My brother's 3.4L camaro has started to over heat. He replaced the thermostat and all the heater hoses. There isn't any external leaks. The mechanic say says could either be the head gasket or the water pump is on its way out. The oil is fine. What's the likely hood of of the head gasket being bad?

 

Is the top hose getting big and swollen while the bottom is cool? That would indicate a problem with flow. If not test compression that will tell if its something in that area.

 

Is he losing coolant?

 

He didn't say. An the last time I asked him questions my father jumped down my throat so I have to wait till he's not home.

 

You can check the oil cap to see if there is moisture on it, after it has been ran for a bit. Then that might indicate that coolant is getting in the oil.