Long story short.
Put a ATK rebuilt 4.0L in a blown 94 XJ. The girl never changed the "dex-cool" and the old motor blew a head gasket and she kept driving....
Oh yea she broke a rod
Anyway I fushed out the Radiator and it looked good.
One prob, opened the heater valve one cold night and the next day my coolant was brown
Has to be the heater core imo.
So little by little I extracted the green/brown coolant and replaced it with 50/50 mix 8 oz at a time. After 4 months and 4 gallons of fresh coolant I am making progress!
Have you guys ever tried this? The heater is doing great.
I figure after 6 gallons and 3 more months, I may have all the crap out.