My dad's 2012 F250 CC 4x4 6.7 is making a funny noise after shut down. He had it in the shop when it was still under warranty and the changed out a hose that is associated with a solenoid that stays on after shut down. He said that quieted it down at the time somewhat, but now it has started making another noise. He says he can hear the noise from the solenoid but now after a few seconds it makes a burping noise. Is this anything for him to be alarmed about?