brake issue!

medic · 04-06-03, 11:23

So my friend and I finally changed my front brake pads, rotors, and calipers on my 93 maxima SE yesterday. Everything seemed to go well and we bled the brakes until there were no more bubbles and new fluid came out, but when I started the car, the pedel felt really mushy. I had to press the pedel down to the floor to keep the car stopped even in idle. We figured air in the lines, so we did it again the same way - LR, RF, RR, LF as indicated in the factory service manual. We pushed the brake pedel several times, kept it held down, opened the air bleader valve to let air into the bleader kit, closed it, and the released the pedel. We did several times for each wheel, but there was no air - only new fluid. We've done the whole bleeding procedure about 5 times now, and there was no air we could see coming out of the lines after the first time.

What's going on? There are no leaks either. The only strange thing (I think) is that is when pulled the vaccum tube that runs from the brake booster to the valve the brake pedel feels normal. We replaced the valve thinking it was bad, but when we replaced it with a good one there was no change in the brake pedel feel.

Neither of ius have any ideas what it could be. The brakes were working fine before. I used Castrol brake fluid which says it exceeds DOT3 and DOT4 specs, Raybstos quiet stop pads, pro stop rotors, and pro stop calipers. My break system recomends DOT3.

bretfraz · 04-06-03, 11:40

GeekySteve and I replaced front pads and flushed the fluid on my car last October. We experienced the same thing. After a few days of driving the feel and pressure came back.

A lot of times what happens is the caliper pistons retract too far into the caliper itself so when you use the brakes the piston is not travelling the same way it was before. I think after some driving the piston repositions itself.

BradE · 04-06-03, 12:28

Well, it could be many things. The first things that comes to mind are the master cylinder or power brake booster might be on the way out. Especially if the pedal feel was fine, then dropped off all of a sudden. Are you totally sure there are no leaks allowing air into the system?

geekysteve · 04-06-03, 01:32

It's also possible that the parts store got you the wrong calipers, or you've got a bad caliper. For a period of a few weeks back in the early 90's, Ford had incorrectly listed a caliper application for the Tempo (eeek!). The caliper fit fine, looked right, but something with the internals was wrong (like piston size or valving). The brakes were horrible - worse than before we'd work on them.

You might want to triple check with the parts store, and maybe do some cross-checking with other brands. It's also possible (highly unlikely) that the vacuum booster was damaged during bleeding (over enthusiastic pressing on the brakes could have torn the bellows)... unlikely, but anything's possible.

medic · 04-06-03, 03:32

I just took the car out for a spin, and to does stop but just takes a long distance. Even if I mash on the brakes from 50mph, the car won't skid (and I don't have ABS). If I pump the pedel quickly, I build up pressure and the pedel feel returns for a moment, but it fades quickly.

Any way to test the master cylinder or booster?

BradE · 04-06-03, 03:39

I just thought of this, often times a Master Cylinder will have a bleeder screw just like the calipers. Check to see if yours does and bleed it. That might be causing your problem.

medic · 04-06-03, 04:47

we made sure that the master cylinder had fluid in it at all times during the bleeding process, so I don't think there could be air that came in from the master cylinder. we filled it up to max each time we bleed a wheel and it never went below the min level

showroom, I'll need to check on the master cylinder bleeder valve - it didn't show one in the fms, but it didn't mention half the stuff people have suggested thus far.