My 2005 Equinox has started pushing coolant out of the overflow reservoir (no radiator cap on this model) after driving but never indicates that it is overheating. Not sure if I am dealing with blockage? Bad thermostat?

 

Try replacing the coolant reservoir cap. If this doesn't fix it and you are using at least a 50/50 blend of coolant & water, then you probably have a bigger problem such as a bad water pump or even a blown head gasket.