The answer to 'evaporator coil making loud noise' is that a loud noise coming from the evaporator coil is usually a sign of a problem that requires professional attention. Common causes include a failing blower motor, a refrigerant leak, or a problem with the coil itself.
If the evaporator coil is making a loud banging, clanking, or screeching noise, it's best to call an HVAC technician to diagnose and repair the issue. Attempting DIY repairs on the evaporator coil can be dangerous and may cause further damage to the system.