I drive a 2006 Chevrolet Equinox and I have had multiple overheating problems so I was told it was my head gasket so I brought Bars leak and put it in now it's knocking at start up but levels out after 20-30 minutes what could be my problem? Please help

 

that stop leak stuff is a joke and should only be used in absolute emergencies. Hard to say what the noise is from...is your oil full and not contaminated?

 

3.4 L engine heads crack, burn coolant , overheat and kill the rest of the engine