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  #1  
Old 03-11-2005, 02:34 PM
"99 SL500
 
Join Date: Oct 2004
Location: Jacksonville Fla.
Posts: 332
mushy brake pedal

Hello
I've recently replace pads front and rear with OEM on my 99 SL 500,using the pry and open bleed screw to move the pistons and close while is almost all they way in thus preventing air from entering the caliper and avoid sending fluid back to the line,It has worked fine before in diferent vehicles,but after a few hundred miles of city driving my pedal feels spongy,it doesn't feel firm like before during normal slow down and stop braking,the brakes will stop the car fine but the pedal is not as firm as before.Does anybody knows what I did wrong? I'm quick about blaming myself so let me have it.
Thanks

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  #2  
Old 03-11-2005, 03:42 PM
Speed Junkie
 
Join Date: Jan 2005
Location: Southern California
Posts: 82
air in system... almost certainly

You probably somehow inadvertently let air in there. Normally when using the piston compressors you do not open the bleed screws, as there is no reason to. The excess fluid behind the pistons is simply pushed back into the fluid reservior without issue (might be a good idea to pop the top on the reservoir while compressing the pistons, but don't leave it off longer than that). If there was any vacuum in the system it would have drawn air in through those screws.

Also, unless you are doing a fluid flush/change you should never add brake fluid to the reservior. Otherwise when you use the piston compressor without sucking out the excess fluid, you'll make a huge paint eating mess.

I suggest a full bleed procedure per the factory manual, as you may now have air in the ABS unit as well. If it were my car, I would at this point consider it unsafe to drive, unless carefully and slowly, giving plenty of space for a stop.

If you can't do the bleed, have a dealer do it for you. It's much cheaper than replacing your even your front bumper, and if you run into someone that's the least you'd be changing. I know the front bumper on my SL is $1400 new... WHOLESALE.

One other explanation is that your pads are green faded. When you change brake pads there is a specific procedure for breaking them in (called bedding in the pads). If that procedure is ignored, a film can build up on the pads and rotors reducing their stop effectiveness. I don't think that's the problem in your case, since you mentioned opening the bleed screws.

You might as well have them change out your fluid too while you've got it there/you're at it... throw some motul RB600 or high temp ATE fluid, if you do that, your brakes will practically be on fire before you get a soft pedal from a boiling fluid condition. =)

Just my 2 cents.

Justin

Last edited by Justin_Luhrs; 03-11-2005 at 03:54 PM.
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  #3  
Old 03-15-2005, 03:58 PM
"99 SL500
 
Join Date: Oct 2004
Location: Jacksonville Fla.
Posts: 332
mush

Thank you Justin ,the car just turn 53,000 miles and I see the records stating that the brakes were service at 9,000 and again at 31,000 does not specify fluid change or pads or rotors. I will follow your advise to be sure and have the fluid change,a piece of mind is worth a lot.
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  #4  
Old 03-16-2005, 01:12 AM
Ara T.'s Avatar
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Join Date: Sep 2004
Location: Santa Rosa, CA
Posts: 2,075
It is amazing how much of a difference a bleed will do for you Carlos... especially going downhill... i used to have to stand on my brakes, and even then it was hard to stop.
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Old 03-16-2005, 01:26 AM
Strife's Avatar
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Join Date: Apr 2004
Location: KY USA
Posts: 2,238
Quote:
Originally Posted by Justin_Luhrs
You might as well have them change out your fluid too while you've got it there/you're at it... throw some motul RB600 or high temp ATE fluid, if you do that, your brakes will practically be on fire before you get a soft pedal from a boiling fluid condition. =)
Justin
I would definitely change the brake fluid at this opportunity. I had to replace 4 calipers eaten by water in the fluid. Also,I've read some articles about how hygroscopic brake fluid is and it's frightening. In a perfectly sealed system (no one's is) you can get 3%/year water. Now multiply that by # of years. The boiling point of the fluid drops very, very quickly with increasing water percentages.

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