Brake Bleed
What is the brake hydraulic system?
Nearly all passenger vehicles use the very reliable hydraulic brake system. At a minimum, the system is composed of a master cylinder, which pumps brake fluid through brake lines, wheel cylinders or brake calipers that actuate the brake pads or shoes, and brake rotors or brake drums that rotate with the wheel until acted upon by the pads or shoes. In order for the brake system to function properly and reliably, the brake fluid must be serviced regularly, including flushing and bleeding the brake fluid to prevent corrosion, air, or water from causing damage in the brake system.
Which should I get, a brake fluid bleed or a brake flush?
The brake bleeding process involves manually pumping enough new fluid through your brake lines to eliminate any air that may be in them. This can be done either by one person, using an external hand pump, or by two people, using the car’s brake pedal. The vehicle’s four brakes are bled individually, using a bleeder screw found on each caliper or wheel cylinder. People with good knowledge of hydraulic braking systems can learn how to bleed brakes themselves, or a mechanic can handle it instead.
The brake flushing process goes a step beyond. Flushing replaces all of your old brake fluid with clean, new fluid. This procedure is often done with a powered flushing machine, which attaches to the brake fluid reservoir where the cap would normally screw on. New brake fluid is forced through the entire hydraulic system until the fluid that exits the system is clean. Flushing gives you all new brake fluid throughout your braking system.
Here are a few guidelines on whether you should bleed or flush your brakes when servicing them:
What does the manufacturer recommend? Check your owner’s manual or service booklet for the manufacturer’s suggestions on when and how to service your brakes. If there’s no recommendation for flushing your brakes, it’s usually not necessary, especially if you have followed the recommended service intervals and the fluid looks translucent or clear, not dark and murky.
Are there signs of a braking problem? Have you noticed that your brake pedal feels squishy? Does your vehicle require a longer distance to stop lately? Is your brake fluid dark, or does it have particles and debris floating in it?
If you notice any of these symptoms, get your car to your mechanic immediately. Have your braking problem diagnosed and repaired right away, before things get worse and you are totally unable to stop. If your fluid has deteriorated and needs replacing, then a flush is an appropriate step toward restoring the effectiveness of your brakes.
What are symptoms that may be fixed with a brake system bleed?
The most common cause necessitating flushing and bleeding brake fluid is a standard brake service. However, if the fluid is noted to be extremely old, dirty, and hazardous to rubber brake system components, a flush and bleed service should be completed. Also, when there is a brake fluid leak, this service will be completed to remove air from the system. Lastly, if the brake pedal feels too soft or spongy, and the service brakes are not performing to standard, the brake system will be bled and flushed to eliminate air from the system. This will be performed after verification and repair of the source of air.
Can I drive if I need a brake system hydraulic system bleed?
It is not safe to operate any vehicle with any braking problem. If there is any sign that the brakes are not performing as originally intended, the vehicle should immediately be placed out of service, and repaired. If the brake fluid is being flushed and bled as part of routine maintenance, with no symptoms noticed, the vehicle can safely be driven to a repair shop.
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How often does a brake hydraulic system bleed need to be performed?
Service of the brake system is part of factory scheduled maintenance, and the schedule is located in the owner’s manual of most vehicles. Most brake services are performed between 40,000 and 60,000 miles, and the brake fluid will be flushed and bled at that time. Notice, failure to adhere to factory schedule maintenance guidelines may result in premature failure of various brake system components.
How are brake hydraulic system bleed issues diagnosed?
Brake fluid bleeding requires no diagnosis. It is performed at the completion of a repair, as part of a brake system flush, or as a step in testing the brake system if a diagnosis requires.
RepairPal Recommendations for brake hydraulic system bleeding
Many dishonest shops will recommend these services before they are due, when not performing a brake service, and at the expense of the owner. Any time you feel the service is not warranted, ask why it should be performed now and consider contacting one of our certified repair facilities for a second opinion. If you are completely uncertain, you can always ask us for advice here on RepairPal.com.
What to look out for when dealing with brake hydraulic system bleeding
During a scheduled brake service, the fluid is normally changed and bled. This is because technicians understand the necessity of releasing brake fluid from the brake calipers and wheel cylinders to prevent damage to anti-lock brake components by pushing fluid or debris into the ABS module. When this is done, the fluid may appear clean and clear, but if the factory recommends changing, the best course of action is to follow that guidance.
Can I perform a brake system hydraulic system bleed myself?
The braking system can be maintained by a DIYer with a complete knowledge of hydraulically actuated systems. This is important as testing brake operation, and safely servicing braking components rely on this knowledge. If the complete braking system is not understood, damage to the expensive braking components, or injury is likely. Especially when poor braking performance is the symptom, failure to perform this task can lead to a collision. Trusting a professional technician with the replacement of any braking component is normally the best course of action.