I had my rad changed back when I was at 15,000kms due to a crack in a bracket between the ac and rad. After that I started noticing some black stuff in my dexcool. took it to dealer they said car is fine last dealer must of had some dirt in coolant the changed the resivour and topped up the coolant this morning i noticed some black stuff again. (crums not oil) I wanna open a hose let all the coolant out and do a full refill. Anyone know which hose or hoses to remove to get the most out?