As part of the routine maintenance for keeping your brakes working properly you need to do things like check the calipers, replace the brake pads, and bleed the brake lines. If you head to a mechanic to get this job done, you're probably going to spend somewhere between $75 and $125.
Your brakes run on a hydraulic system. When you put your foot on the pedal, hydraulic fluid is forced through the lines to a piston that's connected to your brake calipers. This pushes down on the calipers and makes them squeeze the pads against the rotor which in turn creates the friction that slows your car to a stop.
In order for this whole process to work, the pressure of your brake lines has to be properly maintained. Any moisture or air that finds its way into these lines is going to affect your brakes for the worst. And this can happen for a number of reasons.
Is Brake Bleeding Necessary?
If you check your owner's manual it's going to give you a recommended time frame for having your brakes bled. In general, you're looking at about every 30,000 miles or so, but your owner's manual will let you know for sure. Your brake fluid is going to potentially develop air bubbles over time that inhibit your ability to properly brake, which can be very dangerous in a pinch.
As you operate your car as normal, your brake pads wear down because of the friction caused by them rubbing against the rotors. This Is how they are designed to work and it's perfectly normal. The calipers squeeze the brake pads against the rotor, friction slows your vehicle down and a small portion of the brake pad is worn off because of that friction. Over time the brake pads will wear down completely and need to be replaced. But before they're completely worn down, they will have lost a significant amount of width. That means you'll have to press your brakes a little bit harder to make up for the amount of space that’s already worn down on the pads. Because the brakes need to squeeze down a little bit more to clamp on the rotors, and there's no extra brake fluid in the lines, what happens is you have gaps created in the system. Those gaps are in the form of air bubbles.
You can also develop small air pockets because, over time, your brake fluid will boil because of the heat caused when they work. As it boils it makes steam and the steam is later compressed back into water again. This whole process causes air to separate and form bubbles in the lines as well, reducing the effectiveness of your brakes overall.
How Can You Tell You Need to Bleed the Brakes?
Aside from changing your brake fluid at the scheduled time, there are a few warning signs to alert you to the fact that your brakes aren't working the way that you need them to and you should consider going to a mechanic and having them bled.
Brakes Feel Soft: One of the easiest ways to tell from the inside of your vehicle when your brakes start to go bad on you and you're going to need to bleed the lines is that the brake pedal itself is going to feel soft under your foot. It's kind of hard to describe if you've never experienced it before, but when it happens, you'll know. Normally there is a degree of resistance from your brake pedal when you put your foot down on it. As air bubbles form in the line you'll find that the brake pedal feels kind of squishy as you put your foot on it. You'll have to press a little bit harder to make it work, and the resistance won't be what you're used to. It's going to feel almost like putting your foot into a sponge.
Need to Pump Your Brakes: When your brakes are working properly you just need to put your foot down once and the pressure should be sufficient to slow your car to a stop. If you find that putting your foot down on the brake doesn't get the job done on the first try and you need to actually pump your brakes several times this is an indication that you're having an issue with air in your brake lines. This is because when you're putting your foot on the brakes those air pockets are preventing the pressure from consistently working to clamp the pads down on the rotors. You need to press the brake pedal several times to work past the air bubbles and get the fluid to apply the correct amount of pressure to the pads and squeeze the rotors to let you stop.
No Resistance: Worse than the issue with soft brakes is when the brake pedal simply stops resisting the pressure of your foot pushing against it at all. This will likely start off as a soft brake issue, but as it gets worse you'll find that the resistance dies away completely and as you put your foot on the brake pedal it just goes right to the floor and it seems like nothing is happening at all. This will typically happen if there is a high degree of air in your brake lines. When you put your foot on the pedal the air pocket is so big in the line that there's nothing to maintain pressure. This is extremely dangerous and can result in your brakes not functioning at all meaning you're at a high risk of having an accident.
If your brakes get to this point while you're driving, then you need to be very careful about how you proceed. Because of the potential risk for accidents and injuries you're going to need to think quickly and carefully about what to do. If you are driving down the highway, for instance, and your brakes are offering no resistance at all, your instinct may be to panic but you need to try to remain calm.
In this case you're going to want to shift down to a lower gear as soon as possible and put your four-way flashers on to alert drivers that you're having a problem.
Keep trying to pump your brakes to see if you're able to build up any pressure. As we mentioned, those bubbles can interrupt the pressure but it's possible that if it's not too bad you'll be able to build some pressure by continuing to pump the brakes. Try it a few times to see if anything happens. If you're not getting any resistance at all, then you may need to try to engage your parking brake.
Obviously, your parking brake isn't meant to be used while you're driving, but this is an emergency situation, and it may be your best choice at this point if there is still no resistance from your normal brakes. Engage your parking brake and using extreme caution try to make your way to the side of the road. Make sure you're signalling and only moving when you're free to do so, nowhere near other drivers so that you're reducing the chance of having an accident. Remember, other drivers don't know why your four-way flashing lights are on, and would have no reason to know that your brakes don't work. They will expect you to brake as normal.
Keep your foot off the gas this entire time and keep coasting for as long as you safely are able to. Hopefully you'll be losing speed during this time. However, if you started at a high rate of speed or you are heading down a hill and actually gaming speed then you may want to gently angle yourselves towards a guardrail or the rough side of the road to help slow your progress. Remember, whatever you're doing, be conscious of other drivers and be as safe as you can until you're able to coast to a stop.
How Long Does It Take to Bleed Brakes?
Getting your brakes bled shouldn't take an inordinate amount of time. In fact, you can probably get all four done in a matter of 30 minutes to 40 minutes at the most. This is potentially the kind of job that you can handle on your own as well if you're comfortable doing auto repairs by yourself.
Step 1: The first thing you need to do is make sure that you have the right kind of brake fluid for your vehicle. There are a number of different kinds of brake fluid available and you don't want to mix the wrong ones. Consider it like coolant and other fluids in your vehicle, if you do mix the wrong ones that can potentially ruin the entire system on you.
Step 2: Once you know you have the right kind of fluid; you need to get your vehicle up on jack stands. When your car is secure, you can remove all four of your tires and get to work.
Step 3: You need to locate the caliper bleeding screws on your brakes. You want to try to loosen this if you can but it's possible it's going to be stuck in place. Don't force it if it doesn't work under a normal amount of pressure because you could cause damage. It is not moving, give it a squirt of some kind of penetrating oil and let it sit for a half hour or so to see what happens. After that you can try it again to see if it comes loose. If they break when you're trying to loosen them, you're going to need to go to a mechanic to get them fixed.
Step 4: If you're safely able to loosen all four bleed screws, tighten them back up again because you want to do this just one at a time. If you have more than one screw open as you're trying to bleed the line, you might get more air bubbles in your system which will cause worse problems.
Step 5: Now you can check the brake fluid levels in the brake master cylinder reservoir under the hood of your car. You need to check your owner's manual if you're not sure where that is. You can add new fluid if the reservoir isn't full. If that's topped up to the level it should be then leave the master cylinder cap screwed on but still in place on top of the reservoir and you can believe each break in sequence. They have to be done in the correct order if you want this to work correctly. The sequence changes depending on the vehicle, so check the manual to know for sure.
Step 6: You need to put a piece of clear tubing over the end of a bleeder screw on the first break and let it drain into a catch container. The catch containers should be higher than the height of the bleeder screw to prevent air bubbles.
Step 7: With the engine off, pump the brakes several times until you feel resistance. Once there is some resistance, keep your foot on the pedal and an assistant can open the bleeder screw a small amount to allow the fluid to drain into the tube and your catch container. Maintain pressure on the brake pedal until it nearly hits the floor at which point your assistant can re-tighten the screw.
Step 8: Top up the master cylinder reservoir with fluid again and repeat the process until the brake fluid streams out with no air bubbles. Then repeat the process again with each subsequent bleeder screw.
Step 9: Once you have done this for every one of your brakes, you can check the fluid in the master cylinder reservoir as your assistance pushes down on your brake pedal. If you notice a lot of movement in the fluid when somebody presses the brake pedal, then you still have some air in the lines, and you'll need to repeat the bleeding process. If there's just a little bit of movement, then you've done a good job, and everything should work now.
The Bottom Line
Keeping your brakes working properly is of the utmost importance to ensuring that you're as safe as you possibly can be on the road. Make sure you're following your owner's manual and its recommendations for bleeding the brakes and if you're noticing any problems with your brakes, make sure you get them fixed before a bad problem gets worse.