Dirty water staining on gearbox after burst pipe

Hi there people, I've just had the water pipe that comes off the side of the head burst, it has left me with a dirty water stained gearbox, there was abit already there from the past when the metal waterpipe has split, not when I've owned it mind, anyway, is there anything that gets this off easily? I've got some gunk that I'm slowly cleaning the block and bay with, would this work ok? I just wish I had the time and space to whip my engine out to clean properly and paint!
Thanks in advance for any tips

I have not tried it yet, but someone gave me a tip a few months ago that cleaning the gearbox and engine block with WD40 and wire wool works a treat.

I've found Autoglym engine and machine cleaner work well on most parts. Great for removing oil and grime.

http://www.autoglym.com/products/products/engine-and-machine-cleaner

I also used Autosol chrome polish in the past with good results too.
http://www.halfords.com/motoring/cleaning-products/polish-wax/autosol-metal-polish-75g