 That might be perfectly fine. The reason that you build, as the engine warms up, if it's got the proper amount of coolant in it, the radiator cap or the pressure cap, depending on what type of system, they call it different things, but either way, the cap on that is supposed to keep the pressure limited at a certain area. Typically, it's going to be, let's say, around 14, 16 pounds, some of them 18, 19, 21 pounds.