coolant spilling out cap

Hello all. I realize this is a boring topic but I need help as I am pressured for time. I recently had my radiator flushed out professionally. When I stop after driving for awhile, coolant will surge out the radiator cap! (sometimes) There is no indication of the temperature being out of range as far as I know. I guess it could be a faulty cap but I wonder if anyone out there has had a similar problem. Please reply fast!!

Replace the cap. They cost like $6.

The new Stant radiator cap had a problem too because it didn't grab the filler opening very well so coolant still came out after stopping but for a different reason than the old cap (this couldn't be simple, could it). I bent the parts that are supposed to hold the cap on to make it tighter and all is well now. I don't think this is a very good quality cap though. Thanks for the reply.

That is why it is 6 bucks. Mine was made in Mexico.