so far it has had new 3 way valve thermostat expansion tank cap replacement radiator new water pump full coolant system drain and flush.about 18 months ago it had hg replaced head was skimmed new head bolts truck had only covered 6000 miles before i bought it so hg doesnt sound like its the problem has anyone else had similar?it has been suggested the block is porous. im at wits end because heater blows hot and cold sometimes system works ok other times pressure bulids up have had a cream expansion tank split yesterday
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