Recently, I bled the brake system at all four tires until clear fluid pumped out. I bled the car because pedal was firm at halfway point when the car was turned off. After the bleed the firmness of brake pedal didn't improve. Car is a '95 Saturn SL2. Could this be the master cylinder or do you think I should try bleeding the car again?
brake pedal still not firm after complete bleed
- Thread starter mjo
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Got ABS? if so you have to use a scan tool to cycle the pumps while bleeding
I have ABS on a Buick,I have bled my brakes more than once,no scan tool required.
The best way to bleed the brakes on a front wheel drive is to bleed the side closest to the master cylinder first,starting at the front.
After doing this,bleed the front on the opposite side first,then bleed the back,be sure that the back one is the farthest from the master cylinder.This will better get out any air that is trapped in the system.Also,make sure the car is running while doing this procedure.
Hope this helps.
******Also,make sure that you check the master cyl fluid after each bleed,add fluid if needed.******
The best way to bleed the brakes on a front wheel drive is to bleed the side closest to the master cylinder first,starting at the front.
After doing this,bleed the front on the opposite side first,then bleed the back,be sure that the back one is the farthest from the master cylinder.This will better get out any air that is trapped in the system.Also,make sure the car is running while doing this procedure.
Hope this helps.
******Also,make sure that you check the master cyl fluid after each bleed,add fluid if needed.******
Something else,have you checked the rear brake pads? If the rear pads are worn/need changing,the brake pedal will more than likely travel farther before building good pressure.
Also,look at the backs of the rear wheels for wetness on or around the back of the wheel hub and wheel/tire,a wheel cylinder could be leaking causing a pressure drop.
Also,look at the backs of the rear wheels for wetness on or around the back of the wheel hub and wheel/tire,a wheel cylinder could be leaking causing a pressure drop.
wont fix it if an air bubble travelled into the abs unit. the cylinders of the pumps are larger than the outlet passage, so an air bubble can remain in there, despite all the pumping done. When you use the scan tool (the factory required procedure on most save older ford RABS) you force the fluid in the 'cylinder' out (and any air) to where it can now travel down the line. At this point simply opening a bleed screw into a container with tubing and taking the cover off the master will let the brakes bleed by gravity.quote:
Originally posted by motorguy222:
I have ABS on a Buick,I have bled my brakes more than once,no scan tool required.
The best way to bleed the brakes on a front wheel drive is to bleed the side closest to the master cylinder first,starting at the front.
After doing this,bleed the front on the opposite side first,then bleed the back,be sure that the back one is the farthest from the master cylinder.This will better get out any air that is trapped in the system.Also,make sure the car is running while doing this procedure.
Hope this helps.
******Also,make sure that you check the master cyl fluid after each bleed,add fluid if needed.******
now how do air bubbles get into the units?
well,
- let the fluid level fall in the master such that the (usually front) valve picks up air.
- replace calipers/wheel cylinders/lines and when the fluid comes out, air bubbles travel back upward to the master
- over heat the brake fluid such that it boils and decomposes into gasses
point being, if the pedal is spongy and its not the seals on the masters shaft, then you have air int it. bleeding capilers/cylinders/lines are monkey tasks. therefore if the subject vehicle has an ABS unit (kelsey hayes are the worst to bleed) you MUST look at it and you MUST use the correct procedure, not voodoo, folklore or shadetree procedures.
btw - all previous procedures insist you bleed brakes from the longest path FIRST downto the shortest, not the other way around.
The rear wheels were bled first beginning with the left side. It does have an ABS unit on the brake master cylinder. Also the brake booster is fed by manifold vacuum. Would air in an ABS unit cause the pedal to be mushy when the car is off? When I checked recently, the pedal has the same amount of firmness when the car is both turned on and not running. Thanks for the info, everyone.
I had my procedure backwards,my bad,the 2 AM thinking and little sleep will play games on your mind.
Instead of listening to the board,go and buy a Chiltons or a Haynes manual at a parts house and follow the advice in it.
I have some manuals,the manual I have that covers ABS gives a bleeding procedure,however,it doesn't specifically name your car.Since it doesn't specifically name your car type,the procedure my manual lists may or may not be completely correct for your car.
Also, THERE is a bleeding procedure that DOES call for bleeding the farthest from the master cylinder LAST .I can quote it from the manual if SOME would like for me to.
"Brake pedal still not firm after complete bleed."
Does anyone know if Viagra can be added to an automotive brake system?
Does anyone know if Viagra can be added to an automotive brake system?
With the car running, and the vacuum boost applied, the pedal may feel mushier than with the system with no vacuum boost [brakes pumped with the engine off, numerous times].
Is you problem a soft pedal or just a low one? If the rear brakes are out of adjustment, all the bleeding in the world will not raise the pedal. Sometimes a hardware problem in the front can cause the piston to retract giving a low pedal. Does the pedal go down with little resistance and then stop suddenly? Then quickly return to little resistance when you let off? That is excess travel. With air in the line, the resistance builds as the pedal goes down, and then it wants to spring back.
I find the Chiltons inadequate, and the Haynes not much better. For the same price, you can have a used real shop manual, see www.factorymanuals.com or Ebay.
[ September 02, 2004, 08:41 AM: Message edited by: labman ]
I find the Chiltons inadequate, and the Haynes not much better. For the same price, you can have a used real shop manual, see www.factorymanuals.com or Ebay.
[ September 02, 2004, 08:41 AM: Message edited by: labman ]
Two other things you should look into:
Check your brake pads, and make sure that they have uniform wear on them. Last month, I had the same problem you had, and it turned out that one of my rotors was heavily pitted (from winter road salt) which caused the leading edge of my break pad to get much more wear than the trailing edge. The end result: a wedge-shaped break pad. The other three pads in the front were fine. I replaced the pads, and the excess travel went away.
Another, less likely problem: If the backing plates on your break pads are not fitted properly, broken, or loose, they will put pressure on your pad after you release, causing the gap at this pad to become excessive over time. When you check your break pads, make sure that these plates are in good shape.
Check your brake pads, and make sure that they have uniform wear on them. Last month, I had the same problem you had, and it turned out that one of my rotors was heavily pitted (from winter road salt) which caused the leading edge of my break pad to get much more wear than the trailing edge. The end result: a wedge-shaped break pad. The other three pads in the front were fine. I replaced the pads, and the excess travel went away.
Another, less likely problem: If the backing plates on your break pads are not fitted properly, broken, or loose, they will put pressure on your pad after you release, causing the gap at this pad to become excessive over time. When you check your break pads, make sure that these plates are in good shape.
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