Replace it with a new genuine oem factory brake master cylinder cap.
2006-2013 Mazda 6 Brake Master Cylinder Reservoir Tank Cap OEM NEW GP7A-43-55YA
2009-2013 Mazda 6 Brake Master Cylinder LQ85W
03-07 SILVERADO SIERRA LB7 LBZ LLY 6.6 BRAKE MASTER CYLINDER TANK BOTTLE T3204
For Mazda Miata Brake Master Cylinder w/ Reservoir & Sensor 1990-1997 1.6L 1.8L
For 2011-2012 Mazda 2 Brake Master Cylinder Dorman 39467VDRK
For 2011-2014 Mazda 2 Brake Master Cylinder Dynamic Friction 63963WY 2012 2013
