Thursday, May 6, 2010

Bike Builders Tips: Bleeding hydraulic disk brakes - forum

First, make sure all connections are tight and don’t let any air into the system. Also, check the hose for cracks or pinholes. If all is well, then try back flushing.

You'll need one of those pump oil cans and rubber tubing for a few bucks at any auto parts store. It's simple. Fill the can with fluid, and attach the rubber hose to the nozzle. Open the bleeder (not too much, just enough to let fluid pass through) and the fill cap on the handle.

Pump the fluid in through the bleeder until it comes out of the fill hole. Hold the pump down on the can while closing the bleeder. If the system calls for having an air space in the handle, remove the correct amount of fluid.

I've been using this method on cars for the last 35 years. It's a one man operation, and requires inexpensive tools. If you find it easier to climb under the car than remove all the wheels, you can do that too. You'll need four jack stands, unless you have a truck or SUV that has plenty of room to slide under the car.

You'll need four jars or cans to hold the spent fluid, the oil pump can, and some tubing. Any tubing that fits tightly over the bleeders will do; it doesn't have to be clear. 1/4" or 5/16" ID is likely, but there are a few bleeders that will require 3/8". You'll also need a length of wood or metal bar to wedge between the brake pedal and the seat.

Fill the master, and replace the top. Install the tubing on all the bleeders and let them drain into the jars or cans. Open all the bleeders. Push down on the pedal, and wedge the bar in. Check the level of the master. If it's less than 1/2 full, fill it. If not, let up on the pedal and repeat until the master is less than half full. You'll now know how many times to pump the pedal before you have to hold it down. Fill and drain the master three or four times to make sure the dirty fluid is out of the system. The last time, leave it less than 1/2 full.
Close the front bleeders, and the rear one closest to the master. Starting from the furthest wheel from the master, pump fluid through the bleeder.

When the oil can is near empty, close the bleeder and remove the tube. Go to the master, and remove fluid until it's less than half full. A syringe, hydrometer, or turkey baster all work great for this. Repeat for the other rear wheel, then the front on the opposite side of the master, then the final wheel. It sounds like a lot of work, but it's really not bad.

Of course, if you have someone to help, it's a lot easier. Or you could buy a pressure kit for $50-$60, or a pressure nozzle system for about $30. Stay away from the cheap $15 HF kits because they don't last. Also, this system of flushing is not recommended for vehicles with traction control that use the braking system.
And, you may or may not have to do an additional procedure to flush the ABS system. Repair manuals for your vehicle will describe the procedure for ABS flushing and bleeding, and whether it has to be done before or after flushing the main system.

~ The Kid, Atomic Zombie Builders Forum

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