My 98' Volvo S70 is starting to make this weird humming noise just recently and I'm concerned as to whether or not the vehicle needs some serious maintenance done or if I should start looking for another car all together.

Here's a video showing what the problem is:

Would definitely like some feedback to the car as the car just hit 170,000 miles. Thank you!

 

The first thing I would do is stop reving the motor.

Second, undo the serpentine belt and see if you still hear the noise. If so, your idler or tensioner roller is about to fail and will toss your timing belt which will destroy the motor. You can read my timing belt info here:
Timing belt replacement instructions on a 1997 Volvo 960

When was the last time the timing belt was replaced. If it hasn't been changed in the past 70,000 miles it needs to be done ASAP. If you're not going to do it yourself have it towed to the shop to have it done or pay someone from here $200+ parts to do it. If you hear the noise with the serpentine belt off, and the belt was changed recently, they likely DID NOT change the rollers and the rollers need to be changed ASAP, with a new belt. A locked up roller will weaken the newer belt.

 

sounds like a massive vacuum leak to me.

 

That sounds terrible! I would not drive it until you figure out what the heck it is and fix it. What rspi said. A good tech with stethoscope (or screwdriver) should be able to track it down in no time...

 

Thanks for everyone's suggestions but it seems that even after the rspi's suggestion and replacement parts the car is still making the same noise.

@Lifesgoodhere: How exactly do you go about detecting a vacuum leak and fixing it?

Thanks again for the help.