Brake re-assembly problems/questions
01-22-04, 12:02 PM
#1
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Brake re-assembly problems/questions
Last night I finally finished putting everything back on the car. I rebuilt the brake calipers, repacked the bearings, shot the hub cavity full of grease, and put the old rotors and pads back on (it is going to get new pads, but the store gave me the wrong ones and I just wanted to make sure everything was in order). All that work was done on the front side -- I haven't touched the rear yet.
I knew that I'd have to bleed the brakes, since I had phsyically disconnected the calipers so I could clean them up and rebuild them at the kitchen table (cold garages, bad!) So, before I put the rims back on the studs, I topped off the fluid in the master cylinder, opened the bleeder screw on the front, attached a length of tubing, submerged the other end in a full bottle of brake fluid, and depressed the brake pedal.
Before I took anything apart, the brakes were more-or-less okay. They were dragging a bit, but there was plenty of pedal response. Now, however, the pedal is almost totally lacking in response. I get no bubbles, no brake fluid, and no piston movement. As I pump the pedal slowly, I don't feel any of the stiffness that I'd expect from vaccum-assisted brake system when the motor isn't running. I do hear a hissing noise coming from the general direction of the master cylinder. I even tried starting the engine for a while (yes, I let it warm up!
), to see if building up some vaccum would help. Same result, but I did notice that there was a little bit of stiffness in the pedal while the motor was running and for three or four slow pumps after the engine was shut down.
I'm somewhat baffled, but I have a few ideas. I'm hoping that someone can help me pull my head out of my rear... While the car was up on jack stands for the last month-and-a-half, did I develop a vaccum line break in the power assist module? Do I need to bleed the master? Do I need to start in the back and bleed the right rear, left rear, right front, left front, then the master? I've checked for kinks in the line, and there aren't any. I double checked to make sure I removed the plugs I put in the caliper to keep the innards clean, and they've been removed.
I knew that I'd have to bleed the brakes, since I had phsyically disconnected the calipers so I could clean them up and rebuild them at the kitchen table (cold garages, bad!) So, before I put the rims back on the studs, I topped off the fluid in the master cylinder, opened the bleeder screw on the front, attached a length of tubing, submerged the other end in a full bottle of brake fluid, and depressed the brake pedal.
Before I took anything apart, the brakes were more-or-less okay. They were dragging a bit, but there was plenty of pedal response. Now, however, the pedal is almost totally lacking in response. I get no bubbles, no brake fluid, and no piston movement. As I pump the pedal slowly, I don't feel any of the stiffness that I'd expect from vaccum-assisted brake system when the motor isn't running. I do hear a hissing noise coming from the general direction of the master cylinder. I even tried starting the engine for a while (yes, I let it warm up!
), to see if building up some vaccum would help. Same result, but I did notice that there was a little bit of stiffness in the pedal while the motor was running and for three or four slow pumps after the engine was shut down.I'm somewhat baffled, but I have a few ideas. I'm hoping that someone can help me pull my head out of my rear... While the car was up on jack stands for the last month-and-a-half, did I develop a vaccum line break in the power assist module? Do I need to bleed the master? Do I need to start in the back and bleed the right rear, left rear, right front, left front, then the master? I've checked for kinks in the line, and there aren't any. I double checked to make sure I removed the plugs I put in the caliper to keep the innards clean, and they've been removed.
01-22-04, 12:59 PM
#3
Yes, I just did mine and it took a long time to pump out all that air. Also, if you don't close the bleeder valve between pumps, you may be just drawing air back into the caliper through the valve. Pump and hold the peddle to the floor (wives and girl friends are good for this), then open the valve to let all the air out, then close the valve and have your assistant pump it again, open the valve, close the valve, pump, open, close, etc. Also, with all that pumping air, you may have gotten some air in the rear lines, so you may want to bleed these too.
01-22-04, 02:14 PM
#4
84SE-EGI helpy-helperton
Seems like we all took it upon ourselves to rebuild our brake calipers lately! I did mine a few weeks ago and managed to bleed them myself without too much problem.
Understanding the hydraulic system is key to getting all the air out, and performing the bleeding in the correct fashion.
The brake master cylinder grabs fluid from the reservoir and pushes it out through the solid (metal) lines to each corner of the car. At each corner, there is a flexible line (hose, rubber or Stainless braid), that connects the hardline to the caliper. Each caliper has a single piston that is pushed out through hydraulic pressure to compress the pads against the disks (front) and drums (rears, on all but GSL's and SE's). You need to have no air bubbles in the line, all the way, to prevent a 'mushy' brake pedal. Any air will dramatically decrease braking force on all wheels, and can cause serious problems in emergency braking situations.
When you bleed your brakes, the idea is to do it in a way that eliminates any air bubbles from the lines. Most bleeding takes place from the furthest from the master cylinder to the closest, but some do it exactly the opposite - in truth, it doesn't matter much which way, just use a systematic approach.
1) top off the brake master cylinder
2) At the caliper that you're bleeding, attach a clear silicone or PVC hose that goes down into a small cup with a small amount of brake fluid in it (not a NEW bottle, you're going to be throwing this 'used' fluid away...). The clear tubing allows you to see the bubbles get pushed out, and when no more bubbles flow - you're done.
3) Get an 8mm box-end wrench for the bleeder screw, and with someone inside the car, loosen the brake bleeder screw with the hose attached to it. Have them push gently and gradually until the pedal is almost to the floor, and HOLD IT THERE - do not let up on the pedal, or you'll suck air through the bleeder back into the system. Quickly, close the bleeder screw.
4) top off the brake master cylinder (each pump will result in brake fluid being drawn into the lines, replacing the air and old fluid)
5) Once the bleeder screw is closed, have the person allow the brake pedal to return to normal position, slowly and gently. This refills the master cylinder pistons with new fluid and prepares for the next pump.
6) Open the bleeder screw, have assistant push on brake pedal, smoothly and gently, repeating step 3, above. The idea is to keep doing step 3/4/5 until you no longer see air bubbles in the clear line coming off of the bleeder screw. Once you see clear fluid, not dark, it is fully bled, and the hardline, flexible line, and caliper all contain fresh, clean, new fluid.
7) tighten down the bleeder screw to about 15-20 ft/lbs (very light torque), put the rubber cap back on to prevent grease and dirt from getting stuck in there, and move to the next caliper.
8) top off the brake master cylinder.
Doing all of these steps will ensure that you have all air out of the system, and the brakes can operate the way they were designed.
New brake fluid can make a difference - as it gets old, it absorbs water from the air, resulting in a lowered boiling point. This can lead to diluted fluid which results in greater pedal effort, brake fade under hard use, and poor braking performance. HTH,
Understanding the hydraulic system is key to getting all the air out, and performing the bleeding in the correct fashion.
The brake master cylinder grabs fluid from the reservoir and pushes it out through the solid (metal) lines to each corner of the car. At each corner, there is a flexible line (hose, rubber or Stainless braid), that connects the hardline to the caliper. Each caliper has a single piston that is pushed out through hydraulic pressure to compress the pads against the disks (front) and drums (rears, on all but GSL's and SE's). You need to have no air bubbles in the line, all the way, to prevent a 'mushy' brake pedal. Any air will dramatically decrease braking force on all wheels, and can cause serious problems in emergency braking situations.
When you bleed your brakes, the idea is to do it in a way that eliminates any air bubbles from the lines. Most bleeding takes place from the furthest from the master cylinder to the closest, but some do it exactly the opposite - in truth, it doesn't matter much which way, just use a systematic approach.
1) top off the brake master cylinder
2) At the caliper that you're bleeding, attach a clear silicone or PVC hose that goes down into a small cup with a small amount of brake fluid in it (not a NEW bottle, you're going to be throwing this 'used' fluid away...). The clear tubing allows you to see the bubbles get pushed out, and when no more bubbles flow - you're done.
3) Get an 8mm box-end wrench for the bleeder screw, and with someone inside the car, loosen the brake bleeder screw with the hose attached to it. Have them push gently and gradually until the pedal is almost to the floor, and HOLD IT THERE - do not let up on the pedal, or you'll suck air through the bleeder back into the system. Quickly, close the bleeder screw.
4) top off the brake master cylinder (each pump will result in brake fluid being drawn into the lines, replacing the air and old fluid)
5) Once the bleeder screw is closed, have the person allow the brake pedal to return to normal position, slowly and gently. This refills the master cylinder pistons with new fluid and prepares for the next pump.
6) Open the bleeder screw, have assistant push on brake pedal, smoothly and gently, repeating step 3, above. The idea is to keep doing step 3/4/5 until you no longer see air bubbles in the clear line coming off of the bleeder screw. Once you see clear fluid, not dark, it is fully bled, and the hardline, flexible line, and caliper all contain fresh, clean, new fluid.
7) tighten down the bleeder screw to about 15-20 ft/lbs (very light torque), put the rubber cap back on to prevent grease and dirt from getting stuck in there, and move to the next caliper.
8) top off the brake master cylinder.
Doing all of these steps will ensure that you have all air out of the system, and the brakes can operate the way they were designed.
New brake fluid can make a difference - as it gets old, it absorbs water from the air, resulting in a lowered boiling point. This can lead to diluted fluid which results in greater pedal effort, brake fade under hard use, and poor braking performance. HTH,
01-23-04, 04:51 PM
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Just as an update:
I went to Advance Auto Parts and bought a $6.99 One-Man Brake Bleeding Kit. Looked like it had been used and returned. I used it to bleed all four calipers, and everything is right as rain with the brakes.
Thanks for the help!
I went to Advance Auto Parts and bought a $6.99 One-Man Brake Bleeding Kit. Looked like it had been used and returned. I used it to bleed all four calipers, and everything is right as rain with the brakes.
Thanks for the help!
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