Rob, there is an odd noise coming from my Caravan lately. At first, it only came once per driving session, at around 40-50 km, but has increased its frequency while driving at regular speeds of 100 km. I'll list a series of information bits.
The sound is very brief, and if you were to say the word "grrr" quickly, it would be about that - a second or so in length. It's difficult to describe the sound, but it sounds like (1) an air compressor on a rig when it shuts off - "phfffft", or (2) if your engine is running and you unintentionally engage the starter again, that specific grating sound of the bendix trying to make things happen, or a combination of those two things.
It has never affected performance. There is no bump, lurch, slowdown, speedup, or anything that would indicate a mechanical area to investigate. I've ruled out the door-lock motors that happen at around 30-40 km per hour since it has happened before the car even moves.
Having ruled out practically everything - engine, tranny, and computer related things while in motion, the best hypothesis is that the starter is acting up. Could the bendix be getting weak? Could a silly-noid be getting para-noid and coming on-line when it shouldn't?
Best regards, Eric
Love your command of illustrating mechanical sounds as well as technical terms - I wish I had said these first.
Great question Eric and I think I have an answer - albeit weird.
I think you have a noisy roof rack.
My friends at Alldata.com tell me that Dodge had a technical service bulletin (23-14-98) that addresses all sorts of odd-ball noises like the ones you have so adeptly described. The bulletin could not actually pin down the sound variations other than to say the owner could experience a variety of sounds that ranged from mechanical grinding to animal sounds!
The bulletin outlines the replacement of cross rails with an updated version.
The original ones vibrated because they did not have enough wind resistance strength. Assuming you have factory-installed racks, this explains the weird and wonderful noises you've been hearing. A trip to your Dodge parts department will be next on your honey-do list. Cross rails come in colours to match your van.
Give this a try Eric, because I can't find anything else in my research that even comes close to describing the reluctance your Caravan has to moving down the highway without sounding like the special effects department of an action movie.
Electric Mini left this driver drained