Thanks everyone. I'll get the manifold sorted out regardless.
I'm still scratching my head about how to test the fan clutch idea (I live in Monterey...it is *always* cloudy and cool!), but the curious thing is that I've had the RV for almost a year and this is the first time the noise has occurred.
I agree that the 2 second delay makes the manifold idea problematic, and I still don't see why it would only happen under load. I picked up a tach to see if there is any RPM change associated with the noise. Would have an answer for you all already but learned this morning that the coil has a fancy plug rather than screw-on terminals!
Best,
Jim
