Engine bay hum at cold start up

[billmc]

Last weekend I changed my oil, and afterwards now I hear a loud hum from the engine bay for about 30 seconds when I start it up in the mornings. It doesn't do it when the engine is started warm. I haven't been able to trace where it's coming from. Anybody recognize this?

Thanks,
Bill

 

[WaterGeo]

Does it sound like a loud shop vac? It sounds like the secondary air system (at least from what I have read). I'm currently paranoid about this happening on my rig as well.

 

[billmc]

yep, sounds like a shop vac. Why does it make you paranoid?

 

[WaterGeo]

I would recommend starting here (P1444/P1445 - Secondary Air Injection System) but maybe others can chime in as well. If it is the beginning of that system failing, you can fix it quickly and affordably with a bypass system (google "slyfox 75 bypass" or hewitt or rutech) for $50-$200. To fix it back to stock is a $2k-$3k fix.

 

[billmc]

Thanks, I'll read up on that