Samguy2000

Hello, I have a 2004 Chevy Express 1500 AWD 5.3 V8 with currently (01-07-2023) 161,xxx miles. I'm up here in Fairbanks, Alaska and the water pump was leaking like a sieve (from the weephole apparently) so i had that replaced at a local shop ($800) and I recently did the oil change myself.

Tonight, 01-07-2023, I left the house to go to Costco and and then drove back to the house and left it parked outside idling, when I got back in and put the gearshift into Drive, I started hearing this humming/vibrating noise that would get into higher rpm the harder I pressed the gas pedal. I quickly drove back to the house driveway and parked it for the night cause I didn't know what was going on. I tested it out again and with the van in Park, I pressed the gas pedal again and I still heard the noise. Does anyone know what may be causing this?

It is worth noting that on the repair order from the shop that did the water pump, they used their scanner to see what the codes were and there were these codes:
P0101 - Mass Air Flow
P0106 - Map or baro Circuit out of range
P0108 - MAp or Baro press signal high
P0430 - Catalyst Eff Low Bank 2

A previous mechanic told me that these types of codes are just O2 sensor codes and it is not worth dropping the gas tank just to get them, but the shop that did the water pump laughed at that and said no that could cause a bunch of other problems.

I was told by some people I asked tonight that it could be a misfire and to possibly check the spark plugs (and get new ones) and also coil packs? Also could be ice buildup in the wheels.

mountainmanjoe

can you record the sound and upload it to Youtube?

Any idea where it's coming from? Is it louder under the hood?

Samguy2000

Yes, I can record it. Will do so in the morning. I have no idea if it will make the same sound when I start it up first thing today. i will make sure to check the fluids (oil, trans, coolant, etc) just to be sure. I don't think misfires just go away by themselves do they? And yes, it sounds like the sound is coming from underneath the motor cowling in the van (beneath the firewall) Will shoot a quick video and upload to YouTube or Imgur or something later today (it's currently 12:08 a.m. here)

mountainmanjoe

check the air filter while you're at it

Samguy2000

air filter was good last time I checked it. what would I be looking for? how dirty would it need to be?

mountainmanjoe

ok ... and "last time" means yesterday? 10 years ago?
You're looking for dirty, plugged up, or damaged filter. put a strong light into it, and compare to a new one.

Samguy2000

YouTube link -

mountainmanjoe

It sounds a lot like a loose exhaust heat shield

Samguy2000

added some PS fluid to the reservoir and turned the van on. There was almost no noise this time. I turned the steering wheel all the way to the right and left so the fluid could push out the air. I then took video of some hose leaking under there, so now I know where it's leaking at. That explains the glistening fluid mess.

Samguy2000

Well folks, turns out it was the power steering hose leaking. Apparently a common problem up here in Fairbanks, Alaska. Took it to the shop and they put an Arctic grade power steering hose on it. Problem solved. For now....