What tdo the radiator core tubes look like? Are they pinched off with deposits? If so, that could be the root cause of the overheating. You may now be seeing a head gasket leak caused by the clogged radiator (or whatever) and its the exhaust gas pressurizing the cooling system that is pushing the coolant out of the overflow tank. Do you have a temp. gauge? If so, does the coolant overflow first, then the temp rises or does the temp rise then the coolant overflow (i.e. boiling over)?

Here are some troubleshooting ideas:

http://www.arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm

r.c.brown@ieee.org
TruckEditor@tlca.org
Project: 4Crawler
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