The thermostat in the Lexus LS 470 stuck closed (I thought they engineered those things to fail open now), and the head gasket blew.. Took it to my mechanic, who replaced the head gasket and milled the head, now there is an obvious valve noise, and according to my sister (the driver) an occasional knocking. Took the car back to the mechanic and complained but he seemed to believe nothing is wrong, said he did not have the valves adjusted as it would cost several hundred dollars extra. Could somebody shed some light on perhaps what was done wrong?
