I'm wondering if there will be any negative affects, if I put one of my 15/16 master cylinders in my car with the stock CX brakes. I'm wondering because yesterday and today it has started to lose pressure, but if I pump the pedal the brakes come back a bit. I'm also going to try just bleeding the system, is there anything else I should check, besides the lines of course. Thanks

 

try bleeding it. that may be your issue. Make sure all the lines are on tight and leak free. The larger master cylinder will increase pedal effort for any given amount of braking power. Read up on fluid dynamics. More surface area at the force applied side means less force applied on the work side.