I have to change the oil pump of my 2004 titan

scan vehicle for codes --also since know of over heating problem may have fried motor

How about the high voltage coil, the high voltage wires to the distributor cap, the cap itself and the rotor inside. Any one of these could be the problem.

if is a diesel one then yes has a filter under the primer pump in the engine bay, has 4 or 5 hoses connected to it, if its a petrol it has an intank filter on the fuel sender unit, should never need to be changed. and i think the only way to change it is to replace the sender unit in the tank which includes the pump, gauge float etc...

In that truck you can use a grade like regular[ 5-20] -[10-30] it wont hurt to change oil unless the manufactors call for it.

hi, did you observe the arrow on the pump. fuel pumps fuel only one way. arrow must show from fuel tank going to engine. fuel filter is the same. gerry

Ok 3 questions to answer:

1 yes the pump could be bad, but it is not likely.
2 yes it is in the oil pan.
3 yes you can change it without pulling the engine, though it is not easy.

Most common problem for your oil pressure reading to be going away, is the oil pressure sending unit(sensor) it is located next to the oil filter, check and replace if neccessary this sensor first and see if your oil pressure returns to normal. If not then you may have a pump problem. Hope this helps, let me know.

This is natural and normal. As long as you have oil pressure and the oil, when checked on level ground, is filled to proper level you should be ok. Try doing an oil change and see if that affects the problem.

how many miles does it have , sounds like a rod bearing is bad or has turned , get the knock diagnosed to make sure

it is an internal part of the motor.

it is common for the oil pump to go bad after changing the timing belt.

the pump is located in the oil pan, and nothing drives it, it works as a sucking action....