Vacuum noise or ? 1994 Ford 460 28 ft Bounder

[tickermarie]

Our motorhome started making this awful noise shortly after we bought it and we have no clue as to what it might be. Most of the time it doesn't happen til we have been driving it over an hour or so. I posted a video with sound on youtube so you could hear it. Help, it is really loud when you are inside, even happens when you are at a complete stop!
https://www.youtube.com/watch?v=T3EFO3fUYr0 If anyone has a clue we would appreciate your input.
Thanks

[Carm]

Sounds pretty much like the Idle Air Control, mine was making a similar sound once in a while, took me about 2 years to figure it out. It wouldn't do it while accelerating but would do it under steady throttle, decelerating and idling. If you're handy with tools it's an easy fix. The IAC is under the 2 big hoses that go into the throttle body: it's a quick and easy replacement.

[tickermarie]

Well, the loose hose clamp wasn't the problem. Went to Ford garage and had them listen to the video I took and their mechanic thinks it is the idle air control valve so we purchased one and have yet to take it for a drive and see if it has fixed the problem. Also mentioned a resonator chamber, but they are no longer available. We usually have to drive our motor home over an hour before it starts making a noise. Will let you know.

[tickermarie]

Doesn't have electric vacuum pump and he doesn't think it has anything to do with the EGR. He just told me he found a hose that was disconnected and a loose hose clamp on another hose. He connected the one and tighted up the hose clamp on the other! Thinks that maybe when we had the exhuast manifold fixed they forgot to reconnect/tighten? Hopefully this will solve the problem. If it doesn't I will let you know. Thanks for the input.

[enblethen]

What type of EGR system is on your unit?

[ScottG]

It kinda sounds like a loud electric vacuum pump but I'm not sure any 460 ever had one.
They're more common on diesels.

[tickermarie]

No, it does not have an electric fan. It only does it under deceleration, not acceleration. It only does it for a few seconds after we stop, doesn't matter if it is in gear or not.

[weasel4]

I agree, not engine or drive train induced. Any generator or electrical running while driving?

[MountainAir05]

Also check the intake for nest and clog filter.

[enblethen]

A vacuum leak would change with engine RPMs and whether it is accelerating or slowing down.
Sounds like it is pretty constant.
Is there an electric fan on the radiator?