Blowing/thrum thrum noise from engine on startup for 10 secs

[soupytwister]

Looked at a 53-reg/2004 XC90 D5SE tonight.
On startup, there seems to be a sort of thrum-thrum blowy type noise coming from the engine which lasts around 10 seconds and then disappears instantly - ie, something pump/aircon/electrical related???

Couldn't isolate where coming from but seemed more on right side of engine (looking from front of car).

Searched on google, but can't really find anything it might be.

Any ideas? or is this normal? I've looked at a few, and I'm sure I would have noticed it on others.

[400-ascona]

If it was next to the headlight it may be the vacuum pump?

[soupytwister]

Thanks. The vacuum pump for what?
Any idea what the issue would be with it? ie, about to expire or needing adjusment/replaced?

If it was next to the headlight it may be the vacuum pump?

[BestGear]

Thanks. The vacuum pump for what?
Any idea what the issue would be with it? ie, about to expire or needing adjusment/replaced?

Some vehicles (of any marque) blow air into the exhaust so that it helps heat up the CATS quicker at startup.

I am assuming this is the pump to do that...

D

[soupytwister]

OK, thanks. Sounds feasible.

It's just not something I've noticed in other XC90's I've been looking at, but then when I looked at others, it wasn't such cold weather.....not sure if it's temp related and would blow more air in cold weather to warm it up :)

[soupytwister]

My wife also thought this XC90 sounded a bit more burbly than normal when it turned up. I guess given the above, it could indicate a manifold or exhaust issue - and hence why this startup sound also is more noticeable....

[XC90 Dave]

This type of noise is usually produced by the cooling fan when the engine is cold, which after a short time disengages through the viscous coupling. It would be worth starting the engine with the bonnet open and seeing if this is the case.

[RoyMacDonald]

This type of noise is usually produced by the cooling fan when the engine is cold, which after a short time disengages through the viscous coupling. It would be worth starting the engine with the bonnet open and seeing if this is the case.

The XC90 has a temp controled huge electric fan. I've never seen mine run.

[400-ascona]

The vacuum pump supplements the servo for brakes. The cooling fan shouldn't be turning.