On my 2013 Ford C-max, someone poured brake fluid into the windshield washer reservoir after being told the "yellow cap". Quickly realizing the mistake we disconnected the hose from the reservoir and drained the reservoir. Then we flushed it with large amount of Dawn/warm water and again with warm water.

Do we need to follow up with any other action?

  • I would just put a hosepipe as far into the reservoir as it will go and let the water run for a while.
    – HandyHowie
    Jan 4 at 23:15

1 Answer 1


It happens, usually the mistake is to put window washer in the brake reservoir which is much worse to fix, so if you have to make a mistake your way is better!

Dish soap is fine to clean brake fluid, if the inside feels clean you are good to go. Stick a finger in and feel the inside of the reservoir, if it feels greasy then you still have some residue and you should clean it again. I suggest getting a soapy sponge in there as scrubbing is more effective than rinsing. A sponge on a stick like a bottle sponge works well, I've also used a sponge on the end of a bent wire hanger to get into hard to reach places.

  • Another check is to put water into the reservoir, let it sit for a while, then run it into a clean, clear container. Once in the container you should be able to see what the water looks like. You should be able to detect if there is any brake fluid in the water. Then, pour it out and feel the water to see how it is. The good thing is, when washing with Dawn and water is, since brake fluid absorbs water, it will be attracted to it. I would be the OPs original process has gotten the vast majority of it out. You definitely don't want brake fluid on your windshield! Jan 4 at 14:54

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