Try some recommended flushing chemicals. Flush well, maybe 2 times, try to backflush and rinse well. I think some flushing chemicals you might be able to drive around for a few days. I will be trying a flushing chemical in my Jeep which is experiencing problems very similar to yours.
If that doesn't work then a new radiator is a lot better (labor and dollar wise) than a new engine and new radiator! ;-)
I think that some people have used CLR along with boiling water AFTER they remove the non-aluminum radiator so it can sit for XX minutes. CLR will supposedly eat away certain metals like aluminum. from
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"If an alkaline based flush makes you feel good, get some aluminum foil and chop it up and dump it in some plain Drano [or just sodium hydroxide]. Do this outdoors in a well-ventilated area with no flames nearby, as this is how the US military generates hydrogen gas for weather balloons. " Even the Radiator Flushing chemicals are dangerous! Be careful and friendly to the environment! ;-)
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