Radiator fluid not being sucked back into the engine when it cools

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@AJ321 What is “Tester’s head gasket fix?” Stuff you buy at the drug store to put in the coolant and he and others swear by it as a last resort try before dumping the engine. I don’t remember the compound anymore but you can do a search here for his comments on head gaskets or he’ll pop in and tell you if you really need to know.