My 2007 HHR as recently started having a howl as I go through the gears (5 speed manual), but stops after just a moment or so, and also does it even if the clutch is engaged as long as I push on the accelerator. As noted I do not hear it when driving after a minute or so, If I stop at an intersection and take off after driving for a bit I normally don't hear it, but if the engine is left to sit for a few minutes (like to fill up for gas, which it did today), then it will make the noise again.

SteveT.

 

Flex pipe, if it does it even if parked and pusshing pedal. Wheel hubs if only while moving.
A cracke flex pipe can be deadly.

 

I will have it checked, but it does not sound like an exhaust leak, it really sounds like a bearing, but the engine runs fine and no vibration.. As noted, once I have driven for a couple of minutes it goes away. Also, when I pull into my garage, (with the garage door open of course) I hear no exhaust leak.

SteveT.

 

So it never does it unless the car is moving, never at idle or when revving standing still? Does the pitch or volume vary with speed? Please confirm/clarify.

Maybe post a vid? (For the sound, of course.)

 

I’m thinking wheel hubs.

 

Not wheel hubs when it does it when sitting still with the transmission in neutral and foot off the clutch. Besides, the hub bearing have been replaced both front and rear.

Funny thing is it is intermittent as to how loud it is. Yesterday at one point, it was quite loud, today, no where near as loud.

SteveT.

 

it does not do it at idle, but yes will do it in neutral sitting still with my foot off the clutch when I rev it up, like today, it barely did it at all, not the loud howl.

SteveT.

 

I do not think it is the flex pipe, as it would not be as intermittent as it seems to be, but, I have set up an appointment to have it checked out tomorrow.

SteveT.

 

The other option is the air cleaner bracket is broken and rattling.

 

Not a rattle. I know that one, as I already replaced the bracket.

SteveT.