First, you need to make sure the cooling fan is coming on. Try turning on the a/c (if it works) and look to see if the cooling fan turned on. If the a/c doesn't work, warm up the engine and see if the cooling fans comes on (take care not to overheat engine).
If this works, then touch (be careful almost everything will be hot under the hood at operating temperature) both the upper radiator hose and lower. If the water pump is working you should feel similar temperatures between the two hoses. If the pump is not working there will be a difference between the hoses but make sure there has been sufficient time to allow the thermostat to open up allowing coolant to flow through.
Last you will need to have the cooling system tested for combustion gases which your probably better off leaving that to a professional. Also, if there is a leak causing combustion gases to enter the cooling system it will cost quite a bit to have it repaired. So that being said, take care not to allow the engine to over heat because it will cause damage.
One thought came to me. Could it be possible that the thermostat was installed upside down (spring side on the thermostat facing up in the housing)?
Try this and get back to me.
Wednesday, October 9th, 2013 AT 6:40 PM