In most cars up until recently, both the braking and power steering systems were hydraulically-based. Under your hood, the fluids may even be a similar color – most likely, some shade of red.
They can look alike, and they’re both hydraulic fluids. So, if they seem so similar, can you use brake fluid for power steering fluid?
Here’s the short answer: no!
This guide will consider the vast differences between these products, but if you’re looking for a quick response, there it is. You cannot use power steering fluid and brake fluid interchangeably.
Let’s get started with the basics.
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What Is Brake Fluid?
Brake fluid is the liquid found within the braking system. It transfers force to the wheels, making the pads clamp to the rotor, applying friction to slow the rotational movement.
Brake fluid works in a sealed series of pipes and hoses. Watch the video included above for a good idea of how such a simple concept is applied to motorcars worldwide. Aside from a few technological inventions, the system has remained essentially the same for decades.
When you push the brake pedal, the servo amplifies the force via some fairly simple physics. The master cylinder, holding the brake fluid, then receives the pressure from the servo and transfers this through the system.
As a result, the pistons in the calipers (rotors) or wheel cylinders (drum brakes) apply the brakes, slowing the car down. When you release the pedal, the system instantly depressurizes, releasing the brakes and allowing the wheels to turn freely again.
Brake fluid is an ethanol-based hygroscopic liquid.
How To Identify Brake Fluid
Like all automotive liquids, it’s imperative to keep the brake fluid above the “MIN” level on the reservoir (and below the “MAX”).
Lift open your hood and find the brake fluid reservoir. It’ll be a relatively small plastic container with a cap. On this cap, you’ll find the required brake fluid type inscribed. The most common example is DOT 4.
You should be able to see through the translucent sides of the reservoir to look at the coolant level. You’ll see the liquid level. Where is it in relation to the “MIN” and “MAX” marks? Anywhere between these is fine, although you may like to top it up so it’s near the “MAX” mark. That way, you can instantly recognize when there’s been a drop and keep the level far away from the minimum.
Brake fluid is a vibrant red when it’s new. Over time, it turns darker and eventually becomes dark brown. When it reaches this state, it’s time to flush the system and replace it all. Provided it’s still a reddish shade, you’ll be fine to top it up.
Ensure you use the right kind of brake fluid! You should find it on the reservoir cap, as mentioned, and also in your owner’s manual. If you head out to an auto parts shop to purchase some, you could also ask the technician to double-check you’re buying the right stuff.
How To Top Up Brake Fluid
You’ll probably find a small filter in the way when you first remove the reservoir cap. When checking the fluid’s condition, it’ll be necessary to temporarily remove this. Replace it as soon as you’ve had a quick look.
Important: when working with brake fluid, you need to bleed the brakes if the level has dropped below the minimum mark. Air could have entered the system, creating a potentially dangerous situation when you start driving again. To bleed your brakes, you’ll need a friend, some basic automotive equipment, a bleed bottle, and some experience. Don’t attempt this by yourself if you’ve never done it before.
With the filter back in place, simply pour the correct type of brake fluid into the reservoir, ensuring you keep it between the marks. Provided the level wasn’t below “MIN”, as mentioned above, that’s all you need to do.
Replace the cap tightly and take the car for a slow, gentle drive around the block to make sure everything’s working. If you’ve made a mistake, it should present itself straight away. Here, it would be time to eat some humble pie and call a mechanic out to your position.
Never drive your car if it’s unsafe to do so.
If the fluid is brown and dirty when you check it, it’s time for a full system flush. While this may be possible to do yourself, it’s a much better idea to take it to a mechanic. It shouldn’t be too expensive and saves you from making a silly mistake and destroying your system (which is possible).
What Is Power Steering Fluid?
The above video is a few minutes long, but it’s well worth watching it for a detailed understanding of how the steering system works and how hydraulic power steering assists you, the driver. The example shown at the start is a hydraulic system. Later, an electric power steering assist version is displayed.
Power steering fluid is what’s used in the power steering system – no prizes for guessing that correctly! Power steering makes turning your wheels much more effortless. You’ll be able to relate if you’ve ever driven a car from the 80s or earlier.
Hydraulic power steering assistance uses a valve between the rack’s pinion and the steering column. The rotary valve regulates the pressure distribution in the hydraulic cylinder encasing the steering rack. These pressure differences in each chamber create the force that assists the driver as they turn the steering wheel.
Without power steering – hydraulic or electric – driving a car is much more of an arm workout. It’s also much easier to lose control of the vehicle. However, some would argue that a complete lack of assistance gives a driver the best connection to the feeling of the wheels and road.
Power steering fluid is created with mineral, synthetic, or vegetable oil. Most newer power steering fluid options are made from synthetic oil. They contain many additives to protect and lubricate the steering system.
How To Identify Power Steering Fluid
First, check if your car uses a hydraulic power steering assist. Many newer models use an electric version that requires no fluid input. In this case, there’s no need to worry. However, most slightly older models and some newer vehicles will require power steering fluid.
You’ll find this information in your owner’s manual. It may be under “power steering”, “steering assist”, or perhaps “regular maintenance”.
The power steering fluid reservoir should be pretty easy to identify. The cap will either have a graphic of a steering wheel on it or a label conveniently reading “POWER STEERING FLUID”.
There are a few different types of power steering fluid, so check (again, using your owner’s manual) before adding anything to your vehicle. ATF, synthetic, and universal are three common types.
Alternatively, head on over to the store (online or in-person) you usually use and enter your car’s registration number. It should automatically filter the results to those your make and model can take – although, again, check!
How To Top Up Power Steering Fluid
Once you’ve located the reservoir, check the fluid level. If it’s low, you’ll need to top it up.
Next, check its condition. You can see the state of the power steering fluid from its color. It should be amber, pink, or clear. When there’s a problem somewhere in the system, it gets contaminated and turns brown or black.
If you notice this, take your car to a mechanic. Not only does the fluid need to be flushed and replaced, but you need to find the source of the problem. It’s probably a cracked or worn O-Ring, seal, or hose – this will also need replacing.
However, if everything looks good, simply add the correct type of power steering fluid to your car. Top it up to the indicated mark. It expands as the engine heats up and you start driving, and too much liquid can do damage in itself.
Replace the cap. That’s all there is to it!
Some might suggest driving without power steering fluid. Yes, this is technically possible. However, controlling the car will be trickier. You’ll also find that the pump, rack, and pinion wear out much faster since they have nothing to lubricate and protect them. It’s best to follow the manufacturer’s recommendations and always keep the levels topped up.
Can I Use Brake Fluid For Power Steering Fluid?
No! Brake fluid and power steering fluid aren’t the same.
As demonstrated here, brake fluid and power steering fluid are two entirely different things. They’re made from different base liquids with vastly different properties and for entirely different purposes.
Brake fluid will not work as power steering fluid. Power steering fluid will not work as brake fluid. In fact, using them interchangeably is almost certain to lead to a crash. At the very least, you’ll damage your vehicle. Badly.
What do brake fluid and power steering fluid have in common? Well, they’re both liquids, used in hydraulic systems, and are often found in a reddy pink color… That’s it.
Continuing along that line of thinking, using brake fluid for a power steering system – and vice versa – will be as useful as pouring in red wine or a pink slushy.
You can’t substitute brake fluid for power steering fluid. Quite honestly, you’d be better off with nothing in a power steering system. Braking systems always need brake fluid – and the correct type, too!
Brake Fluid As Power Steering Fluid – Conclusion
Brake fluid can’t be used as power steering fluid. It would be beyond futile, and you’d need to take your car to a mechanic to have the liquid removed and replaced with the proper stuff. You’ll be fine to drive there if you go straight away and the shop’s local.
What would happen if you did pour brake fluid into the power steering fluid reservoir? Well, as mentioned, you immediately take the car to a technician (you’ll be fine to drive there if it’s immediate and local). You’d see the following results.
- Unlubricated steering parts and unnecessary wear and tear.
- Damage to the rubber seals and O-Rings within the system – brake fluid is corrosive
- Damage to the power steering pump – no lubrication.
In short, simply go out and buy some power steering fluid. Make sure it’s the right type for your car and pour it in. It’s as simple as that and not likely to cost more than $20 or so. It’s an incredibly simple job and won’t break the bank.
Please don’t be lazy. Use power steering fluid for the power steering system and brake fluid for the braking system. It might save you hundreds – if not thousands – in potential future repair bills.
In answer to this article’s question? You can’t use brake fluid for power steering fluid!