Are there any additives for flushing my cooling system?

The system has most likely never been refilled and the reserve bottle is very pasty looking. The liquid is pink, but it definitely looks well used. I assume the previous owner was just adding whatever fluid and hose water. So I want to get all of the calcium that I can out before adding the pink stuff, and a new thermostat. I was going to just drain both compartments and fill with distilled water, run the engine and flush for a while until it was clear, but I know that there will remain a lot of junk. Any ideas? Vinegar perhaps?

 

ive heard of people using cl-r, but i assume there must be an automotive product similar to it.

 

I think it says something about "never use on aluminum" or whatever.

That may be what I do. I just thought maybe some folks here might use a vinegar and baking soda concoction.