Now, I have a problem and need some advice. My 66 Cuda has a standard manual master brake cylinder. Several months ago, my brake pedal went ‘hard’, and the brakes started to drag (rear brakes especially), really bad!

This past Sunday I bled the rear brakes. They bled fine, and the pedal is no longer ‘hard’ as it was before. But while bleeding the rear brakes, I found that after I depressed the brake pedal, it would not return on its own and I had to pull it up using my toe. I can’t recall that happening before. Could there be a problem somewhere, and if so, any ideas?

I rebuilt the entire brake system back in 2000, from the Master Cylinder to all four Wheel Cylinders and all plumbing in between. Since I don’t drive the car as much as I should, could something just have gotten stuck? I plan on bleeding all wheel cylinders this coming weekend until I get clear fluid flowing from all wheel cylinders. I am open to any other suggestions

Yesterday was the day I took a hard look at my braking system, and found that there was a large accumulation of rust and corrosion in the master cylinder.

Flushing the master cylinder didn’t help, so I had to drain and clean it thoroughly. After refilling the master cylinder with clean brake fluid, I then bled all wheel cylinders, pumping at least 16 to 24 brake pedal pumps per wheel. I then took the car out for a test drive (and fuel!), and estimate the drag has been reduced by at least 80% in the rear drums, and 100% in the front drums. After a good 15 minute drive at about 30-35 mph, the front drums were cool to the touch, and the rear drums were warm, but not hot. Yea! I intend to cautiously exercise the brakes for the next couple of weeks, and then bleed the entire syste m again. Hopefully that will loosen any corrosion build up in the wheel cylinders, and I can just flush it away. I really don’t want to disassemble all four wheel cylinders unless I have to!

Brake fluid and cast iron just don’t get along too well. Even though I rebuilt the entire brake system nine years ago (rebuilt master and wheel cylinders, new brake shoes and hardware, all new brake lines and hoses), the amount of corrosion build-up found in the master cylinder was really depressing.

I would suggest that if you don’t drive your old Mopar on a regular basis (or any vehicle for that matter that uses cast iron brake components), you may want to consider flushing your brake system periodically. Too bad they don’t make a corrosion resistant brake fluid, or if there is one, I haven’t been able to find it. A few years back, there used to be a DOT 4 rated brake fluid that was supposed to reduce the amount of corrosion build-up as well as increase the boiling point of the brake fluid. Back when I had my ’73 340 Duster that’s what I used, but that’s been over 10 years ago now.

I would not recomend switching to dot 4 or 5 unless I replaced all the rubber hoses and wheel cylinder and master cylinder. I have seen several people attempt to flush there systems of dot 3 and then go to 4 or 5 and end up with problems. For what ever reason once the dot 3 has been in the system you just can't get it clean enough for the dot 4 or 5 conversion. This can be a real bad seen especially if you are running a single system brake setup. the rubber parts just seem to swell up a become useless.

With the silicone brake fluid, you'll definently find out how good your connections are... We used that on an old car and ended up with some leaks. We drained it all back down and used Dot 3 and had no problems. I do agree that Dot 5 will hold up better and may be a little less corrosive on your brake system.

DOT 4 is FULLY compatible with DOT 3. No flushing needed (but it's a good idea to get the old stuff out) Highly recommended is Castrol GTLMA for ABS, disk and drum brake systems. (LMA) stands for Low Moisture Activity. Meets specifications : SAE J1703, FMVSS/CMVSS No. 116, DOT 3, DOT 4 motor Brake Fluid.

DOT 5 on the other hand is a different story... I have been using it in my 65 cuda for a number of years now with NO Problems. I however did replace all the rubber parts in my system... At the time I also was installing all new Stainless Steel lines, new Wheel cylinders and new dual bowl MC. DOT 5 is a silicone fluid and is NOT compatible with DOT 3 or DOT 4... If DOT 5 mixes with either DOT 3 or DOT 4, it will jell and you WILL have problems.

The Valvoline DOT 3 / DOT 4 brake fluid is also an excellent choice.... Minimum wet boiling point is 311°F. Castrol GTLMA DOT 3 / DOT 4 has a Minimum wet boiling point is 329°F And, BOTH are "Synthetic" (That's a good thing). My point is don't buy the CHEAP stuff! And... NEVER mix with DOT 5 (silicone) !