Odd Rear Caliper Drag
I currently drive an '07 3i with 107k miles, this is my 3rd Mazda3 and I am a very capable mechanic doing all my own repairs, but this one has me stumped. I was teaching my cousin to drive stick shift a few months back and the dummy decided to pull the parking brake while moving at about 50mph (to much video games?). Driving home I notice the car feels sluggish, a little harder to get rolling in 1st from a stop and as I continue driving poor fuel mileage. I do A LOT of highway driving and went from a 35mpg avg to 27 mpg avg over the last few months...somethings not right!
I pull the rear wheels to make sure everything is moving correctly; clean & grease the pins, reset the pistons & pads, parking brake cable appears to be moving freely, and put her back on the ground. The car is fine for the 1st 50-100 miles then the dragging comes back, double check everything and the same problem creeps back.
When I purchased the car a year ago it had pitted & gummed rear calipers that I replaced....so I contact the company and warranty these thinking the piston or ratchet got bent up and is jamming. New pads, new mount/pins/calipers. 100 miles later the brake drag is back. I had a new dorman parking brake cable in my box-o-spares so I take the hour to swap out what's probably a rusty mess of the original cable. 100 miles later the brake drag is back.
Its better, but still not like it use to be. I'm able to eek out 30 mpg by babying it, but you can still feel the car pitch forward as soon as you let off the gas. I've replaced all the mechanical parts with out solving the problem. Is it possible to damage the Master Cylinder by jamming on the parking brake? Old rubber brake lines that are partially collapsed and not allowing pressure relief?