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Simple question about changing brake pads..
12-06-2011, 07:27 PM
#1
Simple question about changing brake pads.. After I remove the caliper and get my new pads on, I know I can take a small clamp and pull the pistons back in place to slide over the new pads. But, if I do this, will it mess up my ABS? Pushing the fluid back through a one way system seems to me like it could mess it up but I have read about people doing this and just taking some fluid out of the resivour before hand..
How does everyone else do it??
How does everyone else do it??
12-06-2011, 07:39 PM
#2
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It will be fine. Take the cap off the reservoir and put a rag around/under it in case some fluid comes out. I have never had fluid come out on any of the vehicles I have done, but taking the cap off will make it easier to compress the pistons. Just take your time and don't crank the clamp as fast as you can, and you will be fine.
12-06-2011, 08:58 PM
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ive been woring on cars for 14 years and never once screwed up a abs system from doin it. how the heck are you supposed to compress them for the fresh pads if not this way
12-06-2011, 11:21 PM
#7
Like everyone else, I also just remove the Reservoir Cap and compress the Piston(s) with a Clamp or Brake Compression Tool. But to answer your question, you could remove the Brake Line from the Caliper or crack the Bleeder and then compress the Piston(s). You would most definitely want to bleed your brakes after using this method, but this would ensure no fluid is being forced backward though the one-way system.
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12-07-2011, 12:05 AM
#8
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Like many, I've done this on ABS cars before without issues. Nothing to worry about, IMO.
12-07-2011, 03:31 PM
#9
And also, I'm assuming the little thing that looks like a horseshoe behind the rotor is the emergency brake?? When putting the new rotor back on, just hang the "horseshoe" back on the little plate?? Any way that is correct to re-install it?
12-07-2011, 04:02 PM
#10
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Like everyone else, I also just remove the Reservoir Cap and compress the Piston(s) with a Clamp or Brake Compression Tool. But to answer your question, you could remove the Brake Line from the Caliper or crack the Bleeder and then compress the Piston(s). You would most definitely want to bleed your brakes after using this method, but this would ensure no fluid is being forced backward though the one-way system.
12-08-2011, 12:09 PM
#13
You can't mess up the ABS by compressing the piston. It has to be compressed or else the new pads would never fit.
As above there are two ways to do it. The simplest is to just uncap the reservoir and then compress on the old pad with a clamp. None should spill unless for some reason you had overfilled it before.
Alternatively, you can open the bleeder when you compress it. The idea being that the fluid that has been in the caliper should be bled out instead of pushed back into the system. Since the system will gravity bleed when you loosen the bleeder, I don't know how you could manage to pull air into it compressing the piston.
As above there are two ways to do it. The simplest is to just uncap the reservoir and then compress on the old pad with a clamp. None should spill unless for some reason you had overfilled it before.
Alternatively, you can open the bleeder when you compress it. The idea being that the fluid that has been in the caliper should be bled out instead of pushed back into the system. Since the system will gravity bleed when you loosen the bleeder, I don't know how you could manage to pull air into it compressing the piston.
12-08-2011, 06:34 PM
#14
I've always compressed the piston, and never had an issue. If you crack the bleeder, you take a chance of introducing air into the system, why even take the chance? By the way, the GM manual also says NOT to disconnect the brake line from the caliper when doing pads.
12-08-2011, 06:38 PM
#15
I usually leave the caliper on, pop the reservoir lid and use a flat head to pry it back using the caliper perch as a leverage point... it literally displaces like 1/2 and oz of fluid (unless you run your **** till the pads are metal to metal)... as long as you push the piston back evenly, it wont hurt a thing...
12-08-2011, 08:55 PM
#16
I usually leave the caliper on, pop the reservoir lid and use a flat head to pry it back using the caliper perch as a leverage point... it literally displaces like 1/2 and oz of fluid (unless you run your **** till the pads are metal to metal)... as long as you push the piston back evenly, it wont hurt a thing...
12-09-2011, 12:09 AM
#17
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The abs is actually a 2 way system. In normal braking fluid is pushed by the master cylinder (about 1200 psi) through the lines to the abs box then through the lines to the calipers. When you release the brake pedal, the 1200 psi bleeds back through the lines going through both the abs sensor and the master cylinder. If the pressure did not bleed off then the brakes would be constantly engaged which can happen if you have a pinched line
With hard braking (brake lock-up) or low traction (snow or ice) When the wheels lock up the abs box acts a hydraulic pump. The pressure hold solenoid valve in the abs box closes and the pressure release solenoid valve opens routing the fluid to the ABS pump which then sends it back to the master cylinder this is what causes the brake pedal to push back against your foot.
So with all of this, using a c-clamp or a piston tool to push the piston back will NOT hurt the abs system. 71novaguy: The abs issue on your dad's Silverado should be a result of changing pads. It could be a bad abs sensor that may have gone out at the same time as the brake change; it is more than likely a coincidence.
Cracking the bleeder to do a pad change only causes more work due to the fact that you now have to bleed the brakes. If done improperly can cause harm to the abs if the master cylinder goes dry and air gets into the abs box, at that point in time to get the system working right the whole brake system needs to be bleed, pain in the ***.
With hard braking (brake lock-up) or low traction (snow or ice) When the wheels lock up the abs box acts a hydraulic pump. The pressure hold solenoid valve in the abs box closes and the pressure release solenoid valve opens routing the fluid to the ABS pump which then sends it back to the master cylinder this is what causes the brake pedal to push back against your foot.
So with all of this, using a c-clamp or a piston tool to push the piston back will NOT hurt the abs system. 71novaguy: The abs issue on your dad's Silverado should be a result of changing pads. It could be a bad abs sensor that may have gone out at the same time as the brake change; it is more than likely a coincidence.
Cracking the bleeder to do a pad change only causes more work due to the fact that you now have to bleed the brakes. If done improperly can cause harm to the abs if the master cylinder goes dry and air gets into the abs box, at that point in time to get the system working right the whole brake system needs to be bleed, pain in the ***.
12-09-2011, 02:19 PM
#18
So if you crack the bleeders you get air in the caliper? That's interesting since the system will gravity bleed when you do that.
If you are really concerned you can put clear tubing on the bleeder and open it as you are compressing the piston and close it right before you bottom it out. Even if you didn't close it before you bottomed it out you would have a column of fluid on top of the bleeder and there would be absolutely no way that air would get in.
Most of anyone who has gotten air in their system has probably done something bone-headed like unscrew the bleeder all the way, take the line off the caliper, or let the reservoir go dry while bleeding.
If you are really concerned you can put clear tubing on the bleeder and open it as you are compressing the piston and close it right before you bottom it out. Even if you didn't close it before you bottomed it out you would have a column of fluid on top of the bleeder and there would be absolutely no way that air would get in.
Most of anyone who has gotten air in their system has probably done something bone-headed like unscrew the bleeder all the way, take the line off the caliper, or let the reservoir go dry while bleeding.
12-09-2011, 03:01 PM
#19
So if you crack the bleeders you get air in the caliper? That's interesting since the system will gravity bleed when you do that.
If you are really concerned you can put clear tubing on the bleeder and open it as you are compressing the piston and close it right before you bottom it out. Even if you didn't close it before you bottomed it out you would have a column of fluid on top of the bleeder and there would be absolutely no way that air would get in.
Most of anyone who has gotten air in their system has probably done something bone-headed like unscrew the bleeder all the way, take the line off the caliper, or let the reservoir go dry while bleeding.
If you are really concerned you can put clear tubing on the bleeder and open it as you are compressing the piston and close it right before you bottom it out. Even if you didn't close it before you bottomed it out you would have a column of fluid on top of the bleeder and there would be absolutely no way that air would get in.
Most of anyone who has gotten air in their system has probably done something bone-headed like unscrew the bleeder all the way, take the line off the caliper, or let the reservoir go dry while bleeding.
12-10-2011, 04:27 PM
#20
Don't open the bleeder valve to depress the piston! 
Brake fluid moves in the lines, both directions, during normal operation. IT IS NOT A ONE WAY SYSTEM. Press the pedal, the fluid moves down from the master cylinder towards the pistons. Release the pedal, and the master cylinder pulls the fluid back up the lines.
Brake fluid moves in the lines, both directions, during normal operation. IT IS NOT A ONE WAY SYSTEM. Press the pedal, the fluid moves down from the master cylinder towards the pistons. Release the pedal, and the master cylinder pulls the fluid back up the lines.