Red Fluid on the pedals

[astaib]

Hello,

I noticed yesterday that there is a red liquid pouring in the vicinity of the pedals.
I think that it is brake fluid because it's pouring from the little cylinder on the right hand side.

Can it be that the valve has been badly closed during last annual visit? Or any other trouble?

This liquid is sticky and not very liquid.

See attachment

Any idea?

Thanks!

[astaib]

[Steve]

Arnaud:

Yes, that is brake fluid. It appears to be coming from the fill plug on the master cylinder reservoir (red plastic plug on top). Check to make sure that it is screwed in all the way, and also that the brake fluid level in the reservoir is not overfilled. My recollection is that the fluid level should be about 1 cm below the top of the reservoir. If overfilled, remove some fluid with a syringe and you should be OK. The brake fluid in that part of the system is not ever under pressure.

Steve

[Rich]

A possible cause of this overflow is installing new brake pads.

[astaib]

That’s true I get new brake pads installed lately !

[Davestation]

The solution is that the brake reservoirs aren't supposed to be filled to the brim. Some mechanics mistakenly top them off at some point and when the pads get replaced this happens.

[Rich]

Rather than start a new topic I thought I'd drift this one a bit.

Recently I was checking tire pressures and noted that my left brake was dragging a bit against the disk. It hadn't been obvious when taxiing, but it's not the way it's supposed to work. So I did the simple thing, which was to pull the caliper off and clean up the housing, the slider bolts, etc. so that the parts were free to move. It turns out that wasn't enough. After a flight yesterday as I jockeyed the plane to push it back it made some noise. I found the left caliper was too hot to touch

So I figured it's time to check out the caliper more directly. After checking with my mechanic he advised me it was likely the o-ring that needed replacing. This turns out to be extremely easy and inexpensive to do. Cleveland brakes being widely common he had the required o-ring sitting in stock ($1.00). Pull the caliper off, pop the piston out, replace the o-ring, wipe everything down and put it back on the plane. Really the only hassle was dealing with the hydraulic fluid, as it inevitably drips on anything it comes near and I did have to bleed this brake system, which was easy once I figured out how to operate the pressure bleeder I had yet to put to use.

Here is the diagram and parts list for the DA40 brake calipers (30-239a):

One thing not shown here is that there is a threaded hole in the center of the face of the piston. The threads match the threads of the backing plate bolts (part 15). This greatly facilitates pulling the piston out. Just screw one of these in and pull out the piston.

[Steve]

Rich:

I had to do this a number of years ago too. It was before I had a Power Tow, and had to put the plane into the hangar by hand. Much easier when the brakes aren't dragging...

[Rich]

More on the root subject, this diagram from the AMM shows the range of the air gap in the reservoirs:

I use a pipette to adjust this level.

[astaib]

If I understand correctly this schematic, there is no need to test pilot and copilot brake during ground check, isn’t it?