Hey, my cooling system has alot of rust/mud looking crap in it, and I'm about to fit a new water pump (as mine is leaking) so I'd like to give it a good flush out before hand. It's not just in the radiator, it's definatley in the block too. I'm not sure if I should buy one of these radiator flush additives, or just do it with a garden hose. Any advice/ideas would be appreciated.

Gab

get it hot and flush and rev flush,heater as well,get the crap out.then fill and add a cleaner for a few days,then flush.may have blocked the radiator by then or before.add the rust inhibitor,your choice.

Drain the existing coolant/sludge out of your radiator by removing the lower radiator hose, refit the hose when it's done draining and fill the radiator back up with water and add some radiator flush out. run the car to operating temp and once again remove the lower radiator hose and drain the fluid again. Wait until your car is cold before refilling! ...To make sure you get as much of the sludge out as possible you could remove the thermostat and lower radiator hose and stick your garden hose in the thermostat housing to flush the coolant out of the head & block and you could also do the same with the radiator by removing the top and bottom radiator hose, then stick your hose in the radiator where the the top hose joins up and intermittently block and unblock the lower outlet of the radiator with your hand so that the radiator fills up when you block it then drains when you unblock it. Keep flushing water through the radiator and head/block until clear water comes out. Then reinstall your thermostat and hoses...

I'd recommend refilling with a good quality concentrated coolant mixed 50/50 with water.