I decided to change the brake pads and shoes on my 99OBS. Did everything normal, filler cap off, compressed calipers, changed pads reassemble everything, replaced cap, pump brakes till tight, start car

and spongy pedal goes to the floor. turned car off checked fluid, it never went back down from compressing calipers. So i decide to go ahead and do the back shoes and bleed everything. I bleed master cylinder, all 4 according to directions here(fr.pass, rr.dr, fr.dr, rr.pass) No air comes out of anything, no leaks and nothin changes... is this another $100+ mastercylinder fix? Everything seems to be $100+ for this dang car its frustrating the heck outta me. Please help.

Maybe a dum question but.....did you bleed all the calipers via their bleeders? (wasn't sure since you said master cylinder). The calipers are back on the correct sides so bleeders are at the high points? Does this vehicle have ABS?

Also did you lubricate the sliders? Are the brake pads fully seated?

 

And the biggy, when you bled the brakes, did you always put brand new fresh fluid in the master cyinder?

 

 

nipper

The proper procedure when pushing caliper pistons back is to open the bleed screw at the caliper. Otherwise, you risk forcing contaminated brake fluid back up the lines into the ABS unit and elsewhere. Once contaminated fluid is in the system, all kinds of problems can develop.

 

If you're lucky, a complete flush with fresh fluid may resolve the problem.

 

See:

http://endwrench.com/images/pdfs/BrakeFluidSumm02.pdf

http://endwrench.com/images/pdfs/BrakeSystemWin01.pdf

It could be the master cylinder, and if it is, here is what can happen. After brake maintenance, when pumping the hydraulics back up, you can stroke the brake pedal down to the floor, as the new pads need to be pumped out to contact the rotors. This can force the master cylinder rubber cups through all the junk and corrosion at the bottom of the bore where there is normally no travel. This is much more likely to happen on cars that have aluminum master cylinders and no brake fluid change outs over the years. I have had master cylinders that were working fine destroyed by one excessive stroke. It’s better to set new pads using a bunch of short strokes rather than one deep stroke.

If you just changed the pads and shoes, there was no need to bleed anything, If you opened one of the calipers lines or wheel cyclinder line then you would need to bleed that one only. What you need to do is put every thing back together and take wheels off one at a time and have someone pump the brakes while you check lines for leaks, you may have caused a leak in one of the lines when you removed caliper. If this dont show anything go to auto parts store and get a set of calipers line pinchers, and pinch one line closed at a time, if your pedal returns to normal then you have damaged the seal in that caliper when you compressed the piston back in. Also you need to address porcupine question, so we can be sure you did not bleed the brakes at master cyclinder.

I decided to change the brake pads and shoes on my 99OBS. Did everything normal, filler cap off, compressed calipers, changed pads reassemble everything, replaced cap, pump brakes till tight, start car

and spongy pedal goes to the floor. turned car off checked fluid, it never went back down from compressing calipers. So i decide to go ahead and do the back shoes and bleed everything. I bleed master cylinder, all 4 according to directions here(fr.pass, rr.dr, fr.dr, rr.pass) No air comes out of anything, no leaks and nothin changes... is this another $100+ mastercylinder fix? Everything seems to be $100+ for this dang car its frustrating the heck outta me. Please help.

Hm very interesting info NOMAD327. I will have to keep that in mind for future jobs. It probably explains why in my previous bleedings I noted that after I pushed the pedal all the way to the floor I got a lot more junk out the bleeders.

Thanks for all the replies and info. I bled the master by putting threaded hose barb connectors in the line holes and attatched hoses going to jar of new fluid and pumping the pedal slowly. Reconnected the lines then bled at the calipers on front and the wheel cylinders on back. I used new fluid for eveything and old fluid was just a little dark, no trash or anything visible. No ABS. Although i havent taken the wheels off to see if the pads are seated, i have driven it and it stops about halfass if i pump a couple times. I'm not losing any fluid, i have checked everything, the level didnt drop from when i changed the front brake pads, tho it did after bleeding of course, and its at full at the moment. I know I shouldnt need to bleed them after just changin the pads but the pedal was fine until i changed them so thats the first thing i could think to try. After changin the front pads i slowly pumped the pedal and i did not stomp on it and it was soft from first pump, and still is. Maybe i'll try flush and pull off wheels for inspection this weekend. Thanks for your input, I'll post again after next try hehe.

Its not unusual to have the master cylinder go like described above, but on a 99 thats a little to new for it to happen.

 

 

nipper

After changin the front pads i slowly pumped the pedal and i did not stomp on it and it was soft from first pump, and still is.

 

Did you push the pedal all the way to the floor? It's not how hard, but how far you push it that can trash the seals in the master. It's rare, but it can happen.

 

I'd look more for a twisted or kinked hose running to one of the calipers or a misinstalled bracket.

Say what condition are your break lines in? That can cause the same thing ... again unusual at this age but not unheard of.

 

nipper

[...]No ABS.[...]

Really? Can anyone else confirm that there were MY99s built wihout ABS?