car is overheating, overflow empty. Is there a radiator cap? on 2000 Pontiac Grand Am

I dont see a radiator cap on the radiator is there one? if not how do I check the coolant level?

Asked by for the 2000 Pontiac Grand Am
The overflow is your coolant level check with the marks on the side of the whitish plastic. It is a pressure system. The only way to refill is through the overflow tank. There is no radiator cap.
1 more answer
i have the same type of car and the over flow tank has been the only spot that i have found to add coolant but i am fighting a problem as well with mine where the over flow tank actually builds to much preasure and there is no leaks on the out side of the car for as to where the coolant is going but it seems to be gone right away if i leave the over flow ca off it coolant will over flow the tank then it sucks it in to the system and its gone til car heats up again then itll over flow that tank again and just keeps doing that if any one knows whats happening or has any suggestions on how to tell whats going on please let me know thank you