Curious...what is that shut-down sound

I notice that when I shut the engine down (2.7L) that there is "something" that seems to spool down, maybe a fraction of a second longer than the engine itself. I have no idea what that is...is there some kind of pump that is spinning down? I'm sure everything is in order, just curious what that sound is whenever I turn the engine off.

 

Secondary air injection pump more than likely

 

It maybe the " secondary air pump " that feeds air into the exhaust manifold for some EPA nonsense etc..as it's a squirrel cage blower design..can't say for sure if that's what you hear but it's a possibility..it's located on the passenger side next to the radiator

 

Thanks...that makes sense. And it does seem to come from the front passenger side. Since my wife doesn't drive the truck I've never been under the hood during shut-down.

 

And by the way, I have not fed or serviced the bunny....and I didn't see that in the maintenance schedule. Any advice is welcomed.

 

These systems are considered "maintenance free" by Toyota but there is 1 potential issue that I know of... remove the center screw (torx), remove the cover and check the little foam air filter block. These are known to disintegrate and damage the air pump and/or air injection valve on the exhaust manifold. Some people remove the foam and add a little UNI filter on the intake side of the cover. I did this and my local smog tech nearly flagged this as emissions non-compliant until we talked about it and he approved the mod. Now when smog is due, I remove the UNI filter and replace the original plastic cap thingy, get the smog check done, then put the UNI filter back on. Maybe others will chime in on this delightful little foam air filter block.

 

I'm having a noise also from the same area except it's not a spool down its more of a "POP". Kind of like pulling on an inflated balloon and letting it go. No CEL's but I am wondering if this thing is going bad? There is a company that makes a delete/override kit for it, wondering if it may be worth the $$$ to just eliminate it.

Cheers,

Doc