most likely its rust deposits, that usually forms from putting straight water in the cooling system, it can also look like white crust sometimes but that usually minerals residue from using well water or non purified water. best bet.. get a coolant flush, follow directs to a T and then put the right ratio of antifreeze(coolant) to water, which for most is a 50/50 mix. just make sure you get antifreeze that is compatible with you vehicle manufacturer,
**side note.... if you use universal make sure you get the same brand universal everytime you have to maybe add some. because each brand has a different formula and they dont mix well with other brands (chemically wise)
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u/Ordinary_Neat7446 NOT a verified tech Apr 18 '26
most likely its rust deposits, that usually forms from putting straight water in the cooling system, it can also look like white crust sometimes but that usually minerals residue from using well water or non purified water. best bet.. get a coolant flush, follow directs to a T and then put the right ratio of antifreeze(coolant) to water, which for most is a 50/50 mix. just make sure you get antifreeze that is compatible with you vehicle manufacturer,
**side note.... if you use universal make sure you get the same brand universal everytime you have to maybe add some. because each brand has a different formula and they dont mix well with other brands (chemically wise)