Accidentally Put Power Steering Fluid In Brake Fluid Reservoir? How to Fix

Since there are several fluid reservoirs under the hood of your vehicle, you might find yourself accidentally putting steering fluid in the wrong place.

The brake fluid reservoir is located above the brake master cylinder, which is typically mounted close to the back of the engine bay. Meanwhile, the power steering fluid reservoir is usually located on the power steering pump or just above it. . It’s typically labeled with “power steering” or “steering fluid” on the lid or it may have a generic symbol for a steering wheel on the reservoir cap. These two reservoirs might seem distinct when described this way, but it can be quite confusing for someone new to DIY vehicle maintenance.

If you put power steering fluid in the brake reservoir, you should be quite concerned. Power steering fluid and brake fluid are completely different and must never be interchanged. Power steering fluid is oil-based while brake fluid is alcohol-based. The oil-based power steering fluid can cause rubber seals and gaskets found in the braking system to swell and rapidly deteriorate, which can cause the entire system to leak and fail.

What that means is that the brakes will lock up and won’t release, and all the components with rubber seals will need to be replaced or rebuilt.

Here are some steps you should quickly follow if you accidentally put power steering fluid in your brake fluid reservoir, provided you catch the error as soon as you’ve poured it in. If you don’t, and the vehicle is driven, it’s usually too late by the time you realize something is wrong.

Don’t Press the Brakes or Drive the Vehicle

Make sure not to press on the brakes as soon as you realize you’ve put power steering fluid in the brake fluid reservoir. When the brakes are pressed, the brake master cylinder will start sending fluid into the brake lines and brake calipers, and that’s when the rubber begins to swell and the calipers lock up.

Removing the Power Steering Fluid

Power steering fluid will just float on top of the reservoir since brake fluid is heavier. If you haven’t pressed the brakes yet, then no power steering fluid has been sucked by the master cylinder and sent to the brake lines and calipers yet. You can still try to skim the power steering fluid using a syringe or turkey baster.

After skimming the power steering fluid, you must purge the brake system. This involves sucking out the brake fluid from the brake lines from the purge valve located on the brake caliper. As the old brake fluid is being drained, you must continuously refill the brake fluid reservoir to make sure the master cylinder doesn’t dry out. You’ll know when you’ve cleared the old fluid when you see the fluid color become lighter.

You must ensure that all the old fluid is removed to prevent brake components like seals and gaskets from swelling. If you don’t remove all the power steering fluid, it might go into the brake system and cause most of the rubber seals to swell.

Cleaning the Reservoir With Brake Parts Cleaner

You need to get rid of all the power steering fluid from the brake fluid reservoir without leaving any residue. Otherwise, the power steering fluid residue might enter the brake system.

You’ll need to remove the brake fluid reservoir and flush it with brake fluid cleaner to ensure that it doesn’t have any more power steering fluid residue.

Reach Out to a Reputable Mechanic

If you realized your mistake late and have already turned on your vehicle and pressed the brakes, then there’s a good chance that power steering fluid has been sent into your brake lines.

The brake master cylinder is capable of thoroughly mixing the power steering fluid and brake fluid and pushing it deep into your braking system. Once the power steering fluid is mixed into the brake fluid, the power steering fluid won’t float to the top anymore.

When this happens, removing the brake fluid in your reservoir won’t suffice. You’ll need to drain all the brake fluid, clean the brake lanes, and replace the affected components. These include parts like the brake master cylinder and brake caliper. This is going to require a lot of work, so it’s best to reach out to a trusted mechanic.