Tip & How-To about Miscellaneous

Brake system flush / bleeding

Brakes overheating: The heat of the system causes the air in the system to expand more than brake fluid and it actually applies pressure to the brakes as you warm up the vehicle. The more you drive the worse it gets and sometimes will cause a wheel to lock-up.

If you replaced the master cylinder make sure you bench bleed it before installation or at least prior to connecting the brake lines in the vehicle.

To properly flush or bleed the brake system:

During this entire process, do not let the master cylinder reach the bottom or you have to start over. Check before each attempt to bleed the brakes. Refill at the 1/2 way mark or close.

Before starting, you should cautiously fill the master cylinder to the full amount and re-install the lid on the brake fluid and the master cylinder to limit splashing (air gets into the fluid) during the bleeding operation. This is a 2 person operation.

First, to get all of the air out you must start at the wheel farthest from the master cylinder, the Right Rear! After breaking the bleeder valve loose but still not letting brake fluid drain,,, have your assistant pump the brakes until tight as possible and then hold the pedal to the floor until the fluid has been bled from the first location. Follow the pedal to the floor as pressure is released and DON'T release the brake pedal until you have made sure the bleeder valve is closed. Repeat this until you have no air at all and clean fluid. Now, do the next wheel. Left Rear! Next the Right Front, and finally the Left Front. By following this method you will have eliminated all of the air from the brake system as long as you don't have any leaks.

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I just replace the brake booster on a 2000 Chevy Malibu. Now the front brakes drag so bad that they are red hot. What do I do to fix this problem? This seems to be an adjustment on the pushrods.

you misadjusted the push rod. It's too long and that's forcing the master cylinder piston past the compensating port. So as the brakes heat up and the brake fluid expands, the expanding fluid can't blow back into the reservoir. So it builds even more pressure in the lines and causes the brakes to apply even harder.
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02skidoo700mxz.No ride in 2yrs. ride 15min, felt drag, brake lever solid as rock, rotor glowin orange. in 10min lever floppy to handle (no pressure). in 30min check lever, now back normal. explain??

taking that this a motor cycle then you have suffered what is known as" brake fade"
to understand the term it works like this
for brakes to work, kinetic energy ( spinning brake rotor) is converted to heat energy by the friction caused by applying the brake
this loss of kinetic energy is the braking action or the bike slowing down
normally there is enough heat transference to the passing wind but if the heat generated exceeds the heat transfer then the brakes and rotor will not absorb any more heat generated by the friction and so the brake stops working
(like oil on the pads or linings)
what cause it to happen--
there is clearance between the disc rotor and the brake pads but if the brakes are applied then the brake fluid is pushed out against the pistons and applies pressure to the rotor ( braking action)
when the brake is released the fluid is returned to the reservoir and there is no problem
BUT
if that fluid is not allowed to return fully, the brakes remain on( your brake drag) and the heat generated besides going to the air , also heats and expands the brake fluid
with nowhere to expand to , the brake is applied by the expanding fluid
AS all brake fluids are hydroscopic( absorb moisture from the atmosphere) the water in the brake fluid boils off and you loose any pressure because the system is now full of air and air compresses
when the brakes cool down the brake action comes back as the air has bled back to the reservoir
The fix is to replace the master cylinder and the brake fluid and to ensure that the calliper slides freely on the mounting rods so that it self centres over the rotor
what you have experienced is very common on heavy trucks on long down grades where the brakes over heat and fade resulting in control of the truck
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1995 Chevy p30 chassis builds pressure and applies brake while moving or setting until you bleed front brakes

pressure build up in brake lines indicates a blocked compensating port in the master cylinder. The heat generated by brake operation is expanding the brake fluid which cannot return to the reservoir and so it is apply the brakes. If you have an ABS system on the vehicle have it checked out by an accredited brake shop for operation as well
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1answer

front brakes drag causing roters to heat up.

You probably have air in the brake system. As you ride the bike, the pads do rub on the rotors ever so slightly. In doing so, they get warm and heat up any air in the brake system. As air is heated, it expands and causes the pads to rub harder creating more heat, which further expands the air. Finally, the pads are pressing against the rotors so hard that they heat up. Bleed the front brake system of all air. Do run the master cylinder dry while bleeding the brake.

To bleed the brake, make sure the master cylinder is full of the correct type of brake fluid. It will tell you the type of fluid to use on the master cylinder top. Now, to bleed brakes the steps must be done it this order. Apply the brakes by squeezing and holding the lever. Open one of the bleeder valves and allow the fluid and any air to bleed out. The lever will go to the handlebars. Close the brake bleeder valve. Release the lever and allow the master cylinder to refill. Check the level in the master cylinder. Now repeat the process on the other brake caliper. You may have to go back and do this a couple of times one each caliper. Just make sure you don't allow the master cylinder to run dry. Now, your front rotors will run a bit warm because the pads do stay in contact with them all the time. This is one advantage of disc brakes, the pads keep the rotors clean and dry all the time meaning you have good brakes all the time with them. The old drum brake would get water in them when riding in the rain and you basically didn't have any brakes until the brake shoes dried the water out.

Good Luck
steve
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