Good way to clean rust out of coolant galleries?

[jono035]

Have pulled the heads off the VFR ('90 VFR400 NC30) this weekend to just generally have a look around and do a partial top end fix-up due to way-too-tight valve clearances and found orange rust caking all the coolant galleries. It dumped a heap of sludge that was probably as old as the bike when I first checked the clearances a few weeks ago, flushed it out for half an hour with the hose and put fresh coolant in. The coolant still looks like new, but there is a layer of orange rusty looking crap over all the galleries.

Anyone got any good tips or tricks for this? I've noticed a few rust-remover flush type products, anyone have any experience with these and know if there is anything to watch out for with them?

Also, anyone know where that rust could have come from, I didn't think aluminium rusted that way and it seems like it's just gunk stuck to the surface, the surface underneath isn't pitted...

Also, does this even need cleaning out or it it a case of 'it aint broke, don't fix it'? I just went out and checked the water pump, it looks like the cleanest part of the entire bike actually...

Edit: The 2nd pic is of the thermostat housing, it's already had a heap of the crud scraped out of it. Also, if anyone knows why there is still coolant in the bore jacket then I'd love to know if there is some trick to getting these things to drain completely...

Edit 2: It just occurred to me that the reason the water pump looks so clean and shiny is that it must have been replaced, which means the orange crap everywhere is probably the original impeller that has rusted, been mulched and then carefully distributed through the entire cooling system... Great...

http://www.evapo-rust.co.nz/Cooling%...em%20Flush.htm looks pretty interesting, $70 for 5 L though...

[schrodingers cat]

I wouldn't fret about it too much. You're already doing the right thing. Try some of the aftermarket coolent system flushes and give it another couple of good hose outs sane as you've done.
The thing to be suspicious of is how efficient the radiator is now as there is probably a bit of shit stuck in there...