Dot 4 Brake Fluid

[robcaldwell]

Is this what most are using?

About how much to fill an entire system on a 4 Place with both left and right brakes?

[Archer39J]

Not sure about DOT 4. Folks who fly RVs seem to like Mobil1 ATF for some reason: http://www.vansairforce.com/communit...d.php?t=148051

[Rollie]

I guess you can use whatever you want but might want to check compatibility of brake fluid with the seals and lines. I just used 5606 hydraulic fluid like every certified plane I have ever flown. I don't think you can buy less than a quart and that is way more than you will need. I think ATF is pretty similar but I really don't know, maybe its just the same color.

[Bdflies]

I’m with Rollie. 5606 is all I've used. Any airport that has any level of support services will have 5606, meaning that you’ll be able to top off if needed. Don’t know what would happen if you put 5606 into a system having DOT 4. I do know of a guy who bought a 112Commander and topped his brakes with DOT 3. He got to do a total rebuild of his brake system.
DOT 4 is a "silicone" fluid. I’m sure someone here will know about compatibility issues.

Bill

[tailwind]

5606 brake fluid is simply a hydraulic fluid that has been produced to a government standard. Standard number 5606. Many hydraulic fluids meet this standard. Modern automatic transmission fluids meet or exceed this standard. The military has now gone on to use a new brake fluid that far exceeds the flash point of 5606. My concern with dot 5 would be compatibility with the seals in the system. Dot 5 is non-hygroscopic, will not absorb water. The problem with earlier automotive brake fluids is that they did absorb water and caused corrosion and problems with seals and hoses requiring a flush and rebuild of the brake system.
Having said all of the above I have run automatic transmission fluid in two aircraft. In the 4 years of operation with this plane I have yet to need to add fluid. You could get the same result with 5606 but I can purchase automatic transmission fluid at my local store and I don’t need to pay shipping. Just one more positive for owning and flying an experimental aircraft.

[Ed.Meyer]

We use Mobile 1 ATF. No problems and the advantages mentioned above.

[Archer39J]

FWIW I also will be using ATF in the brakes.

[Battson]

You need bugger all of the stuff, a few hundred mL would be heaps. Get a re-sealable container if possible, you will have leftover fluid and the air will degrade it in time.

I just used a MIL-SPEC compliant one from the local store, to ensure the fire risk was managed.

[S Lathrop]

My experience with brake fluids is a bit dated but for what it is worth, here is what I learned years ago from auto racing.

The off the shelf , auto parts store brake fluids were/are about 15% water soluble. For every 1% of water the boiling point of the fluid went down 10F degrees. In the race cars I was working with that was a problem. Preparation for each race included bleeding the brakes. It was done mainly to change the fluid. So that was never a problem. And I always used a new can of fluid.

When silicone brake fluids were the new, hot stuff, I tried them. But it was impossible to keep air out of the system, no matter how diligent we were bleeding brakes. The best I could figure was that as the pistons retracted, some small bit of air would come back with the piston and after 30 minutes to an hour on the track, the brake pedal would go soft. Bleed the brakes and sure enough you would get significant air and the brakes worked fine for a while. That ended my using silicon brake fluids.

Using ATF seems like a very good option. If seal compatibility is not an issue.