bleeding brakes with vacuum bleeder

3 replies to this topic
  • antfizzle

Posted September 12, 2012 - 10:35 PM


Okay, I have a new brake hose on the front, I see no signs of anything wrong on the caliper, but I have went thru a whole bottle of brake fluid bleeding these front brakes, what gives, im not letting the MC ever run dry, and I am still sucking out bubbles and air in thru the hose, just for kicks, I bled the rear the same way, and as soon as I cracked the bleeder open a full hose full of brake fluid came out, no bubbles what so ever, thanks guys, these front brakes have me pulling my hair out. ...... - Anthony

  • marv02

Posted September 13, 2012 - 05:35 AM


Back flush the brakes with a syringe and a rubber hose.

Put the rubber hose on the syringe put the hose into a botttle of brake fuild fill the syringe dont let any drain out put the open end of the rubber hose on the brake bleeder on the brake caliber with the master cylinder cap off open the bleeder up and push the fuild up into the master cylinder.

Yes it can cause a mess but air wants to go to the highest point not down low to the brake caliber.

Edited by marv02, September 13, 2012 - 05:38 AM.

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Posted September 13, 2012 - 06:16 AM


Back bleeding is a good way of doing it

At the moment air is trapped in the bend of the brake line or at the master cylinder

When you back bleed make sure the syringe seals well onto the caliper , otherwise You can feed air into the system .

  • grayracer513

Posted September 13, 2012 - 08:12 AM


You don't need any of the trick equipment to bleed the brakes, especially the front. Fill the master cylinder, leaving the cover off, and open the bleeder screw. Watch the level in the reservoir. If it does not begin to drop with the screw open, it's because it's air locked; there's a bubble in the way. You can sometimes dislodge it by pushing the caliper piston back, but it isn't necessary.

Close the bleeder, then pull the lever only enough to move the piston the first 3mm or so. This should cause a bubble to emerge from the fill port at the bottom of the cylinder. Continue doing this several times and then try opening the bleeder again.

What you are trying to arrive at is a condition where the fluid flows down the line and out the bleeder on its own because of gravity. Once this starts, let it just continue to flow, adding fluid as needed to keep the reservoir from running dry. When you stop seeing bubbles at the bleeder, close it.

At this point, turn the bars so that the master cylinder is tipped hose end down a bit and "tickle" the lever that same 2-3mm a couple of times to release the bubble that wants to get stuck in the bore. If you pushed the pads back, pump them back out against the rotor, add fluid and check the feel. You should be good. If it still feels a little mushy, put a light pressure on the lever and loosen the hose fitting at the master. Don't release the lever until you tighten the fitting again.

A second very effective method that requires nothing expensive is to build a simple gravity back-flush bleeder. Connect a funnel to the bleeder screw with a length of hose long enough to allow the funnel to be hung at a height above the master cylinder. Remove the line at the caliper and dismount the caliper. Open the bleeder screw and fill the funnel while holding the caliper so that the hoe fitting and not the bleeder is at the high point until the caliper fills completely, then reattach the hose and mount the caliper.

Continue filling the caliper via the funnel and hose until fluid free of air rises from the master cylinder. Again, tickling the lever will help dislodge air at the top.

Air at the master cylinder hose fitting is the most common cause of failures of bleeding brakes. Fluid simply flows around and/or under the bubble without moving it. This is even more a problem with rear brakes because the fitting is the system high point. If the last thing you do is always to crack and bleed that fitting, you'll have a lot better luck. :thumbsup:

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