Super loud whine from engine bay for about 10 minutes, then went away...

Yesterday while on an 50 mile I had much more serious whine from the engine bay for about 10 minutes, that I think was from the serpentine belt. I wasn't driving, but my driver (my gf) called and I could certianly hear it on the phone. I could hear it in the cabin, then I could hear it from outside the car. She opened the hood and said it seemed to be coming from the passenger side down by the firewall, engine side. I could hear it while driving and while she was parked and idling.

I'm not familiar with the prius engine bay yet but that area is where the fan belt is i'm guessing if its like my other fwd cars.

It was cold out. She was driving about 55 mph. She had already driven 45 miles when it started. It continued to whine like that while parked and idling, and also while driving. She started and stopped the car and it would start when the car was started. I'm sure she had the heat on the whole time so i can't tell you if it quit when the engine cut out, but i bet it would have.

Then after about 10 minutes it stopped. It started a little bit at start up and then went away. She drove home 50 miles and didn't notice it anymore. I drove it last night in 12 degree city/suburban driving/ highway for 50 miles and never had it come back.

Anyone have any expereince with this? It was load. Like frighteningly loud. Loud like no customer will ever ride in your car if its happening. Only thing I could guess is its from a fan belt or one of the accessories, but almost all of the accessories are electrically driven right? I could buy some belt spray dressing and keep it in the trunk i suppose in case in happens again. I'm in the clear right now, but nervous about it randomly happening again with customers in the car.

This happened at the worst possible time. I lost a customer for a good airport taxi run that she had driven 50 miles to pick up. So sad. Customer rented a car instead of chancing breaking down on the way home on a 50 mile taxi ride in our prius.... and she won't need a ride back to the airport now!

 

Well that is some info i was fearing as i've heard the ac compressors are one of the weaker points of these rugged vehicles.

This guy has a broken MFD (new one is in the mail). So the ac compressor is running when the heat is on at all times I think? You either got ac with heat or you got nothing by toggling the on/off buton on the wheel is how it currently works.

I can read the screen but its cracked and you can't operate it. So you have to operate it from the steering wheel. Its either on or off and you can only adjust the temp up or down. Its also stuck in french which makes me feel green as well as multicultural!

(no we were not coming off any hills it was straight easy high way cruising, maybe a little stop and go, then blamo WHIIIIIIIIIIIIIIINE! is all that could be heard. And it was loaaaad and scary. ) I hate ac compressors. They are a home mechanics worst nightmare.

I'll pull the belt and check the bearings hopefully its not the ac compressor.

 

Yea it would be great if it was a fan, but at 15 degrees outside i doubt those are coming on.

So can anyone clear up info on how the heat/hvac works on these things. Its 15 degrees F out, i press 'on' on the steering wheel and the MFD says air conditiong on. Then I toggle the temp arrow up to MAX hot.

Is my ac compressor still running. And that is running off an independant motor right? If its something off the serpentine belt (which of course it may not be) it could only be from what wheels? The tensioner, dummy wheels, crank wheel, waterpump wheel, anything else?

 

Oh yea I want to add... The car is set at Defrost and can not be changed to floor or vent heat without a MFD replacement i think. Thats what the previous seller said.

So thats why i'm assuming the AC compressor is running when the heat is on for Dehumidification purposes.

Ok so you are telling me the radiator fans come on whenever the defrost is on?

The previous owner said she's been driving like this for a few years so I'm wondering if the car has been running the AC compressor and the fans A LOT more then normal. That could mean these are likely to fail sooner then cars with functioning MFD's....

It could not of been the tires cause this whinnig was screaming at her even when the car was parked and idling.

 

I have service records for breaks and things, but i don't have lifetime service records I'll look for them at the dealer.

 

Put a new MFD and is was EASY and its great to have.

The loud noise was coming back last night. First i hear a little rumbling for a few seconds which sounds like from the heat vents when I put the heat on, then a loud WHIIIIIIIIIIINE. Its frighteningly loud. I turn the heat off and it stops.

I toggle the heat on and off and it returns a few times. I give the heat a 5 minute break, turn it back on and it doesn't return for the final 15 miles of driving. So for now its a very intermitenant issue.

Is this likely the ac compressor going bad or the fans or waterpump? I have no clue. I have max heat selected and the ac/ is not on.

(the car is getting 40 to 52 mpg in sub freezing temp's right now)

 

THAT HAS TO BE WHAT IT IS!!!!! Great info.

It sounds like its coming from inside the car in the glovebox. Sweet!

Thanks patrick.