i think possibly you might not have even a bad head gasket.

i would try flushing it out first. this could be residue from the wrong antifreeze. the pushing it out of the tank could be just from a bad rad cap, perhaps. you don't sound as if you have any other symptoms pointing to a bad head gasket.

your mechanic might be a bit too eager in this case.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.