what's that servo noise 15 seconds after startup?

I think youre hearing the smog pump. It makes this noise a few seconds after startup and also right after shutting the engine off

 

A bit off topic but my neighbors M3's radiator fan stays on for a couple minutes after he's gotten out of the car! It pumps coolant and cools he engine for a while after he's stopped. He must really petal mash to the extreme

 

I'm so lucky....The voices inside my head drowned out all that noise!

 

I especially like the noise when I shut her off. She makes a coughing wheezing noise like an old model T or a chain smoker.

 

Its funny that I've never heard that sound before today, I changed the oil started it up and walked around the front and heard that weird servo sound.

 

I usually just say flaps down and my girlfriend gives me a look as I proceed down the road.

 

I also wonder this. If you ever find out what it is, please let me know. I know it's normal but curiosity always prevails

 

Nerco-Bump....I'm wondering about this sound too. I have it in my truck. My dad's truck doesn't have it......Go Figure?

 

It's the secondary air injection pump. It is a smog item that ONLY runs during startup and shutdown. It purges the exhaust fuels out of the exhaust on shutdown, and pushes clean air in during startup.

 

It’s that thing that you need to put the UNI filter on.

 

I've got a 2006 TRD OR V6 base....don't think I have that secondary air filter. I'd say it's coming from the ABS module or something in that area inside the cabin like an Hvac door opening but my A/C is out of commission and I didn't have the heater or blower on. ??? .... my truck has done it since I bought it a couple years ago. I recently wreck it and rebuilt it so, I was driving my dad's truck for almost a year. I don't think it's a major concern, I did some digging and found this thread. Thanks for the input.

 

The Secondary Air Injection System (equipped on all 2nd gen 4 cyl trucks and 2012+ V6 trucks) runs for 30-60 secs on a cold start and also for a few secs on shutdown on 13+ trucks (sounds sort of like a vacuum cleaner).

The ABS unit also runs a self check when the vehicle speed first exceeds 5 mph after startup (makes a quick couple of clicking sounds).

 

my 2009 make a woowoo noise when backing up first thing in morning.

its from the rear of the cab from what i can tell and only thing there is evap thing above the gas tank