09-10-2014, 09:39 AM 
	
	
	
		Master cylinder seals do wear over time, not surprising really with a piston sliding past them several times a day, and if any shite gets in the brake fluid (grit/rust) obviously that can cause damage to the seals.  That'd be my guess tbh, though it seems odd that you can get a firm pedal with the engine off.
	
	
	
	

 
 

