Yes I have this thick yellow slush in my coolant tank on my

It needs to be flushed and you need to check for oil leaking into cooling system, possibly from a blown head gasket or leaking transmission cooler. "Block Tester" can check for hydrocarbons in the coolant, a byproduct of combustion gases that can find it's way into the radiator from a blown head gasket.

That sounds like a mix of oil and coolant. You likely have a leaking head gasket.