I accidentally put power steering fluid in with brake fluid

Flushing makes the problem much worse. The only way this could have been solved inexpensively is if the wrong fluid could be sucked out of the reservoir right away, but it's most likely too late for that. The only other exception would be if you drained the brake fluid right away, as within a few hours. If that is the case, the only acceptable thing to flush the system with is more brake fluid.

Brake fluid is a glycol product and all the rubber seals and other parts are compatible with brake fluid. They are not compatible with petroleum-based products. That includes engine oil, transmission fluid, power steering fluid, wheel bearing grease, and penetrating oil. As a brake system professional, I even washed my hands with soap and water before assembling parts I was rebuilding to prevent getting fingerprint grease on the rubber parts.

By draining the system, the power steering fluid was sent down to all four wheels, so the entire system became contaminated right away. Every year I performed an experiment so my students could see whet happens with contaminated brake fluid. I had two beakers partially-filled with fresh, clean brake fluid. I put a new rear brake wheel cylinder lip seal into both, then added one drop of engine oil or power steering fluid to one of them. Exactly one week later the seal in the contaminated fluid had grown about 25 percent and was real soft and slimy. I washed that seal with brake parts cleaner, then after a few days it had shrunk back down quite a bit, but still felt mushy and gooey. The same thing happens in the master cylinder. There's four rubber lip seals in there. When the two primary seals swell, they grow past the fluid return ports and block them. Then, as the brakes heat up, the brake fluid expands but it can't flow back up into the reservoir, so it applies the brakes harder. That builds up more heat, and the fluid expands some more. Before long the brake will be smoking and it will be hard to get the vehicle to move. An additional clue is the brake pedal will be higher than normal and feel harder than normal. There are other, simpler causes of dragging brakes, but every time we hear that complaint, contaminated brake fluid is the first thing that comes to mind.

If we're past the first few hours where flushing may still be acceptable, the only proper repair is to remove every part that contains rubber that contacts the brake fluid, flush and dry the steel lines, then install new parts and refill the system. That includes the master cylinder, front calipers, rear calipers or wheel cylinders, four rubber flex hoses, combination valve, and height-sensing proportioning valve, if used, (that's mainly a minivan and truck thing). A car as new as yours is likely to also have optional anti-lock brakes. If it does, the hydraulic controller must also be replaced since it contains rubber seals and gaskets. Even without that controller, the cost of parts can result in older vehicles being not worth the cost of repair. If any rubber part is not replaced, the contamination will leach back out of it and recontaminate the new brake fluid.

I described the best case and worst case. Many people will try to cut corners, and they often get acceptable results. The difference with a professional is they won't risk their reputation or a potential lawsuit by trying to save a few bucks. Even if it takes months for a problem related to the contaminated fluid to show up, you can be sure if there's a crash and a lawyer or insurance investigator gets involved, the person who did the work is also going to be involved. Even if the other guy ran a red light, a good, . . . well, an effective lawyer will convince a jury you were partly at fault because you were less able to avoid the crash, and he will be right.

Once all the rubber parts are removed, Brake Parts Cleaner can be used to flush the steel lines. That gets blown out with compressed air. Refilling the system with new brake fluid is pretty straight-forward, unless the car has anti-lock brakes. The hydraulic controllers have multiple chambers where air gets trapped. That air causes a low and mushy brake pedal. There are some systems where you can ignore those controllers and bleed the brakes like we've always done since just about forever, but the majority of ABS hydraulic controllers require the use of a scanner to get the air out of those chambers. Some of the internal valves have to be switched on and off to expel the air. Those valve can be operated by forcing the vehicle into a skid, but the bleeder screws have to be open at the same time so the air-laden fluid has a place to go. The car can't be driven with open bleeder screws. The scanners have a very quick, simple procedure to solve that. Once connected to the car, the procedure takes all of three or four seconds for each of the two halves of the system.

The same problem occurs if you're trying to flush out the contaminated brake fluid with new fluid. The contaminated fluid in those chambers will be stuck there. The new fluid will just flow past those chambers without washing out the contaminated fluid. Here again, the scanner with its bleeding procedure will allow that contaminated fluid to be pushed out so it can flow down to the wheels and out.

Here's links to some dandy articles that can provide more information:

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

https://www.2carpros.com/articles/brake-caliper-replacement

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

https://www.2carpros.com/articles/how-to-replace-a-wheel-cylinder

If you drained the contaminated brake fluid right away, or within a few hours, chances are the rubber parts are not contaminated yet. It takes more than just contact with the petroleum product. It takes time for that to work its way into the rubber. If this is the case, run only fresh, clean brake fluid through and bleed it out at all four brakes. I would suggest buying a quart bottle of new fluid. Run half of it through, then discard it. Don't try to run the same fluid through multiple times. Let the wheels gravity-bleed until system is empty, then refill with more new fluid and bleed at the wheels as normal. If the brake pedal doesn't feel as high and solid as normal, you'll need to visit a mechanic with a scanner to bleed the ABS hydraulic controller.

Please let me know how long the brake fluid has been contaminated and how you'd like to proceed. I've been involved with three cars with contaminated brake fluid including a '59 Edsel I bought at an auction.

I would not risk reusing the master cylinder. It also doesn't pay to buy a rebuild kit for it as they often cost more than a professionally rebuilt unit with a warranty.

If no brake fluid was bled at the wheels yet, there's a good chance the power steering fluid hasn't made it down that far. Each time the brake pedal is pressed, brake fluid goes roughly six the ten inches down the lines, then it rushes back up when the pedal is released. Each time the contaminant creeps down a little further. If that 20 miles was all city driving, I'd expect the power steering fluid to have reached the front calipers, so at a minimum, those calipers and their two rubber flex hoses should be replaced. If you have anti-lock brakes, replace the hydraulic controller too. I know it's an expensive part and it is possible the contamination hasn't made it that far, so it's up to you if you want to chance it.

I do have a trick you may consider when it comes to replacing the master cylinder. This works best on GM and Chrysler products because only two steel lines come out of it and they're on the same side. Fords often have four lines connected to the master cylinder. This still works, but it's a little messy.

Use a flare-nut wrench, aka "line wrench" to loosen the soft metal nuts that hold the lines to the master cylinder. Remove the nuts that hold the master cylinder to the power booster. Pull the master cylinder forward off the studs, then use it as a handle to bend the steel lines upward a little. That will prevent brake fluid from running out of the lines. Finishing removing the lines, then remove the master cylinder. Brake fluid will be dripping from the ports. That will eat paint so be careful to protect the area. Wash any spilled brake fluid off right away with water.

Bench-bleed the new master cylinder. That's described in the article, but I can answer other questions if necessary. The new master cylinder comes with two plastic inserts and two rubber hoses for the bench-bleeding procedure. Leave them in place as you carry the master cylinder into the engine bay. Now remove them one at a time and install the lines. Snug is good enough for now. Use the master cylinder as a handle to bend the lines back down, then bolt it to the power booster.

You'll need a helper for this next step. Loosen one of the line nuts about a quarter turn, then have your helper push the brake pedal very slowly. It should take about ten seconds to go halfway to the floor. You'll see air bubbles squirting out around the line nut. Snug that nut, then holler to the helper to release the pedal. If the pedal is released before the nut has been tightened, air will get sucked in and you'll have to keep doing this over and over.

Loosen the nut and do this a second time. If you see a few air bubbles spurting out, do it a third time. Tighten that nut, then do this same procedure for the second line. When you're done with both, or all four, there will still be a few tiny air bubbles stuck in the lines. Don't worry about those. They're way too small to affect anything, and as you drive the car, when you're holding the brake pedal at a red light, those bubbles will gradually float back up. When the pedal is released, those bubbles will wash into the reservoir along with the brake fluid that's rushing back up.

With this trick, I never had to bleed at the wheels when replacing a master cylinder. For your car, however, we have to consider there's still power steering fluid in the lines. This trick prevents air from getting in the chambers in the ABS hydraulic controller, so you won't need the scanner, but I would still bleed at the wheels until nice clean, clear brake fluid comes out. The cost of that brake fluid is cheap insurance that no contamination is left in the system.

Also, as a point of interest, every manufacturer specifies a regular interval for changing the brake fluid, but since the systems cause such little trouble, most of us aren't even aware of that. Brake fluid loves to absorb moisture from the humidity in the air, even through the porous rubber hoses. Besides leading to corrosion, water lowers the boiling point of the brake fluid from well over 400 degrees to closer to 212 degrees. Under common driving conditions that water can boil and vaporize leading to one form of brake fade. This is an age thing, not a mileage thing. We can justify replacing your brake fluid even if it had never been contaminated.

For my last comment of value, watch out for anyone who tells you to push the brake pedal all the way to the floor during any bleeding procedure. You'll even see it described this way in manufacturer's service manuals. This warning does not apply to any new or rebuilt master cylinder being installed, or any that are less than about a year old, but it's still a good practice to follow. Crud and corrosion build up in the lower halves of the bores in the master cylinder where the pistons don't normally travel. When the brake pedal is pushed all the way to the floor, the rubber lip seals run over that crud and can be ripped. That leads to a slowly-sinking brake pedal when steady pressure is applied, as in when sitting at a red light. That damage commonly doesn't show up until two or three days later. Even some very experienced brake system specialists don't believe this can happen, but I've repaired at least a dozen cars and trucks for this. Most were from someone doing a standard brake job. There was no history of a low brake pedal until right after the brake service. Best practice is to always pretend there's a block of wood under the brake pedal, and never push it more than halfway to the floor. Again, this doesn't apply to a new master cylinder because there's no corrosion built up in it yet.