Bleading the brakes...

phycobob

Registered User
Just got new cross drilled rotors and kvr pads for the front and rears today. Man, those main bolts are a pain to get off! Broke TWO torx sockets in em! Anyway, I thought I bled the brakes right, but they feel very spongy, actually worse than before the brake job. Is there a special way you have to bleed an ABS system? Only done it on conventional brakes before. Oh, and is it ok if I use DOT 5 brake fluid? Do I compleatly have to flush the old stuff out? Thanks in advance!
 
A failing ABS accumulator shouldn't affect the bleeding of the brakes, just the operation of the brakes :eek: as it provides the power assist. But, if before your brake job you had sonstant firm brakes, you should have some time before you need to panic.

For the front brakes, presuming you know how to bleed the calipers such that no air reenters the caliper, then its just the usual:

setup: loosen bleed valve ever so slightly, reclose finger tight, hook up clear tubing (to see the air bubbles) to the bleed valve and the other end submerged into a tin can with about 3/4" of brake fluid.

1. have assistant (kids are good for this) hold down pedal,
2. open valve enough for fluid to flow out (not too much)
3. bleed for a few seconds
4. close valve
5. release pedal
6. repeat steps 1-5 until you have bled around 1/2 cup and no more air is seen going out of the valve into the tubing. Be sure to refill the reservoir occasionally.

Now the rear brakes are different; with those, you have to turn the key on to the run position (to keep the pump running to charge the accumulator).. and you don't need anyone to press the pedal, although I suppose they could to help.
 
hmmm....still mushy....

Ok, I did it as you said.....went through 2 large bottles of brake fluid....there was a little air at first...but only from the rear passenger brake. Any other reason for the mushyness?
 
Did you do just the fronts????

It could be that your rear pads have some "give to them".

Anyway, I don't think that you can use DOT 5 brake fluid in ABS brakes. I don't know the reason why. I use DOT 4 LMA or Valvolne Syntec.

Also supposedly a DOT 5.1 exists that CAN be used in ABS brakes, but I don't know where to get it. Consider also getting braided steel brake hoses for a firmer pedal.

How mushy is mushy? Are they like 1" mushy, or pedal to the floor mushy?
 
pedal to the floor mushy....

Not totaly to the floor, but it doesnt start braking till its just about all the way depressed, and has a verrrry small gap between soft braking and hard-lockup-your-tires breaking. Oh, and I decided to use DOT 3 instead of the DOT 5 because I didnt hear back from anyone in time....had to go to work ya know! :) Pedal was pushed to the floor as well when I closed the valves clown...oh, and I put too much fluid in at first, cause when my buddie was pumping the brakes, fluid started gushing out the resavour. Its hard as hell to see when the fluid level line is at in that yellowed out SOB. I guess I'll just try again tommorow....
 
If the pedals are that mushy,,,,

You've still got air in the lines/reservior/abs unit somewhere.

It's weird, but stomp your brakes when you are driving slow. The ABS will start shaking the brake pedal, but with each shake, you will feel the pedal "rise" up a bit. Perhaps that might purge some air.

Are you sure you don't have any leaks anywhere?
 
Actually....

Actually, if I stomp my brakes....the orange antilock light comes on, and my brakes lock up. I had to do that once at 80mph before I knew the accumlator was bad, and they locked up, and I nearly wrapped myself around a tree. Also had to get new tires cause it ripped them down to the steel belts. I've tried numorus times, but the antilock system just isnt working.
 
That sounds like half the problem right there..

Consider fixing the abs first and see if you still have a mushy pedal. Usually a bad accumulator means a rock hard pedal with little to no stopping power. Maybe your accumulator's diaphragm is bad but it somehow took on air when you changed your calipers. Now it is trapped up top and there is no way to get it out unless you replace the accumulator.....
 
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