It's good to see you back on here again. 
It could be 3 things: air in the lines, no fluid, or the piston in the brake master cylinder isn't sealing. Plus on your C, I think they have combined braking which means the rear brake also activates one piston on each side of the front calipers, so I'm really not sure how you even check if that part is working right.
It could be 3 things: air in the lines, no fluid, or the piston in the brake master cylinder isn't sealing. Plus on your C, I think they have combined braking which means the rear brake also activates one piston on each side of the front calipers, so I'm really not sure how you even check if that part is working right.