Calcium buildup on water neck: how do I fix that?

[In The Ten Ring]

First off, how does this form? My truck's original owner told me that he only put distilled water into the radiator but if so, what is this gunk? The water hoses have it on the inside and I am going to assume so does the water jacket. The outside of the radiator has a heavy buildup outside as well so I bought a new radiator.

How do I get this out of my cooling system?

['68OrangeSunshine]

I think that L6 thermostat housing is made of aluminum, so the oxidation is normal. You might try vinegar, but a wire brush would be the most the effective.

[68c10airstream]

I believe the buildup is from antifreeze trapped between hose and neck, no new antifreeze washes in to replenish the additives and it ends up acidic. I clean then up with a stainless steel wire brush and paint the neck or I used to put #2 nonhardening aviation formula permatex sealer to be a buffer between the two. I use late model constant tension clamps because as the rubber will collapse slightly under hose clamp pressure the old style worm drive clamps would need to be retightened up every so often. Usually the clamps would be retightened after a slight leak was found, further locking in trapped antifreeze. Late model vehicles as a general rule don't leak antifreeze anymore around clamps so they get my vote.