Ok everyone, here U go, Brake Bleed 101! Just b/c someone asked, and I had to type this all out finally. This is the program that weve used in the shop for almost 30 yrs. now, and have always sent our brake jobs out w/The best brake pedal that any of our customers ever had, every time... So, here U go. I will post this again later in my Albums once I generate some pics and diagrams to go along w/this text of the procedure. 1st, make sure that Uve got adequate brake pedal free play, this is the clearance between the master cylinders piston at its rest position and the push rod from the pedal assy. that pushes it. If there is no brake pedal free play, then the master cylinder pistons may not return fully enough to expose the fluid fill ports to the line/s coming from the master cylinders fluid reservior, and that are drilled into the master cylinders piston bores just b4 the point that the pistons stop at rest. If those ports are not re-exposed when the pistons are returned to their at rest position due to a lack of pedal free play, then the system will not be able to draw up the fluid from its reservior each time after the pedal has been returned to its rest position. This will not only screw up any hope for a successful brake system bleed, but also not allow the brake shoes to fully return each time theyre actuated b/c those supply ports also allow any excess system fluid pressure to return the fluid back into the reservior as well, and will result in a rock solid pedal and locked up brakes after just a few pedal strokes. Make sure all of the brake shoes are adjusted up fully b4 trying to bleed the brakes, otherwise U will merely be exercising the brake shoe return springs, and never attain a good brake system bleed. The purpose of bleeding the brake hydraulic system is to purge all of the air out of it, b/c gasses are compressible, and fluids are not. As long as theres any air anywhere in the brakes hydraulic system, U will not be able to attain a nice high and solid brake pedal position. To adjust the brake shoes in the front of the std. Beetle, since the shoes are oriented top and bottom, U must adjust the top brake shoe fully w/a moderate amount of drag first, then the bottom one, b/c if the car is jacked up w/the wheel in the air for brake adjustment, if U adjust the bottom shoe first the brakes can be locked up when U set the car down, b/c of the way that the axial play in the front wheel bearing sets comes out of them under the load of the cars weight, vs the way they are w/o the cars weight on them when the cars wheels are raised off of the ground for the purposes of bleeding and adjusting the brakes. When adjusting the brake shoes, adjust the top shoe up until moderate drag is obtained, then b/c they are also not floating assys., they are also not self centering, so after Uve adjusted each shoe up for moderate drag, then tap solidly on the backing plate. This centers the brake shoe in the drum, and then readjust that brake shoe again until moderate drag is attained again, and repeat the process again until there becomes no difference in the amount of drag of the brake shoe after the backing plate has been vibrated/tapped w/the hammer. Only after all of the shoes have been properly adjusted will U be able to follow through w/the bleeding of the air from the brake lines. Using this method weve never had to bench bleed the masters, and have always just put em in. Once Uve got all of the brake shoes fully adjusted, Ure ready to bleed the hydraulic system. Get Urself an old clear plastic water bottle, or pop bottle, and cut a hole in the lid of it that U can pass a piece of hose through that holds the hose snugly. First select a piece of hose that fits the bleeder valve of wheel cylinders snugly first b4 making the hole in Ur bottle cap for it, so that U can make it tight. This is important b/c if the bottle gets tipped over accidently, then it wont spill any of the brake fluid that accumulates in it during the bleeding process. Next, pour about an inch or so of brake fluid into the bottle so that the end of the hose going through the cap of it is completely submerged into the brake fluid in the bottom of the bottle. This insures that no air will be drawn back up Ur Bleeder Hose, and back into the brakes hydraulic system. Its good practice to start Ur bleed w/the wheel cylinder furthest away from the master cylinder, in the case of the Beetle that would be the right rear, or passenger side rear wheel cylinder. First put the box end of the wrench U are going to use to open and close the bleeder valve onto the bleeder in a position that affords U enough swing room to open and close the bleeder valve, then slip the end of U bleeder hose thats coming out of Ur Bleeder Bottle onto the bleeder valve of the wheel cylinder that Ur going to bleed. Then just crack the bleeder valve open, and begin pushing the brake pedal repititiously, generally about 4 or 5 pumps, waiting for a short time each time after U let the pedal return to its rest position so that it can draw up more fluid from the master cylinders fluid reservior to replace the fluid that was just displaced from the system into Ur bleeder bottle on the cracked open bleeder valve. Do this until no more air bubbles can be seen coming from the end of Ur bleeder hose that is submerged in the accumulating fluid in Ur brake bleeder bottle, then close the bleeder valve, and move to the next furthest brake assembly from the master, and repeat that process, until U have bled all of the air out of the system at all 4 brake assys. If the brake pedal still feels soft and mushy instead of hard and firm when its depressed and the brakes are actuated, that would indicate that theres still some air left in the hydraulic system that needs to be bled out, and it may be necessary to repeat the bleeding process again. This could also be an indication that theres a misalignment of the brake shoes to their drums due to bent or warped brake backing plates going on somewhere in the system. To check for this watch for any movement between the backing plates and the brake drums as the brakes are being fully actuated. That has also been a problem that I have found sometimes through the years. Make sure to check and fill the brake systems brake fluid reservior often during the bleeding process, b/c that is where the system replenishes the fluid from that U are bleeding out of it. U will use up the brake fluid from the systems reservior rapidly during the bleeding process. If U run out of fluid in it, then the system will draw air into itself again, and U would have to begin the process all over again. Then, to get that rock hard, super high brake pedal that we all love so much, it may also be necessary to do a final adjustment of all of the brake shoes as well after the bleeding process is completed, and after the shoes have been exercised by their actuation via their hydraulic system. This sometimes reposition the shoes to their drums even better than what the jarring impact of a hammer blow to the backing plate can. Happy bleeding and adjusting everyone! :)
Posted on: Sun, 27 Oct 2013 16:56:46 +0000
Trending Topics
Recently Viewed Topics
© 2015