Re: new parts same problem.
How's the temperature of the car? does it run hot/cold?
Usually the higher RPM of the water pump isn't enough to cause excessive pressure/overflow/coolant spewing from cap..
A bad cap or leaking bottle would typically leak any time the coolant is warm/under pressure
Does the bottle look cracked where the coolant cap screws on?
Could be a pressure leak elsewhere in the system, or an issue such as head gasket..
2012 IS F Blue IS F Sport
2006 Mustang V6 wannabe