Break fluide leak under aircraft belly

[Ibra]

Hi all,

I guess red fluide leaking here is break fluid (MIL-PRF-5606) anyone know how the leak can be located or fixed? 

The break fluid reservoir is not empty and I never had issues with pilot & co-pilot breaks, I am not sure if it’s caused by parking break?
 

Thanks,

Edited November 12, 2023 by Ibra

[PT20J]

Master cylinders? Under left exhaust cavity behind cowl flap. 

[A64Pilot]

Find the leak first, mine was the Master cylinders, hardest part was getting them in and out, very easy to overhaul.

I only have Pilot brakes myself.

Until you discover the source, it’s all speculation, if it’s the Master cylinder, I’d overhaul, really it’s just seal replacements both of them.

I believe there is a Stat -O-Seal that’s getting hard to find. I got mine by buying an overpriced kit so another reason to do both before the source of those seals dries up.

[Ibra]

44 minutes ago, PT20J said:

Master cylinders? Under left exhaust cavity behind cowl flap. 

Thanks Skip, seems hidden there 

[Shadrach]

I’m going through this right now. I just finished resealing both master cylinders.  One has been weeping for a while.  Not as bad as what you’re dealing with, just enough to form a thin sticky line of 5606 on the outside of one cylinder.  I elected to do the parking brake as well since I was draining the system completely to make the switch from 5606 to Royco Synthetic 782.

If you’re doing it under supervision, be sure to mark or measure the location of the rod ends before disassembling the shafts.

[Ibra]

On 11/12/2023 at 10:39 PM, Shadrach said:

make the switch from 5606 to Royco Synthetic 782

Any reason why you went for this replacement?

[LANCECASPER]

33 minutes ago, Ibra said:

Any reason why you went for this replacement?

It shouldn't get dark and gooey, like the 5606.

[Shadrach]

12 minutes ago, Ibra said:

Any reason why you went for this replacement?

I’ve been told by numerous sources that it’s more resistant to “gelling”.  Early in my ownership I rebuilt both brake calipers.  I was a appalled at the condition of the existing 5606 in the lines. It wasn’t quite the color and consistency of marmalade but that was my initial comparison. It was probably 20+ years old.  
 

I now flush new 5606 through the system every 5-6 years.  I hope 782 allows me to extend the time in service to 10+ years.
 

[Jim F]

On 11/13/2023 at 6:39 AM, Shadrach said:

I’m going through this right now. I just finished resealing both master cylinders.  One has been weeping for a while.  Not as bad as what you’re dealing with, just enough to form a thin sticky line of 5606 on the outside of one cylinder.  I elected to do the parking brake as well since I was draining the system completely to make the switch from 5606 to Royco Synthetic 782.

If you’re doing it under supervision, be sure to mark or measure the location of the rod ends before disassembling the shafts.

Hi Shadrach,

Do know the procedure to clean out the lines, master cylinders, and calipers of 5606.  

Thanks Jim

[Shadrach]

15 minutes ago, Jim F said:

Hi Shadrach,

Do know the procedure to clean out the lines, master cylinders, and calipers of 5606.  

Thanks Jim

I have never cleaned or flushed the lines and I can’t speak to approved methodology or guidance. I simply pushed fresh 5606 through until there was no evidence that any of the old fluid remained. I have bled the system twice in the last 15 years and have not seen further evidence that there is any deteriorated fluid in the system. I plan on draining the system completely. Royco 782 synthetic is compatible with mineral based 5606 so I do not anticipate any issues.

[A64Pilot]

Just a flush is fine, the new fluid is completely compatible with the old, it’s also nearly fireproof, I know Mooney’s don’t really have that problem, but a brake fire gets spectacular when it lights off the magnesium wheel. I first started working on Military helicopters in 1982, and even then we used 83282, I can’t imagine why GA didn’t switch long ago. Just pump a half quart or so through each brake and it’s really well flushed.

One of the new fluids doesn’t perform as well in stupid cold and I mean stupid cold. Not sure which one because it’s never been an issue for me.

I think maybe -40F and colder?

Anyway it’s 83282 fluid your after, that’s the Mil spec number just as 5606 is.

Decent history on the subject if anyone’s interested

https://www.radcoind.com/blog-post/a-brief-history-of-u-s-military-aviation-hydraulic-fluids/

 

[A64Pilot]

Oh, I have never seen 23282 get sticky much less gooey like 5606 does, I don’t think it ever does

[Ibra]

20 minutes ago, A64Pilot said:

I can’t imagine why GA didn’t switch long ago

Only, if it saves me one billion dollar 

Thanks for the background, I guess it depends on the applications? I rarely get the breaks that hot in Mooney  I am sure RyanAir will be interested in synthetic based instead of petroleum based 

https://community.infiniteflight.com/t/ryanairs-bad-landings-explanation/269067

 

Edited November 16, 2023 by Ibra

[EricJ]

39 minutes ago, Ibra said:

Thanks for the background, I guess it depends on the applications? I rarely get the breaks that hot in Mooney  I am sure RyanAir will be interested in synthetic based instead of petroleum based 

The military and airlines switched away from  5606 decades ago.    GA is the holdout.   Airliners have used Skydrol, a synthetic hydraulic fluid, for decades, partly because it is not flammable.    It is, however, smelly, nasty stuff that if you get it on your skin you'll be miserable for a long time.

 

[Jim F]

3 hours ago, Shadrach said:

I have never cleaned or flushed the lines and I can’t speak to approved methodology or guidance. I simply pushed fresh 5606 through until there was no evidence that any of the old fluid remained. I have bled the system twice in the last 15 years and have not seen further evidence that there is any deteriorated fluid in the system. I plan on draining the system completely. Royco 782 synthetic is compatible with mineral based 5606 so I do not anticipate any issues.

Interesting, thank you

[A64Pilot]

12 hours ago, Ibra said:

Only, if it saves me one billion dollar 

Thanks for the background, I guess it depends on the applications? I rarely get the breaks that hot in Mooney  I am sure RyanAir will be interested in synthetic based instead of petroleum based 

https://community.infiniteflight.com/t/ryanairs-bad-landings-explanation/269067

Fire resistance is just one thing, we bemoan our landing gear pucks, but compared to Oleo struts they are low maintenance. I’ve seen a few Oleo’s that by the time they begin to leak they are a mess, complete disassembly and cleaning followed by every seal replaced due mostly from broken down 5606, so what does the mechanic do? Reservices it with 5606 of course pretty much guaranteeing a repeat performance in the future, but steering stabilizers often use hydraulic fluid, as well as any hydraulic system, I’d bet lunch that the cause of a significant number of the hydraulic flap Mooneys problems stem from broken down 5606, and I know it is a major cause of steering stabilizer failure. Anything hydraulic WILL have problems if serviced with 5606, because no one changes the stuff.

Army tanks have complex hydraulic systems that used to use 5606 and were subjected to flash fires from enemy fire, take a round, high pressure leak fills the tank with a fine mist of 5606 that’s then ignited. Why automatic Halon fire extinguishers were so important, fewer Tankers become “crisp critters” now with 23832

Tanks carry I’m not sure but something like 15 or 20 gls of hydraulic fluid.

But back to airplanes, I’m nearly certain that Cirrus has been plagued by brake fires, there have been several accidents, SB’s and I think even an AD addressing brake fires?

I don’t know anything about them really, but it does seem to indicate that a steerable nose wheel isn’t just an unnecessary complication doesn’t it?

Google “Cirrus brake fires” So brake fires do happen on little airplanes, just I guess not Mooney’s, seems we just flat spot tires  but I’ll take a flat spot over a brake fire.