Brake fluid.?

Question

Why is it that the brakes on cars need to be "blead"

I know the answer is to get rid of the air within the brake system.

My question is how does air enter the brake system when it is enclosed and there is no way air can get in?What causes the air bubbles?

Answer 1

Air can get into the system if your fluid level gets too low because the brake pads are wearing. As the pads wear the more fluid must go into the lines. Many people do not pay any attention to their brake fluid level until the brakes need replacing, and by then they can have air in the lines.

Also, if the brake cylinder seals are worn and leak fluid when you apply the brakes, they will also leak air in, when you take your foot off the brake pedal. This air pocket will build up in the lines where they connect to the cylinders.

Answer 2

It is moisture not air that isd making it need bleeding. Air cannot get in.

Moisture may be introduced into your brake system, and brake fluid will absorb it to prevent corrosion: but this also makes the fluid less effective. Bleeding the brakes should be done every other year, or any time you suspect diminished brake performance and have verified the remainder of the system is in optimal condition.The only way air gets in is if you let it in manually by messing with the bleeder valves letting the fluid tank go below the line.

Answer 3

Air does not enter a system without opening a line. What you are referring to is moisture in a system. To elaborate on this you need to distinguish what type of fluid you have. You will only have what you are describing happen with DOT 3 brake fluid. It is a mineral based fluid that absorbs moisture. With DOT 5 brake fluid it is a synthetic based fluid that does not absorb moisture. DO NOT MIX THE TWO unless you want to replace every component in your brake system. Hope this answers your question.

Answer 4

Too much air in the brake system will allow too much compression and your brake pedal will hit the floor before you get up enough pressure to stop effectively.

(Most liquids don't change volume (for all practical purposes) with changes in pressure.)

In addition to the above responses, air can enter the system anytime the fluid in the master cylinder is too low.

Answer 5

Services centers call it "Brake fluid change & bleed system" for a reason. You don't bleed it because of moisture filled fliud, you bleed it to remove air that was caused by removing the fluid wrong but more so changing out a brake part that let air into the system.

Now you change the fluid because moisture filled the fluid :)

Answer 6

Air usually only gets in the system if you change the master cylinder, brake calipers, or brake lines. If you properly bled your brakes when they were installed, then there should be no reason to bleed them further.

Answer 7

Air CAN get in but that would be due to incorrect 'bleeding of the moisture or air causing the 'spongy' feeling you may feel...