.

Two identical (?) brake systems should deliver the same temperature IF the same forces are applied. Is this an independent brake system (as in castering tail /nose wheel) or a single acting Master Cylinder system?

Glazing is more likly to result in cooler(less effective) brakes as the smooth surface of the glazed disk results in less friction.

Difference's in materials (brake pad/disk) are likly to result in diffrent temperatures. Differences' can be caused by contamination.  Oil is a common one, but other substances eg metal filings can have a similar effect. Do you wash your brakes? If so could detergent residue be contaminating the surfaces?

Misalignment of calliper 

Incorrectly assembled or manufacturing defect, may cause the slave cylinder piston to not retract, causing the brake pad to rub/bind at all times, generating some heat that just increases with braking effort

Air in one brake line/system

😈

 

[skippydiesel]

Just another , random. thought - Are you using the correct brake fluid for your system?😈

[BrendAn]

48 minutes ago, danny_galaga said:

I figured the engine section is the best place to ask 

 

My plane has matco ph-8 disk brakes. The right one is getting much hotter than the left one. Have to add extra herbs after landing to taxi. And much harder to push back into the hangar. It looked a bit glazed, so I was hoping maybe it's suffering from a positive feedback loop whereby the more it overheats, the more glazed it becomes. The more glazed the hotter it gets. I took the caliper off, and de glazed with wet and dry and water. Also touched up the pads with wet and dry on a flat surface. The system is comically simple, and everything thing seems to moving. Pressing the brake pedal gently showed the piston moving. The caliper sliding thing slides. I'm at a loss! If I don't hear of any easier things to try by tomorrow, I'll swap left caliper for right (they are symmetrical) and see if the problem follows it.

I think you will find a tight piston.

 . Can you push the piston In by hand 

[Blueadventures]

1 hour ago, danny_galaga said:

I figured the engine section is the best place to ask 

 

My plane has matco ph-8 disk brakes. The right one is getting much hotter than the left one. Have to add extra herbs after landing to taxi. And much harder to push back into the hangar. It looked a bit glazed, so I was hoping maybe it's suffering from a positive feedback loop whereby the more it overheats, the more glazed it becomes. The more glazed the hotter it gets. I took the caliper off, and de glazed with wet and dry and water. Also touched up the pads with wet and dry on a flat surface. The system is comically simple, and everything thing seems to moving. Pressing the brake pedal gently showed the piston moving. The caliper sliding thing slides. I'm at a loss! If I don't hear of any easier things to try by tomorrow, I'll swap left caliper for right (they are symmetrical) and see if the problem follows it.

Is the piston returning (coming off, the pad retracting off the disk surface); if not that cause heat.

[kgwilson]

I agree with Brendan. I reckon the piston is not returning after braking. Pull the whole wheel cylinder apart & check for rub marks grit etc, clean everything meticulously,  reassemble & make sure moving parts i.e. the piston moves freely.

[BrendAn]

When you own Honda road bikes you learn about sticky brake pistons

[Thruster88]

My friend once had a similar problem in his Socata TB10 Tobago. Problem turned out to be the master cylinder was not able to fully retract so hydraulic pressure could not be released to the reservoir. The hotter it got the harder the brake grabbed. 

 

Do you have a park brake valve or anything that might be holding pressure. Wrong fluid and swollen orings? 

Edited 10 hours ago by Thruster88

[facthunter]

I'm with Thruster. Check residual pressure in the specific brake line.  Crack the Bleed. That master cyl may not be porting. Check there's some free play before the Piston moves. Your pads may be too thick also. Nev

[danny_galaga]

Some good thoughts there.

 

I forgot to mention that since I'm on a grass field the only time I use the brakes is PARK on start and engine run ups, and to 'unkink' the tailwheel after pulling the plane backwards out of the hangar. And then of course a quick jab when taxiing to check the brakes are working. 

 

I'm 

Edited 9 hours ago by danny_galaga

[danny_galaga]

4 hours ago, skippydiesel said:

Just another , random. thought - Are you using the correct brake fluid for your system?😈

Definitely the correct fluid. It's a mineral oil system. Just using what's recommended. My experience with hydraulic brakes in cars is that if you have air in the system, the reverse of what you are implying happens. Ask me how I know 😂