[Vet4jdc]

For the last month I have been hearing a "revving" noise from the engine...but it's not the motor rpm's and not a speed increase. At a normal 30-50 mph it will sound normal and then with no acceleration, I hear the revving, turbo boost gauge does not change and rpm's does not change. The revving sound may go on for a few seconds or up to 15 seconds and then stop? Ford says they can't detect anything wrong when it was in the shop. The more I read here I am thinking its the fan cutting in and out? It didn't do this when it was hot (summer)...why start now? Any ideas?

 

[frdfan]

I have the same thing going on. I turns out it is the fan coming on and off. The new flash changed a bunch of stuff and this was one of them. Fan comes on and off to keep temp more even. Annoying but harmless.

 

[amb82]

Mine truck did this for the first few weeks I had the truck but once I installed a tuner and fixed leaks on both upper and lower radiator hoses it doesnt anymore. weird! It sounded like the fan was getting ready to take off out of the engine compartment. It was the middle of the summer but it would cycle in the mornings too before it reached 90 degrees outside.