1998 Ford Explorer



July, 13, 2011 AT 6:06 AM

Accidentally put power steering fluid in the master cylinder (the brake thingie) and the brakes are mushy do you have to bleed the brake lines to get it out?

I found conflicting answers which is correct?

"They are both hydraulic fluid so you won’t destroy the whole system like some of these people said… you still need to have it flushed and filled with the proper fluid ASAP though. It will hurt nothing. If the question was reversed, you would have a problem. Brake fluid is corrosive…not power sterring fluid."

"Power steering fluid will cause the rubber parts in your brake system to swell up. Flush out the power steering fluid, and just to be safe, change your brake hoses."


4 Answers



July, 13, 2011 AT 6:51 AM

The first response is WAY off base. If that were my employee and my explanation didn't satisfy him, he'd be fired! The second response is correct. To put it another way, ... You got junk! Brake fluid is a glycol product. The rubber parts used in the system are absolutely not compatible with petroleum products such as power steering fluid, engine oil, or automatic transmission fluid.

There is only one proper repair. That involves replacing every part that has rubber parts that contact the brake fluid, and flushing and drying the steel lines. That means the front calipers, rear wheel cylinders, all rubber flex hoses, master cylinder, combination valve, and the reservoir cap if a new one doesn't come with the master cylinder. If any of those parts are not replaced, the petroleum product will leach out of the contaminated parts and recontaminate the fluid.

To prove to my students how serious this is, every year I placed a pair of wheel cylinder lip seals into a pair of beakers with about an inch of new brake fluid. In one I added one drop of engine oil or power steering fluid. By the end of the week the seal in the contaminated fluid had grown by about 25 percent and was real mushy.

I've been personally involved with three cars with fluid contamination. It's a real big headache. If your vehicle has anti-lock brakes, you might consider sending it to the junkyard. The hydraulic controller is very expensive and is full of rubber seals and o-rings. Also keep in mind the front calipers and rear wheel cylinders are made from cast iron which is porous. We used to always rebuild those parts during regular brake jobs. Today rebuilt calipers and new wheel cylinders are very inexpensive. Don't try to rebuild those parts because contamination can leach back out of the cast iron. If you try to save money by thinking the contamination hasn't reached some part yet, you'll be chasing problems for the rest of the life of the vehicle.

Another sad tale happened in the mid '80s at a Sears Auto Center. Someone used a funnel that had been used for engine oil to fill their pressurized brake bleeder ball with three gallons of new brake fluid. They wiped the funnel clean but didn't use any cleaning chemicals like brake parts cleaner. The very little residue in the funnel contaminated the entire three gallons of new fluid, and caused brake problems that they had to repair on dozens of cars before they figured out the problem.

Whoever posted that first response should be strung up by his lips!



July, 13, 2011 AT 10:12 AM

I agree with Doc 100%. This is a major problem and will go on forever if not repaired correctly the first time. The guy that gave you the first answer has no clue.



July, 13, 2011 AT 7:22 PM

Hi Wrenchtech. If you look at the second response, it ain't so great either. Flush, and MAYBE replace the hoses, just to be safe? I overlooked that the first time. Guess I was too focused in the first response.



July, 13, 2011 AT 7:57 PM

Yeah, me too..
Have to replace anything with rubber inside and then flush.

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