Sticky Red Leak Left Main Gear

[BoydB]

M20J here.

Should have taken a picture, but wanted your expert opinions.  Recently started getting a leak that I notice when I arrive at my hangar.

It comes down the inside of the left main gear door, and runs onto the floor.  The quantity is not large. Spreads out to foot-diameter circle on the floor.

It accumulates into a sticky tar on the inside of the gear door.  On the floor it is visibly red but very, very sticky.

So, since it's red I was thinking brake fluid, but it does necessarily have a obvious odor, and I didn't necessarily think brake fluid would get very sticky.

Now, since it's sticky I thought, maybe evaporated fuel.  But there is no indication of a blue color at all.

Is it brake fluid, is it fuel, or is it something else? Thoughts on the common causes?

Thanks!

Boyd

[PT20J]

MIL-PRF-5606 hydraulic fluid is red and it's actually an oil. Unlike automotive brake fluid, it doesn't have much smell. It gets thick and sticky when it has been in service for a long time and should be replaced when it gets in this condition. A foot wide puddle is actually pretty large. I would check the hydraulic fluid reservoir above the battery and fill it if it is low. I would check all the hoses and fittings for leaks. It is not uncommon for the o-ring in the brake caliper piston to leak and need replacing.

Skip

[Marc_B]

Once the pads are worn enough the calipers protrude enough that the brake cylinders leak around the o-rings.  Sounds like you may be due for a brake job and flush!  That's what happened to me.  I didn't notice any change in braking, but came out to see a small amount of fluid around the wheel coming off the cylinder.

[BoydB]

Yup thanks guys. Reservoir was 4oz low. Small drop on the lowest most point there.

Mechanic got me some fluid, will watch it until annual soon.

Was thrown off by no smell and sticky fluid. Was expecting more like auto fluid. Now I know!

[Yetti]

16 hours ago, BoydB said:

Yup thanks guys. Reservoir was 4oz low. Small drop on the lowest most point there.

Mechanic got me some fluid, will watch it until annual soon.

Was thrown off by no smell and sticky fluid. Was expecting more like auto fluid. Now I know!

It's leaking, you know it's leaking.  It's not supposed to leak.   Find the leak and fix it.   The caliper probably needs new orings.  and you probably need new fluid in the system

[A64Pilot]

As it’s running down the gear leg I doubt it’s the caliper, but yes you do need to fix it before you find yourself with no brakes, which will happen. A 1 ft brake fluid leak is huge.

Red fluid is hydraulic fluid and as you don’t have hydraulic flaps, it’s the brakes

[Guest]

It’s a leaking O ring in the caliper, an AN6230-2 or MS28775-224. Item 46 in the IPC.

[A64Pilot]

10 hours ago, M20Doc said:

It’s a leaking O ring in the caliper, an AN6230-2 or MS28775-224. Item 46 in the IPC.

I’ve had leaking calipers before, everyone who’s owned an airplane very long has, but I’ve never had one leak up the gear leg?

You spend so little time in flight and of course the 100 mph wind when you lower the gear that would blow the oil off makes me think he has a leaking hose, or a loose one.

‘Should be easy to find though

[Guest]

3 hours ago, A64Pilot said:

I’ve had leaking calipers before, everyone who’s owned an airplane very long has, but I’ve never had one leak up the gear leg?

You spend so little time in flight and of course the 100 mph wind when you lower the gear that would blow the oil off makes me think he has a leaking hose, or a loose one.

‘Should be easy to find though

Where does it say or show that it's leaking up the gear leg?  In the picture above the bleeder nipple is soaked and dripping, as is the caliper between the housing and the brake plate, a sure sign the O ring at the piston is leaking.

[A64Pilot]

31 minutes ago, M20Doc said:

Where does it say or show that it's leaking up the gear leg?  In the picture above the bleeder nipple is soaked and dripping, as is the caliper between the housing and the brake plate, a sure sign the O ring at the piston is leaking.

It doesn’t I misread it it says inside of the gear door.

“It comes down the inside of the left main gear door, and runs onto the floor.”

Unless I’m mistaken the pictures were posted by someone else who did have a leaking caliper, apparently the OP posted a pic too. 

I’ve just not had a caliper leak anywhere but the caliper and usually like you say from the bleeder nipple.

But even though I misread leg when it was door, I’m not sure a leaking caliper would leak on the gear door.

But as it’s leaking really bad it ought not be hard to find the leak

[Marc_B]

Funny that this month's AOPA Pilot mag "On Course" (Feb 2023) is about the troubles with an abbreviated preflight that didn't catch a leaking O-ring in the right brake caliper that failed leading to asymmetric braking/turning into a metal pole narrowly averting collision into fuel pump taxiing over to fuel up.  ...good advice to address sooner rather than later!

[N201MKTurbo]

The problem isn’t when one brake quits working, it’s when the second one quits working…..