That's a good question. I had a similar problem with my van until I sold it.
Check the thermostat. Open the radiator cap and start the engine, allowing it to warm up. Look in the radiator. You should see the coolant moving. If that looks good, it might be a blown head gasket. With the engine running, place a balloon or plastic bag over the radiator opening and ensure it seals. The balloon or bag should fill with air very very extremely slowly. If fills fast, you've got a blown head gasket.
Monday, May 11th, 2015 AT 2:52 PM