Re: 2004 4.7 engine reliability
The 4.7 is a reliable engine, when its well taken care of. The 2004 model doesn´t show real oil pressure, it only shows if there is pressure or not, like a low oil pressure light. There is no oil pressure sender, but a low oil pressure switch. Quite common for this switch to fail after many years of use.
Regular oil changes and changing of the PCV valve will take care of any sludge formation. I have now 220K km on the clock and only had to change the valve stem seals and the oil pressure switch.