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Power steering fluid added to brakes

Major screw up. Added steering fluid to brakes. Drove the car for about 300 miles. Car actually over-heated. Discovered the mistake after. Bleed brakes and added correct fluid. Not heating up now, but only bled the brakes one time. This is on my grandsons 91 Dynasty. Now worried the brakes are going to just go out.

Just bleeding the brakes is not enough. You must completely replace the brake fluid, flush all the contaminated fluid out.

Pay attention to the condition of rubber components in the brake system as they will soften and swell. The first indicator of this would probably be the rubber gasket in the brake master cylinder cap.

It is possible you will end up replacing all rubber components.

This would have nothing to do with an overheating condition.

Yeah, that’s not good at all. Depending on how much braking was done, it may have been possible to salvage the situation if you hadn’t bled the brakes. But bleeding them guaranteed that the power steering fluid got to everything in the brake system rather than just sitting in the master cylinder.

The first thing that happens is that the seals in the master cylinder will swell and block the brake lines, which will prevent fluid from returning to the cylinder. That will lock the brakes.

Then the seals will disintegrate because they aren’t designed to stand up to PS fluid. That will fail the brakes entirely and you won’t be able to stop the car.

Because the PS fluid got all the way through the system, the same thing will happen to anything in the system that is rubber, which means your calipers and rubber lines are shot.

Best practice is to replace the brake calipers, master cylinder, and flex lines. Once you get the flex lines detached from the hard lines, flush brake cleaner through the hard lines to get all traces of power steering fluid out. If any is left in the system, then it will just contaminate the new stuff you install and you’ll end up in the same boat again.

An added problem with the hard lines is that the vehicle is old enough that if you live in a state that salts the roads in the winter, they might be sufficiently rusted that when you go to wrench the flex line off of them, you’ll snap the end of the hard line, which will require replacing that as well. The main difficulty there is in the routing - you can get a cheap line bending pliers at any auto parts store, and they’ll often have pre-flared line in the length that you need so you won’t have to worry about flaring it yourself.

(btw @Bisbonian) I suspect the “overheating” was actually the power steering fluid overheating in the brake system and spilling out of the master cylinder and dripping down onto something hot. PS fluid is not designed to handle the temperatures that brake fluid sees, so it tends to expand enough to overflow the reservoir under enough braking.

Wow. I totally blew it. Might as well sell and get a different car.

Sell it to a junk yard. You do not want to deal with the liability exposure for selling a car with known brake failure to someone who might drive it, wreck it, and then sue you.

shadowfax: Excellent advise on the liability plus having a clear conscience. It reminds me of vintage British vehicles which require Lockheed Girling hydraulic fluid because DOT-3 will swell and eventually dissolve their “live” (natural) rubber seals.

Yep, a '91 Dynasty is not worth enough to solve this problem, and you can’t sell it as-is (at least I wouldn’t).

“Might as well sell and get a different car.”

Clearly, the cost of completely overhauling/replacing the brake system on this 25 year old car would exceed its book value. However…selling it to another individual–even if you disclose a brake problem–would be immoral, as there is a possibility that the individual who bought the car might decide to drive it anyway, either because they don’t understand the true nature of the problem, or because they just don’t care about endangering the lives of others.

The only morally correct thing to do is to have this dangerous vehicle towed to a junkyard.

So most agree that the brakes will just suddenly go out? No warning, no loss of pedal…they just suddenly fail? His father thinks replacing the master cylinder should do the trick. From what I see here …that won’t fix it.


The problem is the power steering fluid could now be in many locations. The brake system’s rubber components (seals) are incompatible with oil-based fluids like power steering fluid. It causes them to decompose, potentially leading to sudden failure.

The first thing you should do if the vehicle is decent transportation for the grandson is call a good brake shop and ask for a ball park estimate to replace fluid and what else they recommend. Just changing the master cylinder and not doing anything else is not a good idea.

Just replacing the master cylinder works if you are just topping the fluid off and put the power steering fluid in and then immediately catch yourself before you use the brakes, because power steering fluid floats on top of brake fluid, so all you have to do is suck the fluid out of the cylinder and then replace it just to be safe.

But once you bleed the brakes with power steering fluid in them, that sends the fluid through every part of the brake system, which means any part of the system that has rubber parts is in danger of failing.

What often happens is that the first indication of trouble is that the brakes lock up. You might be on a freeway and step on the brakes, and they don’t release when you take your foot off the pedal.

At that point, assuming you don’t get rear-ended, they will eventually release after the power steering fluid eats the rubber seals.

Then you think things are OK, because the thing rolls again, and you get in it and drive, and then when you go to hit the brakes the pedal slams to the floor and the car doesn’t stop.

In short, it’s a very dangerous problem to have, and the first warning sign is when your car’s brakes won’t release and you’re just left to hope the guy behind you notices in time – especially since your brake lights won’t be on because it’s the calipers that are stuck closed, and your foot is off the brake pedal.

If the car has 4 wheel anti lock brakes the cost of parts alone will exceed $1,000.