just noticed yesterday whilst driving on me break from work that it was slowly leaking. now its not round the edges it coming in where the handle is to twist to open it up, its not done it before and ive driven alot in rain but its been raining alot so maybe thats why its started basically just wondering what i can do to fix, buy new rubber seal for that part? thats only thing im thinkin. not great when im looking to sell next month

rubber seal..
blocked drain holes..

usual suspects

how much am i looking at? and best place to buy them? dont think want to bother 2nd hand because may likley end up in same situation in few months down line well the new owner will do and id rather buy best i can for state of mind

try cleaning them up a bit with some white spirit etc to get rid of any crap thats on them.. free option