CRX Master Cylinder?
 

So if I'm sitting on a downhill stoplight, the brake pedal slowly sinks toward the floor, meaning I have to apply more pressure to keep the car stopped. If I let go of the pedal and apply the brakes again, its engagement point is normal, and overall the pedal feels normal and the brakes seem as strong as they ever have.

I checked the fluid and it is at the full mark. Seems to me this is my master cylinder leaking a little. Any opinions?

Thanks for your help.

Yes- that's the classic sign of a master cylinder internal seal leaking- Pedal sinks under light pressure, holds better under heavy pressure.

The internal seal leak just lets the brake fluid pressure back into the reservoir. Overall no fluid is lost.

Better fix it ASAP or you might rear end someone...

Yup, just had to do it on the Del Sol, make sure you bench bleed the new MC, and if your fluid is dirty its a good time to bleed the whole system...if you do that make sure you do them in the correct order! GL Matt

The seals on the master cylinder plunger are getting worn out and allowing fluid to leak past. Pumping the pedal will help build up pressure. The only way to fix it is to replace the entire master cylinder. I have drove quite awhile like that just double pumping all the time, but that does put a lot at risk.

-Edit .. i guess i didn't type fast enough before the other replys :)

Thanks guys, that's kind of what I thought but didn't want to replace it for nothing.