brake components:
95VTEC Prelude... new stainless steel brake lines, bleeded and new fluid, bambo disc, and new pads.

fluid:
checked the fluid, normal filled to the max, no decrease after use; no leaks

problem:
1. brakes are fine normally,
2. but usually after an hour or so of bumper to bumper rush hour traffic trying to get back in NYC right before the Lincoln tunnel, the brake paddle gets really soft... have to pump.
3. it started doing that when the car is slope down, is this another factor for the soft paddle?
4. soft paddle for the rest of the drive home
5. next day, brakes are fine and strong when i'm heading to work
6. soft paddle cycle begins again, back to 1.

Questions:
what's the problem?

what if there is air inside the master cylinder? this cause this slop-down soft paddle?

how do i check for vaccum leak? if there is a leak, what needs to be replaced?

solutions?

suggestions?


thanks!

 

your brakes are probably overheating.
once brakes heat up, they dont work as well.

 

How do they behave? Slow & smooth sinking to the floor with moderate pressure? Or soft pedal that stiffens up when you pump it?

Slow & smooth sinking to the floor is a bad master cylinder. When the piston seals start to go bad, they often act up only when they get hot. Then they start doing it all the time. Flushing with fresh fluid sometimes works, but the problem comes back.

Soft pedal would be air in the lines. Bleeding usually fixes it. Since you have new SS lines, maybe there's still air hanging out. When the system drains, I usually have to bleed LOTS of fluid thru, like at least a pint at each rear wheel.

 

yea, slow and smooth sinking to the floor
i just hold the brakes at this position, and it just sinks all the way down,
then i have to release it for the paddle to come back up and do the same thing again.

 

Classic! Buy yourself a new master cylinder.