2000 Pontiac Montana Van- intake manifold has been replaced along with radiator, water pump, radiator cap and thermostat. When driving van will go to the red line but has never overheated with steam and such coming out of engine. It doesn't show signs of blown head gasket. Radiator and over flow are still full. Service engine light has been on since intake manifold repair. Air has been bled out of system quite a few times. Any help would be appreciated.