CRX Spongy / No Brakes

Anyone have any suggestions for this? I have a 91 CRX and the brakes are firm with the engine off, but slowly go about halfway to the floor. Engine running, the brakes go to the floor all the way; Here are the observations:

No external leaks or drips obvious
Brake pads still have pad life
Have not opened up the system and the master cylinder is full (no usage)
No signs of cracked hoses or leaks

Can air still be introduced into the system without opening up the system? The fluid probably needs changing....As far as I know the booster has never been replaced or the master cyliner (car has 170K). Thanks for any info you guys can provide...

Bad master cylinder

Bad master cylinder

X2

But first try a fluid flush/change and see if that helps any to get rid of the air. From my experience the MC's on these cars don't last forever and need replacing some time or another.

wouldn't the booster be the more likely problem since the brakes get spongy when when the engine is started Usually a master cylinder problem will make the brakes spongy even with the engine turned off

me bad I didn't read the post properly..:screwy:

That's what I was thinking Viper, but I'm not sure...? The pedal goes all the way to the floor when the engine is running, but is firm when the engine off..


wouldn't the booster be the more likely problem since the brakes get spongy when when the engine is started Usually a master cylinder problem will make the brakes spongy even with the engine turned off

if it only sinks to the floor with the engine running thats what I would suspect. But I re read your post and it said the pedal is firm but slowly sinks to the floor with the engine off

http://www.crxpower.net/~silverkorn/manuals/CRX_Workshop_Manual.pdf

look for the heading "booster"..this site has tests for the braking system and should help you narrow down the cause

watch your rpms when the pedal sinks...usually a bad booster will make the idle shoot up to compensate for the vacuum leak a bad booster will create..otherwise it must be the mc...or the back brakes aren't adjusting