Oil in coolant or dirty system

took off bottom radiator hose inside black as charcoal. Oil pressure good 30-60 temp always around 170 good power no smoke out pipes does hav bad blow by no water in oil did analysys is it oil cooler or system dirty? Engine was overhauled i believe 100 k miles ago maybe system was never cleaned??? How can i tell oil cooler is bad??? Here are pics

What i did...

I bought the truck a month ago it had green coolant I changed green coolant to red coolant flushed it out real good added water so the coloring goes away went to Texas came back coolant looks like purple dark purple flushed it again added water added some cleaners from Napa for the radiator flush again went to Denver Colorado came back again same issue

 

Should i keep flushing it with water and dawn maybe that will work common guys i need your input if you experienced this and or know what you are talking about

 

Forgot to mention engine is a 1999 Detroit 12.7 series 60 with 500hp.

 

How much cascade

Thanks for reply

 

Can i just dump cascade in the coolant i already have in now?

 

And then flush with water?

 

How long should i run it for?