Recently I have noticed a loud noise that usually starts and last say 15 seconds, then dies. I always assumed it was the radiator fan running. As the noise sometimes started as soon as the car started, I began to suspect something was up. It's winter and the engine is darn cold. So this morning I raised the hood before starting the car. It did not start making the noise right away but did after the car began to warm up. It doesn't appear to be the coolant fan. The fan was not turning and the noise seemed to be coming from the area under the battery. Is there something down there and is it something I need to be concerned about? When it is running, it sounds like a jet engine and seems to shut down the same way. Not quickly but like an electric motor drifting to a stop. Thanks for any help or ideas.

That car has an air pump that blows air into exhaust starting 10 seconds after a cold start and ending approximately one minute after that.

The pump is in the area below battery.

It would seem you have a noisey pump.

The noise from this pump should be similar to one of those plug in the cig lighter car vacuums but maybe a little quieter.

Thanks for the info. I've noticed that this pump will also come on and run for 10 to 15 seconds at a time after the car has started warming up. It's loud enough that you can easily hear it in the car with the radio playing. Does this mean a bad bearing? Will it cause more problems if we keep on driving? What happens if it quits? WE never noticed it before this winter. Does it not run in the summer with a cold engine? And we didn't notice it last winter. I would guess that would mean it's headed toward breaking down. Do you know if it's covered under warranty? Or is this noise acceptable by Volvo? What's the purpose of blowing in the cold air? to keep the exhaust emissions down when the fuel ratio is higher?

Sorry for all the questions, always curious I guess. Thanks again.

The air pump is an emmission item. It pumps air into your exhaust during warmup to help get the catalytic converter hotter faster, thus reducing emissions. The problem is that this pump gets waterlogged due to a design flaw in a valve that lets in moisture laden air. When it gets real cold outside, the fan vanes in the pump freeze up and break, eventually resulting in a check engine light. The fix is a new pump (it's electrically operated) and a new redesigned valve. Mine went last winter and was replaced under warranty. If yours is making all this racket, I'd bring it to the atention of the service guys and see if it needs to be replaced now, under warranty. I bet there is ice in it or a broken fan already.

Doug

Thanks for the info.

TL