Frank, My knowledge of your brake system is squat (I have a 66/300). I had a similar problem when I converted to discs a while back. Turned out the compensating port in my new dual compartment master cylinder was blocked (which kept pressure in the brake lines). The 66 brake push rod has some adjustment. Not sure about yours. I fiddled with the length adjustment of the pushrod until the compensating port was clear. Also a few moons ago I bought a rebuilt master cylinder that had a faulty residual pressure valve, which also caused a similar problem. Jack ------------------------------------------------------------------------ > From: "Frank Bakanau" <FBAKANAU@xxxx> > Date: Thu, 8 May 2003 17:23:36 -0700 > To: "chrysler" <chrysler300@xxxxxxxxxxxxxxx> > Subject: [Chrysler300] Master Cylinder Acting Up > > I've replaced the wheel cylinders on my C-300 and flushed the system and > replaced the fluid with silicone type. (I like the silicone brake fluid > cuzz it does not absorb moisture which we have a lot of here on Oregon.) > But after I drive the car a bit, the petal gets very hard, the brakes drag > and the stop lights stay on. Hmmm.... So I just crack the fitting loose on > the master cylinder, I get squirt of fluid and all is fine for a while. I > suspect it's a check valve problem in the master cylinder, but before I go > tearing into it, anyone have sage advice? > > Frank >