2013 Prius Brake actuator/pump issues - is DOT4 Brake Fluid an easy fix for this problem?

there may be an extended warranty, but you need a trouble light/code.

i've read that changing the fluid can sometimes help reduce noises in the valves, but nothing about repairing leaks.

 

That's probably getting the cause and effect shuffled a little bit.

Failure of components inside the master cylinder assembly is most likely the reason your pump is cycling so frequently. (By the way, how frequently is "frequently"? If the leaking is fast enough, you can probably hear it with a mechanics' stethoscope, and know for sure which of the two assemblies the leak is in.)

So it is probably too late to find a way to not need the actuator assembly.

It might be possible, though, to get that sorted before the pump has also been worn out from having to run so often, and at least avoid having to replace both. (On top of being more money in parts, that would be more labor; access to the pump is a bear.)

 

Doing a brake flush can fix it for a few days by eliminating nitrogen or air in the lines. Then it will return.

 

Repair of failing brake components (I won't even attempt to name those components) aside, the spec'd fluid is DOT3. Also, while Toyota USA says nothing on the subject, Toyota Canada says to replacef the fluid tri-yearly or 48K kms, whichever comes first.