Spongy Brakes
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Join Date: Nov 2008
Location: Burlington, Ontario, Canada
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I have an ABS problem that I have not yet had time to investigate, but as a bonus my brake pedal now feels nice and firm.
Is this a normal characteristic of ABS or do I have air in my ABS unit. If so, how do I bleed it out?
I have replaced the rear calipers this year and used my pressure bleeder to flush the system and made sure that the fluid level never went low so I do not believe that I drew air into the system.
The pedal does not go down far but always felt a little spongy with normal ABS.
Brian
Is this a normal characteristic of ABS or do I have air in my ABS unit. If so, how do I bleed it out?
I have replaced the rear calipers this year and used my pressure bleeder to flush the system and made sure that the fluid level never went low so I do not believe that I drew air into the system.
The pedal does not go down far but always felt a little spongy with normal ABS.
Brian
#2
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You will not feel the ABS unless you are in a full lock down of pedal. If you stop on gravel you can sometimes feel the ABS work. If you changed rear pads did you also bleed fronts? I would rebleed entire system to flush any dirt that might be in it and retest pedal. Brakes should be firm on startup with a slight dip in pedal after start. If still spongy check rubber hydraulic lines on front and rear. After a couple of years moisture in the system can make the brakes spongy.
#3
#4
Join Date: Nov 2008
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I should have made myself clearer.
Under non ABS braking (moderate) the pedal feel is much more solid than when the ABS was operational. Even when parked with the engine running there is a noticeable difference.
Yes, I did bleed the whole system and flushed out the old fluid with new of a different colour so I could be sure that the old fluid was completely replaced.
I would expect softness in any flexible line to feel the same with or without ABS since the lines are common to both systems.
My question remains - has anyone noticed a difference in pedal movement and feel when ABS is present or not??
Brian
Under non ABS braking (moderate) the pedal feel is much more solid than when the ABS was operational. Even when parked with the engine running there is a noticeable difference.
Yes, I did bleed the whole system and flushed out the old fluid with new of a different colour so I could be sure that the old fluid was completely replaced.
I would expect softness in any flexible line to feel the same with or without ABS since the lines are common to both systems.
My question remains - has anyone noticed a difference in pedal movement and feel when ABS is present or not??
Brian
#5
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The usual reason for the brakes firming up is a problem with the servo. To test it, with the engine stopped, pump the brake pedal about 10 or 12 times to fully use up the vacuum in the servo system. Then the pedal should feel really firm. Keep it pressed down and start the engine. The brake pedal should sink down as the vacuum is pulled if the servo is good. If not, first check the vacuum line to the servo for leaks or the non return valve in that line not working. After that it's looking like a servo problem.
#6
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When you say non-ABS brakes, does this mean you have removed all fuses and relays to the ABS system? The reason I ask, ABS is only in use on full hard pedal ( as 2 feet on pedal ) braking. Otherwise the car will brake as a regular car. So, are you hard braking when problem exists, or are you doing stop at intersection from interstate 60 - 0 MPH stopping. As ABS is a pulsating brake ( with lots of noise ) and no squeal on stop but lots of chirping. Usually any modulation or sloppy pedal can be from loss of vacuum to booster. Usually ABS problems go unnoticed until brake pads wear out in a few miles from new.
#7
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Right now Im like that feeling you get back in school when you know the answer and you want to answer it so bad. It took me a while to figure this one out.
Bleed it again with your pressure bleeder, but hold the bottle higher than the caliper. it sounds weird but give me a chance![Big Grin](https://www.jaguarforums.com/forum/images/smilies/biggrin.gif)
best brake fluid for this car:
Motul Brake Fluid DOT 5.1_
Bleed it again with your pressure bleeder, but hold the bottle higher than the caliper. it sounds weird but give me a chance
![Big Grin](https://www.jaguarforums.com/forum/images/smilies/biggrin.gif)
best brake fluid for this car:
Motul Brake Fluid DOT 5.1_
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