Loud whirring noise


#1

The ‘search’ link on this forum is nothing short of a bad joke. I typed in "A/C problems’ and get 7 pages X 50 posts and out of all that…one that actually refers to an A/c fault.



Rant over.



Vehicle in question: 2003 Pontiac Montana 3.4L V6 with about 87k miles on it.



Here’s the problem, when driving at about 25 mph or more a loud whirring noise starts and continues until you back off the throttle and the rpms drop below 1k.



Once below 1k the noise stops until you speed up and it starts all over again.



Now, this is with the A/C off.



It sounds to me as though the A/C fans kick in during that time (but A/C is off, fan switch off, a/c switch off)



When you turn the A/C on, turn the fan switch on, you get lots of cold air from the vents.



Here’s the real problem: when you have driven for some time (like an hour or more) with the A/C working, the engine light comes on (Canada) and flashes a couple of times then stays on solid until the A/C is turned off.

Shortly after, the engine light turns off and stays off.



There is another fault that pops up then too.

The engine has an acceleration hesitation during the time the engine light is on.



This is my daughters van and I know you all will say to have the stored code(s) read first, I told her I’d post here and see if you guys had some thoughts on the loud whirring noise.



I heard this noise along with and over the normal engine noise.


#2

Any ideas?


#3

Post the codes first?


#4

That’s what I thought. Okay then. I’ll have to wait for the daughter to get time between working hours to get them.


#5

I’m going to guess that your AC compressors bearings are failing and when running for a period they overheat, bind up, and load down the crankshaft…badly. When you turn the AC off and the AC compressor clutch disengages the load disappears from the crankshaft and everything engine-wise goes back to normal.

Let us know what you ultimately find out.


#6

Thanks for your input Mb, it’s appreciated.

Wouldn’t there be worn bearing noises in this instance? When the A/C is running I don’t hear nay screeching or grinding sounds.

The load on the crankshaft is what contributes to the hesitation upon acceleration then?

So, in short, if the A/C is left OFF until some repair is made no damage should be done.

I haven’t heard from our daughter yet so I’ll have to wait for a code and go from there.

With my luck the code will read something like: misfiring and A/C kaput.


#7

I’m basing this guess on:

“when you have driven for some time (like an hour or more) with the A/C working, the engine light comes on (Canada) and flashes a couple of times then stays on solid until the A/C is turned off. Shortly after, the engine light turns off and stays off.”

Yeah, it’s my guess that the load on the crankshaft causes this. The crank is the best place to get direct power, but it’s also the most susceptable to “feeling it” if it’s loaded down. It’s a direct link both ways.

Correct, if the AC is kept off no damage should be done. It sounds from the post like as long as the clutch is disengaged the pulley is free to spin, like the bad bearings are in the compressor itself.


#8

Mb, talked with the daughter tonight and she says the shop (that our son and her have used before with success) tech said the bearings are worn and need changing.

Here’s the kicker, when I asked which bearings she just repeats what she previously said.

MY question is as long as the compressor bearings aren’t seized will the A/C continue to operate properly? It works fine right now.

Whatever the outcome, she’s taking the van in on Monday to have the work done to the tune of $300.

Hopefully the loud noise and the hesitation run hand in hand.

I’ll post here again after I see the work order and the results of the aforementioned repair.


#9

Update: Loud ‘whirring’ noise turned out to be a worn right front wheel bearing.

Noise was vehicle speed related where the noise didn’t occur until 30mph and continued on up until you slowed below that speed.

I’ve heard wheel bearings going before, but they didn’t sound (to me) like this one.

The daughter said the mechanic (independent shop) who test drove the van id the noise immediately.

Noise is gone and while using the A/C there is no CEL on. Can’t figure that one out. Nothing to do with worn wheel bearings (replacement). Seems a little strange.

As long as she’s happy, I’m happy.

Thanks again for your input.