Hi guys, having an odd brake issue with my 2007 crown Vic police. This started very subtly and is getting worse. When I apply the brake it is spongy but grabs, if I let off the pedal just a bit and re-apply pressure it drops significantly. If I repeat, it will continue to drop to the floor. If I release completely it will rise back up and start over. If I apply firm pressure quickly, the brakes hold solidly. If I continue to hold firm pressure they will ever so slowly drop to the floor (almost can’t feel how slowly). I have had a car prior that had air and it did not hold firm like this, it would drop much more quickly. Is this an air issue, master cylinder, etc? I’ve been told not to do an old fashioned bleed on these cars due to their ABS module, true? Don’t have much money for full diagnostic so trying here first. Sorry for the long first post...
Sounds like abs is acting up... but could also just be the brake lines... they get old and expand and any expansion can/will feel spongy. The floor drop is master cylinder or abs. Assuming fluid level is correct and not changing...abs likely. Replace the flexible brake lines first. And can be bleed, just follow correct procedure for that car... I recommend this also to get fresh fluid as brake fluid attracts moisture and can cause the issue too after repeated stops (heat buildup causing moisture in lines to boil and potentially activating abs).
Thanks HillBilly, I’ll try your recommendations. Hopefully not the ABS...$$$. Oddly enough, I had to do a hard brake and the abs had to engage because I couldn’t stop quickly enough, I did no hits lol. Needless to say it’s off the road for now until fixed.