One of the more overlooked things that you need to get done in your car is having your brake fluid flushed. Everyone knows that oil changes on a regular basis are a good idea but your brake fluid needs to be maintained as well and it's only going to cost you between $80 and $200 to get it done, on average.
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The cost of a brake fluid flush depends on where you live and also the kind of fluid that you're having put into your car. Just like with motor oil some brands and formulations will cost much more than others. And of course, as with any repair, one mechanic on the far side of town may charge nearly twice as much as a mechanic on the other side of town. It's always a good idea to call around and get some estimates before you commit to anything so you can find out if you're going to get the best service at the best price.
What Does Brake Fluid Do?
The brakes in your car will not work without brake fluid because it is a hydraulic system. That means that it works based on the pressure of liquid in an enclosed system. This is why if a brake line is damaged, the brakes fail. The hydraulic pressure is no longer able to maintain the system. When you put your foot on the brakes, there's no pressure, the brakes are unable to function. As you can imagine, this is one of the most important things in your entire car. If your brakes fail, you and everyone else around you are in extreme danger.
Normally when you step on the brakes, pressure forces the fluid down the line causing the pads to depress against the rotors which in turn causes the car to slow to a stop.
Most brake fluid on the market today is a glycol ether-based formula. You can also get silicone-based formulas and mineral oil-based formulas. It's important to know if you plan on replacing the brake fluid yourself, you absolutely cannot mix these kinds of brake fluid together. They don't work together properly and will definitely damage your vehicle.
Types of Brake Fluid
There are several types of brake fluid that you can buy, and not all of them are going to work well in your vehicle. You need to check your manual so that you know what kind of brake fluid is meant to go in your car. Mixing the wrong fluids together could be disastrous.
DOT3: This is a glycol-based fluid and has a lower boiling point than DOT 5, for instance. DOT3 and DOT4, because they are glycol based, are able to absorb water either from the air itself or from leaks in the line. For that reason, you need to keep your brake line sealed at all times to avoid contamination. The more water that gets absorbed by the glycol, the lower its boiling point gets, and the sooner it can fail on you.
The boiling point of DOT3 fluid, what they call the dry boiling point, is 401 degrees Fahrenheit. That means that pure DOT3 brake fluid will boil at that temperature. The wet boiling point, which is what happens when it has absorbed water, is nearly half the dry point at 205 degrees Fahrenheit. Your fluid is considered wet if it's only 4% water. This is a very common type of brake fluid and will work in most vehicles.
DOT4: DOT4 brake fluid is almost the same as DOT3, but there have been additives included to alter the boiling point. DOT4 fluids are also fairly standard for most average vehicles, although you can get a super DOT4 that is designed for performance vehicles like race cars. It can handle much higher temperatures, but it will need to be changed more frequently. There's absolutely no reason to use this in a normal car, however. The difference between DOT3 and DOT4 isn't very significant, but your owner's manual will tell you which one your car is supposed to be using.
DOT5: DOT5 brake fluid is not compatible at all with DOT4 or DOT3. DOT5 is a silicone-based brake fluid, and as such it doesn't absorb water at all. That means it has a higher boiling point, but it also means that if water does get in the line it will be in a pocket, so as it pushes through it could cause your brakes to corrode. DOT5 brake fluid isn't better than DOT3 or DOT4, it's just different. It's also more expensive, and less common, so it's very unlikely that you would need DOT5 brake fluid.
DOT5.1: DOT 5.1 brake fluid is not the same as DOT5, despite the name. It's another glycol based one like DOT3 or DOT4, but the boiling point is similar to DOT5.
What is a Brake Fluid Flush?
Over the course of a year, your brake fluid will absorb 3% of its own weight in water. On top of that, as you drive and use your brakes, little bits of metal or rust will slowly contaminate the brake lines just as a part of regular everyday wear and tear.
A brake fluid flush bleeds the line of the old fluid, debris, water, and any gas bubbles that have formed. Old brake fluid is typically dirty and dark in color while new brake fluid is clear and yellowish in colour. The process of flushing the system involves draining all the fluid inside of the reservoir and then jacking your car up, removing the wheels and connecting a tool to the brake valve to force out the remaining fluid before adding new fluid. Your mechanic will go brake by brake doing this until only clean fluid is present in all the lines.
Signs That You Need a Brake Fluid Flush
There are few signs but to look out for that indicate your brake fluid needs a change and you should get your lines flushed.
- Low Fluid Levels. You can see your brake fluid reservoir by just giving a visual inspection under the hood. The location varies depending on the vehicle, but it's likely somewhere on the driver side near the firewall. Check your manual to find out for sure. You should be able to see if it's full or if the fluid levels are low.
- Veering When Stopping. If you find your car pulling to one side or the other every time you brake, it's possible that your brake fluid is low and your brakes aren't working evenly as a result, causing you to veer off in one direction or another.
- Dirty Brake Fluid. Even if the brake fluid levels in the reservoir aren't low, if it looks like old motor oil then it's heavily contaminated and will need to be replaced.
- Spots on the Driveway. This one is harder to identify for most drivers as there can be a number of different fluids that leak from your vehicle. But if you are able to recognize spots of brake fluid on the driveway then clearly you have a leak in the system somewhere. There are a number of hoses and gaskets that could wear down over time and cause the system to break down. If you have a definite leak it needs to be addressed right away or else your brakes may fail at a crucial time.
How Often Do You Need a Brake Fluid Flush?
As with everything in your car, the longer you drive it the more likely it will be to require maintenance. Most mechanics recommend a brake fluid flush every 30,000 miles or every 2 years.
Vehicle manufacturers will have different recommendations for when this is best, however. For instance, Chevy tends to recommend a brake fluid flush every 45,000 miles. On the other hand, Mercedes will recommend every 20,000 miles.
It's always good to follow your manufacturer's recommendations for maintenance whenever possible as it will allow your car to run at optimal conditions. That said, a number of major manufacturers have no recommendations whatsoever for how often you should be flushing your brake fluid. Neither Ford nor Toyota, for instance, have any official recommendations on when you should be flushing your brake lines.
Brake Fluid Flush DIY
It's very unlikely that you can do a full brake fluid flush on your own unless you have access to a lot of professional mechanic equipment. If that's the case, you wouldn't be asking the question about whether or not you can get this job done.
While it's possible to do a fluid swap in your car, a full flush is likely beyond your skill and ability as an average car owner. As we mentioned earlier, if you want to do a full flush of the brake system you're going to need to raise the car up, remove the tires, and introduce a pressurized pump to actually force all the old fluid out as you introduce new fluid into the system. This is a fairly in-depth procedure, and you need a professional mechanic to do it.
What you can do at home, and this is only a stopgap measure, is a fluid swap. You can either refill a low reservoir with new brake fluid, or you can clean out some of the dirty old brake fluid and swap it out with new clean fluid. This isn't a perfect fix, but it is a Band-Aid solution to help improve your overall performance.
Brake Fluid Swap
If you do a fluid swap, you will need something like a turkey baster, as odd as that sounds. You can use this to get down to the bottom of the reservoir and suck out the old, contaminated fluid. The heavier, dirty brake fluid will settle to the bottom, so this will make it easier to get out.
You can suck out as much as possible with the baster, and then replace it with new clean fluid. There are a couple of very important factors you need to consider if this is something you want to try.
First and foremost, you need to make sure you have the exact right brake fluid for the job you're doing. As we mentioned earlier, you need to find out if your car is running with DOT3, DOT4, or DOT5 brake fluid. These cannot be mixed, or they will not work properly. And since you haven't done a complete flush, you will end up mixing different fluids together.
If you're confident you have the exact right fluid, you need to work quickly as well. Unless you're using DOT5 silicone-based brake fluid, then the glycol-based fluid that you're using will absorb moisture from the air. You never want to leave your brake fluid reservoir open for very long, nor do you want to have a bottle of replacement fluid open for very long.
When you're ready to do a fluid swap, you need to move as quickly as possible and empty the bottle into the reservoir. You will likely have to repeat this procedure several times over the course of a couple of weeks, driving frequently in the interim to allow the new fluid to circulate through the system.
Fortunately, brake fluid itself is actually very cheap. You can get AutoZone's own brand of brake fluid in a 32oz bottle for only about $6. You can see why some drivers might choose this as an alternative to going to a mechanic to have the entire system flushed.
At the end of the day, a full system flush is the most efficient way to ensure that your brakes are working as well as they can. As well, your mechanic should be able to inspect your rotors, pads, and calipers at the same time to make sure that there are no other problems with your brake system.
Brakes are arguably the most important safety feature on your car, so you never want to take them for granted, and you never want to cut corners when it comes to safety and maintenance. If you know what you're doing and your confidence in the outcome feel free to try a fluid swap. If not, we strongly recommend going to a mechanic and paying the $100 to $200 to get your brake system flushed properly. You never want to take chances with your safety, or the safety of others.