Check coolant level in radiator cold engine, then oil in warm engine.
Then press on and move around, the PCV valve. Pressing PCV valve into rubber grommet (98-02). Over time the rubber grommet, hardens and shrinks. Air passing, can make sounds, so can a fouled PCV valve. Check for other vacuum leaks, while at it.
Make sure AC off. Helps eliminate AC compressor
Then remove fan belt.
If above all good. Start engine while fan belt off. You can run engine for a few minutes, with Fan Belt off. Water pump and timing belt pulleys, will be running/spinning. If sound still present, needs a proper Timing belt service.