My neighbor's 1999 1/2 ton Suburban has a serious braking problem. The pedal is mushy and it takes forever to stop. The pads are new and I helped him bleed the lines. I was thinking maybe there is a problem with the ABS, or the master cylinder. Any thoughts? I've never worked on an ABS. Is there a way to disable the ABS and see if things improve?
CK5
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1999 Suburban brakes
- Thread starter Dallin
- Start date
Mushy pedal sounds like a bad master cylinder. When the ABS kicks in, you will hear the motor running and feel a slight vibration in the brake pedal.
Bleeding the lines on my '99 Tahoe was a PITA. Make sure that the lines are completely air free. It toook a while on mine.
resurrected_jimmy
1/2 ton status
you absolutely have to bench bleed a master cylinder on one of these, I can't remember te specifics but I believe it has what's called a quick take up piston wich is a pain to bleed
my experience with this system; the only way I was able to get it to bleed fully was to pressure bleed it...... I hate gm factory brakes......biggest fubar'ed pos I have ever had to deal with, you don't wanna know how I really feel about it
Good Luck
my experience with this system; the only way I was able to get it to bleed fully was to pressure bleed it...... I hate gm factory brakes......biggest fubar'ed pos I have ever had to deal with, you don't wanna know how I really feel about it
Good Luck
Usally the ABS unit has a bleed screw on it too, and that needs bled. At least my wifes '94 Dodge Spirit did. Replaced a line and couldn't figure for 1/2day why the pedal was still so mushy after bleeding. Finally after checking a service manual (mabey I should have done that first), saw the bled scew on the abs unit, followed the instructions and she firmed right up.
There is deffinitely no vibration so I don't think the ABS is ever kicking in. If the pressure was low from a bad master cylinder would that prevent the ABS from turning on? Where are the ABS sensors? After doing a hard stop when I release the brake there was a clicking sound coming from the passenger rear wheel area.
As far as I know, none of the lines have every been opened so I'm not sure why there would be air in the system. It does feel like air in the lines though, so I'll try the brake bleeding suggestions. If I put in a master cylinder I'll make sure to do a thorough bench bleeding first. Thanks for all of the input.
As far as I know, none of the lines have every been opened so I'm not sure why there would be air in the system. It does feel like air in the lines though, so I'll try the brake bleeding suggestions. If I put in a master cylinder I'll make sure to do a thorough bench bleeding first. Thanks for all of the input.
kd7kmp
Registered Member
I went through this same experience when I bought my '90 1500 burb last year. I thought it was the master cylinder as well. I changed it (did all the bench bleeding, pressure bled the whole system, etc.) and the brakes were the same. I ended up replacing nearly every component in the brake system. There were a couple things that helped the most--adjusting the rear brakes and replacing the front rotors. Those two things made the biggest difference. I am glad to have all new stuff for the brakes, but I would start with those two things first.
Kevin
Kevin
Dallin said:
a bad master cylinder will not cause the abs to not turn on. the abs turns on when a wheel locks up or is starting to lock up. a bad master cyl. may not have enough pressure to lock the brakes. the abs motor/control module is located directly under the driver's seat. the noise you heard probably wasnt the abs. the wheel speed sensors are part of the front wheel hubs, and the VSS provides the rear wheel speed to the abs. if the burb is high class enough it may have stability control, which can apply the brakes to prevent a skid or spin out.
ryan
