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Mobil 1 ATF as brake fluid..

Tram

Well Known Member
I've been using Royco 782 but I am considering moving to M1 ATF, just due to the ease of aquiring from the local Autozone vs ordering it in.

Has anyone gone to M1 ATF without changing all the seals in the entire system without issue?
 
Started out life with it in 2010. Been using it since with no issues. Stock system with the exception of braided teflon lines.
 
Started out life with it in 2010. Been using it since with no issues. Stock system with the exception of braided teflon lines.

Did some reading and found others feel the same way. I'll drain the old and put in the new.
 
I've been using Royco 782 but I am considering moving to M1 ATF, just due to the ease of aquiring from the local Autozone vs ordering it in.

Has anyone gone to M1 ATF without changing all the seals in the entire system without issue?

Tram .... I too wanted a brake fluid that can be easily located in time of dire need. I decided on using Amsoil ATF fluid because it has a higher flash point (453* F) than the Mobile 1 (which is 428*F) .... during a trip if a top-off is necessary, Moble 1 ATF can be sourced at any auto parts store and will mix well with the Amsoil. Been using the ATF fluid in the brake system for 9 months without any issues .... brakes are nice and solid.

Happy flying,
 
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Tram .... I too wanted a brake fluid that can be easily located in time of dire need. I decided on using Amsoil ATF fluid because it has a slightly higher flash point than the Mobile 1 (over 450* if memory serves me).... during a trip if a top-off is necessary, Moble 1 ATF can be sourced at any auto parts store and will mix well with the Amsoil. Been using the ATF fluid in the brake system for 9 months without any issues .... brakes are nice and solid.

Happy flying,

I don't understand this fascination with auto parts store supplies, my guess is one could find standard 5606 at practically every airport in the world, ATF well not so much.
 
I don't understand this fascination with auto parts store supplies, my guess is one could find standard 5606 at practically every airport in the world, ATF well not so much.

What you say is true Walt and certainly holds a lot of weight coming from you.

The issue some of us want to avoid, if possible, is being stranded some late afternoon at a smaller airport that looks like a ghost town (which many do these days). Even at larger fields 5606 has to be ordered at times if the FBO is out of stock ... as a friend of mine recently experienced.
 
I don't understand this fascination with auto parts store supplies, my guess is one could find standard 5606 at practically every airport in the world, ATF well not so much.

If the local airport has it, great. Many, actually, do not - or if they do (like my home base) you need to get it sometime between 8:00am and 5:00pm, M-F and many of us are at work during those times.

ATF-1 has a significantly higher flashpoint as well (220ºC vs. 104ºC) without real downsides compared to 5606. My question to you would be what does using 5606 bring to the table for our use that ATF doesn't? When I was faced with this decision, I couldn't find anything to recommend it, other than "it's what certified aircraft use". Have I been missing something for the last several years and 700 flight hours?
 
4+ years, stock system with steel braided lines in the cockpit (and for the coil around the axle at the bottom), Mobil 1 ATF the whole time, no issues.

Only issues I ever had were very early on, getting rid of system leaks because of the *&%$# NPT fittings. Finally went to Teflon paste, and haven't had any problems at all since.
 
I switched over to it the last time I was in my brakes (previous owner put pistons in backwards). All the original fluid on one side had leaked out anyway, and I like the higher flash point of the ATF.
Straight swap where I just drained it completely, ran ATF through for a bit as a flush, then filled it up with ATF.
So far 0 problems, works just as good as the old stuff.
 
I don't understand this fascination with auto parts store supplies, my guess is one could find standard 5606 at practically every airport in the world, ATF well not so much.

We are both thinking alike.

I have been using MIL-PRF-83282 for years. It is the synthetic replacement for 5606 and is compatible with 5606. Either can be used with the other. 5606 is all we need but the higher price synthetic MIL-PRF-83282 replacement has a higher flash point.

Would love to see those using ATF run some tests.
1. Can ATF and 5606 or Mil-PRF-83282 be mixed together?
2. How well do O-Ring seals & Viton seals hold up long term with ATF?
3. What changes to the properties of seals with long term exposure to ATF?

Inquiring minds want to know.
 
What you say is true Walt and certainly holds a lot of weight coming from you.

The issue some of us want to avoid, if possible, is being stranded some late afternoon at a smaller airport that looks like a ghost town (which many do these days). Even at larger fields 5606 has to be ordered at times if the FBO is out of stock ... as a friend of mine recently experienced.

Hate to say it but the best way to avoid the above scenereo is to take care of your equipment (regular inspections and action taken when discrepancies are found). God forbid you spend the time every few months to actually pull the wheel pants, check the pads, check for leaks, air up the tires etc..

Rarely does the brake system just fail and puke all its fluid. I just had an airplane in here where the owner admitted the right brake had been leaking for a few months but elected to just keep adding fluid until he brought it in.

After we discussed the possible outcome of a failed brake, and how lucky he was, I doubt he will let this go again in the future.

PS: I use the 83282 (Royco 782) exclusively, I won't personally service an airplane with ATF.
 
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During any kind of a brake leak or failure repair, brake fluid is the LAST part you need.......:D
 
They all mix together fine.

We are both thinking alike.

snip

Would love to see those using ATF run some tests.
1. Can ATF and 5606 or Mil-PRF-83282 be mixed together?
2. How well do O-Ring seals & Viton seals hold up long term with ATF?
3. What changes to the properties of seals with long term exposure to ATF?

Inquiring minds want to know.

I've been using the stuff for years (since 1990?) in many different types of aviation applications. It is also available in any city you might find yourself stranded in - even at any auto fuel station that might be nearby. Mixing the different fluids poses no operational problems - they are all 'mineral' type fluids.

Also - you do know that Home Depot (and most hardware stores) carries emergency use O-rings for your brake calipers? Just in case! Grab the ruined ones and get a set to match.

I can't see any difference in O-ring life, using any std material O-rings. Elec over Hyd pumps (boat trim systems, EXP aircraft R/G systems, etc) also use ATF with no issues.

Auto brake systems use a different seal material, so mineral fluids cannot be used there..

Carry on!
Mark
 
Outside of "I won't use it.." would you be willing to explain why you see it as an issue?

You bet, because it's not an approved fluid by any of the brake or airframe manufactures that I'm aware of (please correct me if I'm wrong).
And I freely admit to not being as smart as the manufactureres of these systems so I tend to go with their recommendations.

I'm not one to be overly concerned about lawsuits and such, but if it ever came up it would be awfully hard to explain why you elected to use transmission fluid in a brake system rather than the recommended fluid or an approved substitute.
 
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Fair enough. I can't say that I'd use it in a customers aircraft if I were an A&P, actually but m fairly certain there'd be zero chance of me using anything but what the manufacturer called for, especially in our sue happy society.

Just called my local airport, anything I need is going to have to be ordered. Zero brake fluid, and we are a fairly "large" non-towered field.
 
Flame Suit On ?

I like the higher flash point protection. Along with the Mobil 1 ATF, I use viton o rings in the calipers for increased temperature protection. Neither one should be required, HOWEVER there have been a few Cirrus SR 22 wheel fire incidents where and extended long taxi in very strong X winds required extended brake application that compromised the buna N orings with a wheel pant fire resulting when the 5606 leaked onto the hot disks.

Do your own research carefully but as an experimental you can decide accordingly.

YMMV
 
You bet, because it's not an approved fluid by any of the brake or airframe manufactures that I'm aware of (please correct me if I'm wrong).
And I freely admit to not being as smart as the manufactureres of these systems so I tend to go with their recommendations.

I'm not one to be overly concerned about lawsuits and such, but if it ever came up it would be awfully hard to explain why you elected to use transmission fluid in a brake system rather than the recommended fluid or an approved substitute.

I believe BMW recommends ATF in some of their power steering systems...

I wouldn't put so much stock in "approved fluid" lists from manufacturers as to *never* stray from them, albeit normally I'll abide by their recommendations for reasons as stated above.

But really...for brakes, as long as the fluid is compatible with the seals, what else is there? Aluminum lines, flared tube fittings, and such?
 
I like the higher flash point protection. Along with the Mobil 1 ATF, I use viton o rings in the calipers for increased temperature protection. Neither one should be required, HOWEVER there have been a few Cirrus SR 22 wheel fire incidents where and extended long taxi in very strong X winds required extended brake application that compromised the buna N orings with a wheel pant fire resulting when the 5606 leaked onto the hot disks.

Do your own research carefully but as an experimental you can decide accordingly.

YMMV

Just an FYI, Flash point of Royco 782 and Mobil 1 ATF appear to be about the same 445F/220C.

http://www.qclubricants.com/royco/royco_782.htm
 
ATF fluid is used in HIGH pressures in auto trans for years, much harder application,an heat temps as well.I would have used in my RV, but AP is old school and would not let me
 
Just a point of reference...in typically vague terms, the technician's manual for Parker (Cleveland) brakes says:

Hydraulic Applications - Use fluids compatible with the system
MIL-H-5606 / MIL-H-83282 (Red Oils)
Skydrol ? Only compatible with itself

So there's probably some "wiggle room" if you read it correctly, in that "fluids compatible with the system" could include something like Mobil 1 Synthetic ATF (provided one does the research to determine that it is, in fact, compatible with the system). Since the system is basically aluminum parts and some sort of o-rings...seems like as long as it's compatible with the type of o-rings installed, you're good to go. No?
 
Slightly OT...but related (wheels and brakes and their lubricants and such)...

A buddy of mine had a sure-fire way to deal with his SO when he was working on anything mechanical and he was getting too much "help"...

SO (for the umpteenth time): Are you sure there's nothing I can help with?
Him: Oh, yeah, sure...give me a handful of grease, wouldja?

Always worked to clear the shop so he could proceed in peace. :)
 
Hmmm.

I have Grove calipers and master cylinders. At first condition,I found one leaking caliper, which has been a problem for me. This would be the third time I've rebuilt the calipers. But this isn't about the calipers. I took the opportunity to switch from 5606 to M1 ATF when I rebuit the calipers. A month later....Today, after taxiing in, I smelled and found leaking fluid. LH master was leaking at the rod seal - or that's what I'm assuming. I doubt the static seal gave it up.

Groves were early 2008 manufacture, saw 5606 fluid in 2012, didn't taxi or fly until 2016. Just a data point, really. Five bucks and three hours of painful labor, this too shall pass. Is the fluid change root cause? Dunno, just something to consider.

The upside? 1.2 hours on he Hobbs this morning. ;)
 
Good idea, but

Good idea, but not doing that for two reasons. The first is past experience with Mobil change overs resulting in near term leaks. Engines, transmissions, diffs, clutch master and servos. It happens sometimes. It's possible the shaft is scratched too, I'll know when I get it to the bench. Second is the response I got from Grove (not Rob) back in 2014 during my second rebuild, which was sympathetic, but not helpful beyond basic diagnostics/inspection. It's ok at the moment. If it happens again, I may take your suggestion. I just hope to not get any of the (STINKY) M1 in the carpet. ;)
 
Check with the component manufacturer to see that fluids are compatible with their seals. May be a point where its fine for a while, but then begins to affect the sealing properties of the O'Rings.
Dont go against the manufacturers recommendation because getting the fluid is easier. If in fact there was a catastrophic failure, and you were using an unapproved fluid, the legal outcome might be disasterous.

Tom
 
No more leaks

Brake calipers that sit for several years have the o rings set up with a flat spot.
At least the o rings are not as live as they would be if they were new and just installed.

I once purchased an aircraft that had sat for a few years. On a concrete floor it could sit for a week with no leaks. Then I would fly it 1 hour, land and have no brakes. Check the reservoirs and they were empty. So I would re fill them, bleed the brakes nice and solid. Then I would sit and hold my feet on the brakes for 10 minutes. Get out and check ... no leaks and a nice clean floor.

A week later still no leaks so I would fly it for an hour or so and land with no brakes and empty reservoirs again. The slip stream made negative pressure by the calipers in flight, and that would drain the brake fluid before landing.

So I put in new buna N o rings and that solved it. The old O rings had flat OD's and look more like D rings than O rings.

In a different AC I did use Viton O rings with Mobil one and have had zero issues for 7 years now. If I had known about the Royco fluid (that Walt referred to) has the same higher flash point as the Mobil 1 ATF, I would have used the Royco.
 
I'd do Mobil 1 again without hesitation

Walt's a good friend of mine and he has some excellent points about using "unapproved fluids".

I'm an A&P but I don't have near the aircraft experience Walt has.
I only worked as an A&P for a few years back in the 70's :)

Data points:

I put Mobil 1 in my brakes back in 2008 due to the good reviews right here on VAF. First flight was October that year.

1450 hours and 9 years with ZERO issues. Never even had to add any fluid.
Now I'm wondering if I should flush some new fluid through the system?:)

Another silly reason I didn't go with 5606 was I never liked working with it.
The smell and the way it gets sticky when it "dries".

And as far as our experimental planes go I thought you could use coconut oil in your brakes if you wanted to. I just checked, coconut oil doesn't even start to smoke until 350 degrees! LOL.

Mark
 
Just another old wives tale that ATF is lacking something,and as a result certified keep using special fluid.It is slight possibility that very old car ot airplane it might not be compa6ible !
 
ATF isnt lacking anything. It actually has "other things" in it, like friction modifiers to help with the clutch packs in the tranny. Those dont make much difference a brake system; verifying seal compatibility is all thats required.

In a sense general, any "hydraulic" fluid would work because its the liquid incompressibility characteristic that were after here. Additional characteristics that make it compatable with flight regimes, water absorption etc etc are what would make it (or any fluid) approved for airplanes. My guess is that were just not operating in the extreme environments that approved fluids are tested to so we can get away with Mobil1 in this application. IOW, "its no factor". I plan on using it. Each to his own however.
 
I've personally never had a brake system go dry while flying but they do sometimes get a low if not checked every so often and serviced every so often but the thought comes to mind that if you could service your brakes at a field where there's no one around you must be carrying tools, as most of us do, and if so why not store a small bottle of 5606 in your tool bag? Those little plastic bottled water bottles work great for fluid, cleaners, etc. small and easy to carry in your tool bag. Unless you've blown out a brake system very little fluid is needed to fill a low brake.
 
Mobil 1 ATF

I converted to Mobil 1 ATF 4 years ago and have had good service and no problems. At the time of the conversion I also changed out the caliper o rings to Viton. Both changes were to raise the "flash point" and to use a product that I can purchase most anywhere.

To each his own.

Cheers,

db
 
I am just curious. My -7 is not flying yet. Do you have to add fluid out on a trip very often? In 5000 hrs of flying a pretty good assortment of homebuilts and certified planes I cannot ever remember needing to add brake fluid when I was on the road.
 
I am just curious. My -7 is not flying yet. Do you have to add fluid out on a trip very often? In 5000 hrs of flying a pretty good assortment of homebuilts and certified planes I cannot ever remember needing to add brake fluid when I was on the road.

500 hours w/ M1 ATF and no issues (after I fixed leaks due to *&^% NPT fittings, but that was a different issue). I haven't even had to add any fluid yet (knock on wood).

It's not adding or topping off while away from home that I would worry about...it's a leak that requires disassembly/repair in the field, which then means possibly draining and filling/bleeding a brake line. That's why I chose ATF...I can get it pretty much anywhere, and don't need to carry any around with me.
 
In a perfect brake system (no leaks) if your reservoir was low on fluid, it would mean that your brake pads are worn down and have moved toward the disc along with the piston. If you push the piston back in and installed new pads, the fluid should be full in the reservoir.

Leaks are the only reason to add fluid between brake pad service. This is not to say you shouldn't replace the brake fluid at pad change..... Just pump it through as you add fresh fluid to the reservoir.
 
I've been using Mobil ATF in my brakes for the last 5 years and 900+ hours. No problems. It has a higher flash point than 5606 - I had a much harder time inducing ATF to combustion than 5606 when I proved this for myself. It is compatible with the standard seals etc no only by specification but also by empirical evidence. In the world of experimental aviation, this is perhaps one of the "safest" experiments I have performed.

To claim that it is not safe because it is not "certified" is cowardice, done perhaps only to prop up ones own choice or to try to promote some kind of air of superior knowledge where none otherwise exists. Certified does not mean superior; if it did, we'd all be flying factory built aircraft which come complete with certified brake fluid.

Walt and others engaging in the FUD around lawsuits and such seem to be doing so out of ignorance - does it really pass the smell test that a lawsuit would zone in on the brake fluid while at the same time ignoring the amateur built status and use of uncertified parts *provided by the kit manufacturer*?
 
David that is a great point. My thought was that IF there was compatibility issue they would say so. Beringer has 2 different versions of their stuff---one for DOT4 and one for mineral oil meeting Mil-PRF-87257. So I would think that unless the ATF met the 87257 specs dont use it in Beringer systems. Grove, Matco, Cleveland, dont know.

Tom
 
Of all the things to argue about on this forum, this has to be one of the more pedantic.

Two relevant/amusing experiences from my past.

When I was in the AF stationed in England, my Jaguar had a bad front seal leak. Being a poor airman at the time, I did not have the resources to keep throwing ATF into it every day nor the motivation to spend the weekend dropping the tranny and replacing the seal. What I did have though, was access to an unlimited supply of 5606. So that's what I filled it with. Every day for months. I'll bet I ran 50 gallons of the stuff through that tranny before I finally installed a new seal. Was still running fine on 5606 when I transferred back home a year later.

When I picked up my Tri Pacer and serviced the brakes, I found that the previous owner had serviced it completely with DOT 3 (automotive) brake fluid. The Certified Cleveland brakes didn't seem to mind one bit. (Yes, I went with 5606)


I have a lifetime of 5606 around, but I'd have no trouble at all adding ATF out on the road if required. Power steering systems use it as do convertible top systems.

Is it just a slow week on the forum?
 
To claim that it is not safe because it is not "certified" is cowardice, done perhaps only to prop up ones own choice or to try to promote some kind of air of superior knowledge where none otherwise exists. Certified does not mean superior; if it did, we'd all be flying factory built aircraft which come complete with certified brake fluid.

Walt and others engaging in the FUD around lawsuits and such seem to be doing so out of ignorance - does it really pass the smell test that a lawsuit would zone in on the brake fluid while at the same time ignoring the amateur built status and use of uncertified parts *provided by the kit manufacturer*?

Hmm, never been called a coward before for sharing my opinion. Personally I don't really care what you think or prefer to use in your own system, but recommending it to others just because you think it ok is just plain wrong IMO.

Neither Van's nor any brake manufacturer I'm aware of has tested or approves using ATF in their brake systems, but I guess you're just smarter than they are.

Until they do, thank you very much but I'll stick with the "approved" fluids.
 
Brake Fluid.

When I picked up my Tri Pacer and serviced the brakes, I found that the previous owner had serviced it completely with DOT 3 (automotive) brake fluid. The Certified Cleveland brakes didn't seem to mind one bit. (Yes, I went with 5606)


For what its worth: It was years ago, but I once spent days replacing parts and rebuilding the brake system on a Cherokee 6 that had been operated for a couple months with automotive (Dot 3) brake fluid. Many of the ?O? rings were very soft and gummy. On my 9 I will use the higher flash point Aviation Grade Fluid or ATF. Only 5606 in the Pacer.


Don Broussard
RV9 Rebuild in Progress
57 Pacer
 
I've been using Mobil ATF in my brakes for the last 5 years and 900+ hours. No problems. It has a higher flash point than 5606 - I had a much harder time inducing ATF to combustion than 5606 when I proved this for myself. It is compatible with the standard seals etc no only by specification but also by empirical evidence. In the world of experimental aviation, this is perhaps one of the "safest" experiments I have performed.

PS: In case you missed this in my previous post:

Flash point of Royco 782 (MIL-PRF-83282) and Mobil 1 ATF appear to be about the same 445F/220C.

http://www.qclubricants.com/royco/royco_782.htm

So unless you're just "very frugal" (I'm being nice here), or just want to be different, there's really no good reason not to use what the brake manufacturers recommend.
 
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Hmm, never been called a coward before for sharing my opinion. Personally I don't really care what you think or prefer to use in your own system, but recommending it to others just because you think it ok is just plain wrong IMO.

I don't believe I ever said anyone should use any specific thing, only that I use ATF. I also don't pretend to be morally superior by claiming to use something just because it's certified and I don't try to install fear of lawsuits for using something else.
 
I don't believe I ever said anyone should use any specific thing, only that I use ATF. I also don't pretend to be morally superior by claiming to use something just because it's certified and I don't try to install fear of lawsuits for using something else.

It has nothing to do with "certified", it's just what the aircraft and brake manufacturers have tested and approved for use in their systems.

It's like the rest of aviation, there are standards we follow in the industry that are considered accepted practices, like manufacturers manuals and AC 43-13, you don't have to do it that way but those are considered "approved" methods of aircraft maintenance and repair.

Can you do it any way you want because it's experimental, sure... but please don't imply I am being "morally superior" because I choose to use accepted aviation materials and practices and not the methods "approved" by some folks on VAF.

Ok I'm done.
 
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Again:

the technician's manual for Parker (Cleveland) brakes says:

Hydraulic Applications - Use fluids compatible with the system
MIL-H-5606 / MIL-H-83282 (Red Oils)
Skydrol ? Only compatible with itself

So...is ATF compatible with aluminum? I'd guess so. Is it compatible with the o-rings? Depends on the o-rings, I guess, but evidence is that it is compatible with the ones we're using. What else is in the brake system for it to be incompatible with?
 
there's really no good reason not to use what the brake manufacturers recommend.

Except ATF is much more available, as several people have pointed out with specific example how 5606 isn't available at their airports...

recommending it to others just because you think it ok is just plain wrong IMO.

Kind of the point of these forums don't ya think? To discuss ideas and learn new things. So long as the points are valid and the discussion is honest, which in this case it seems to be. Welcome to the internet BTW :)

Neither Van's nor any brake manufacturer I'm aware of has tested or approves using ATF in their brake systems, but I guess you're just smarter than they are.

"Hydraulic Applications - Use fluids compatible with the system" Sure seems like at least Cleveland acknowledges there are acceptable alternatives...

Until they do, thank you very much but I'll stick with the "approved" fluids.

That's the spirit! Better to not question things :rolleyes:
 
For what its worth: It was years ago, but I once spent days replacing parts and rebuilding the brake system on a Cherokee 6 that had been operated for a couple months with automotive (Dot 3) brake fluid. Many of the ?O? rings were very soft and gummy...

Yes, DOT 3 is nasty stuff, and I didn't mean to suggest that it's OK to use. Only brought it up because it WAS in use in my airplane and seemed to be working fine (at that moment).

Did a bit of Googling trying to find out the chemical differences between 5606 and ATF and didn't find much. I did find that people are using it interchangeably in automotive lifts, sailboat autopilot systems, industrial hydraulics and other stuff - some of it with claimed manufacturer endorsement of interchangeability.

So I guess if we want to ignore the empirical evidence offered by those who are using ATF in their brakes, a simple test would be in order. Cut a "certified" O ring in half and drop a chunk in a jar of 5606, the other in ATF and let it sit for a while. Once the soak period is over, compare each half and see if there is any sign of distress from the ATF half. Swelling, durometer, and general appearance, should be readily apparent.
 
ATF

I don't know what all the fuss is about on using ATF in aircraft brakes. The O rings are compatible with petroleum based oils. ATF is such; any hydraulic oil will work.

I have been using ATF for over 40 years. An engineer friend used ATF in his 310 Cessna for 35 years. I probably have close to 4,000 hours (different airplanes) using ATF in my brakes. Never had a problem! Thank goodness for experimental aircraft.
 
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