Hey guys--

My mother's fort tarus has filthy coolant (rust colored) that was just
flushed from the system.  Its immediately dirty again, right after being
added and run for a few minutes.  Local mechanic says that that radiator is
probably rotted/rusted out, which seems about right.  

Recently however, another point was brought up, the possibility that the
corrosion has spread to the engine.  Are there any good tests or rules of
thumb to test where the problem is before she spends 250 on a radiator and
500 for a heater core?  Thanks to all who may answer.

Omar