How to best insert new break fluid and bleed the line
I am learning to service my bike and am now tackling putting brake fluid in and bleeding the brake line. I have a specialized, enduro mountain bike. Any tips on how to proceed would be appreciated, thanks.
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Re: how to best insert new break fluid and bleed the line
Depending on which brand of brakes you have on your bike, you will need a brake bleeding kit specific to those brakes. Some of the fittings in the kit are such that you can't make them or obtain them elsewhere easily. There are various fluids used also. Some brakes use mineral oil and some brake fluid vary in density from DOT 3 to 5.1. This is something that is more easily done with a helper and the right tools. A good bicycle shop can do this at a nominal fee or they can sell or order you what you will need.
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The proportioning valve has blocked off your rears brakes from getting fluid. My suggestion is to by a syringe 50cc 2oz size fill with brake fluid and force fluid backwards to master cylinder this should center the valve and remove the air.
Bleeding the brake is not difficult but it must be done in a certain way. Follow these directions exactly. First remove the top from the rear brake master cylinder and check the fluid level. If you add fluid during this process, make sure you are putting the right kind of fluid in the reservoir. It should be printed right on the top cover of the reservoir. Place the top back on the reservoir but you don't have to put the screws in it. All we are going to do with it at this point is keep brake fluid from splashing on your bike. To bleed the brakes, depress and hold the rear brake pedal. Open the bleed valve on the rear brake about a half turn and allow the brake fluid and air to bleed out. Close the brake bleeder valve. Release the brake pedal and check the fluid level in the reservoir. Do not allow the reservoir to run dry. Continue to bleed the brakes until you have a full firm brake pedal. Then top off the reservoir and replace the cap and screws. You can put a piece of small diameter clear hose on the end of the bleeder valves to direct the brake fluid into a catch jar and it makes this job much neater. Do not allow the brake fluid to get on painted surfaces as it can damage the paint.
Have you checked your Master Cylinder to ensure that it's full of fluid? If it is empty the best way to bleed the brakes in that case would be to add fluid and then break the caliper bleeders loose and let gravity do its thing. Gravity bleeding is the best way to make sure you don't trap air in the brake system. Make sure you keep the master cylinder full of fluid while gravity bleeding. Run approx 2 reservoirs full to make sure that you have no more air in the line! And you should be done. Also, the vehicle does not need to be running to gravity bleed. Good luck!
sounds like there is still air in system, put a hose from brake bleeder into jar of brake fluid to bleed and repeat for each set of brakes, checking brake fluid resevoir often. this will remove any air and keeps the line from sucking up air. there are one man break bleeding kits sold at auto parts stores but a clear air hose will work.
Unless you are familiar with bleeding the break system I would not recommend this task. Sometimes it can be very difficult to get all the air out of the system especially if you do not bench bleed the Master. But If you'd like to try you have to break loose the brake lines that connect to the master and remove them. Then you have to remove the two nuts holding it to the brake booster which is usually black and round. When you remove it make sure you have taken out the old seal and you put back the new one. Now before you install the master you should fill it with fluid and push the shaft until fluid comes out the brake line holes. Once this has happened put something to plug it from leaking and install it on the car WITH NEW GASKET. Now install everything in the opposite order and bleed the brakes when your through... bleeding the master just helps you get less air in the system so its easier to do the initial bleed. SO EVEN THOUGH YOU BLEED THE MASTER YOU STILL NEED TO BLEED THE BRAKES FROM EACH WHEEL.
the bleeder valve is the end of the line for break fluid.....you only open the valve when you're bleeding air from the break lines...after that it needs to be shut closed....fluid is leaking out of the bleeder valve because either the valve is not seated correctly or it got grinded down to a point where there is now an opening in it where it does not hold back the fluid....solution is to change the valve...they're only a couple dollars and you can do it your self....it just unscrews off and the new one screws back on...but be ready for a lot of fluid coming out when your replacing it and have new fluid on hand to replace what you lose.
And you'll have to bleed the system again
First of all. Thank you for your service our country appreciates your dedication and your families support.
Bleeding the system is a series of points from front right to back left. then To front left and back right.
then repeat. 2x. After that bleed brake system at the front then the back. over and over. NO disruption of a steady stream, this is a totally sealed system. 0 air. that means if its not perfect its wrong.
The factory actually primes the lines with vacume from the caliper end. keep that in mind.
**Buy a nice new measuring cup and reuse all Fluid.
Dot4 is not cheap.
Please check caliper seals for the "wet" look around the boot and brake line inputs.
This should work. its not uncommon
The only other thing is the Brake reseviour could be sucking in air. Check for capt tightness. Gromet seal. and and the inner plunger not to be stuck in the down position. pluger is a diaphram. not an actual pin...
amazing ride man.. last of the best Wear a helmet plz.
Pump the lever 5 or 6 times w/ bleeder closed
while holding lever, open bleeder
close bleeder, pump the lever.
Repeat as necessary - works best w/ 2 people.
If you really want to get the fluid flowing fast, Loosen the banjo bolt instead of the bleeder the first couple of times. Have lotsa rags on hand..