Wow!, Sampath did you remove the wheel cylinders and check for any rust? and check the washers. when i got the Vitara, recently overhauled the brakes and for my surprise, both rear wheel cylinder washers were leaking, Front left side Piston is corroded but not leaking, since agents didn't carry the parts, i have ordered them online. looks like the previous owner didn't even care to change the brake fluid and hence the consequences. and That Brake fluid can very similar to Seiken Brake fluid, perhaps Seiken is the Supplier for Mitsubishi?