Loud whining noise when car first starts for about 3 minutes

[Meestahbig]

I have 2003 X5 6cyl. when I first start the car from cold, there is a loud whining/whirling noise for the first few minutes. Eventually, I can here this shut off and whatever is spinning slows down and the noise fades away. What is this... just so I know what to look out for. It's definitely different from the whistle I have at about 2k RPM, when its colder out. I think that is a crack somewhere in my vac intake line (throws the lean error code every 6 months or so)... I am going to fix that too.

[cn90]

How many miles?
And how old us the cooling system?
Search forum for cooling overhaul...

[Meestahbig]

143k miles. Cooling system is a mixed bag... I've replace the thermostat, the coolant and just last week replaced the expansion tank and the auto trans cool tstat (at the bottom of the expansion tank).

Is your question more about the coolant pump? Does this run for the first few minutes when the car is turned on? Belt driven?

[andrewwynn]

If it just plain stops (and the pounding in your head with it) almost surely the sap pump. My wife's has a bad bearing and it's a horrible howl.

I have foxwell scanner it can engage the pump to know for sure but you can confirm by putting your hand on the pump while you have somebody else start the car.

SAP on e53 M54 is painfully easy to find It's directly behind the right headlight and the filter for It is the most obvious thing above the right wheel well. Follow the intake hose from the filter to the air pump. It will be obvious.

[andrewwynn]

Look on YouTube there are videos to show how to refurbish the bearing as the pump is a pricey MFer. We've been dealing with the noise for a while but recently it started interfering with the efficiency of the airflow and throwing an occasional code so I'll have to move that repair up in the queue.


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[Meestahbig]

Yes, this noise just stops after 2 or 3 minutes (maybe less)... when you say the right wheel, is that sitting in the car or when looking at the car. Thank you.

[andrewwynn]

Right is right of the CAR not YOU. In nautical terms starboard. The SAP runs for about 90-120 seconds when engine is cold started.

[Meestahbig]

okay, got it... makes sense... LOL...

[Meestahbig]

yes, I know that funny looking contraption behind the right headlight. i have not had to mess with that yet!

[oldskewel]

From knowledge of other cars, but no problems yet in this area on my 2001 3.0i ...

the secondary air pump is designed to come on when the engine is stone cold (e.g., below about 60*F, so even a warm day can make it not needed), to pump extra air into the exhaust to complete combustion and bring the cat converters up to temp as quickly as possible. They run for a set time, like 60 or 90 seconds, then stop until the next stone cold start.

For cars that might not have these, sometimes you might detect a faint gas smell coming from the exhaust immediately following a cold start. That's what the SAP is intended to mitigate.

So it's an emissions optimization thing that only even tries to matter in the first minute or so of a cold start.

If it were me, I'd surely track it down to confirm where the unknown noise was coming from, but if I found it to be the secondary air pump / air pump / smog pump ... just between you and me ... I might not make it a top priority to fix it.