slapping sound

I have another question regarding my 2001 Caravan. Two or three times now I have heard when starting outsomewhere, a slapping sound that quickly goes away. It sort of sounds like a flat spot on a tire but that wouldn't go away within 200 or 300 feet (which it has). Can anyone give any sort of idea what it might be?
Many thanks, lansdowne

Front, back, left, right? Are you driving straight ahead or turning? Does applying the brakes change the noise? "Like a flatspot" = a rotating cyclic source = wheels, brakes, belts, pullies, cv joints...

Front, back, left, right? Are you driving straight ahead or turning? Does applying the brakes change the noise? "Like a flatspot" = a rotating cyclic source = wheels, brakes, belts, pullies, cv joints...

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I guess I wasn't precise as I might have been. It has happened three times to my knowledge.. when driving straight ahead and just after leaving my driveway after the vehicle has sat for a time. But it disappears by the time I have driven a short distance (like 200 or 300 feet). Seems like its comcing from the rear of the van (but sound DOES travel). Hard to explain exactly..but I've tried...
thanks
Lansdowne

It's the going away bit that throws me. Be nice if it was always there. It would be a hell of a lot easier to track down. Have someone sit in the back of the van and listen closely to pinpoint the noise. Noises are always hard to explain. You can't spell them.

I recently tracked a knock noise in the back of my van to a warped and loose plastic wheel well liner. Started 6 months ago and would come and go. I spent two weeks off and on crawling under the van looking for anything loose and found nothing. Then I decided to remove the rear shocks and check them out. As I was reinstalling them I noticed the well liner on the drivers side was cocked a little. Repostioned and secured it with rivets and haven't heard it since. In the process I got several good ideas from folkes on this forum. Turned out not to be the case but, gave me something to go on.

Possibilities: The well liners, spare tire, parking brake cable, rear seats, worn out rear window motors, sliding doors, exhaust pipes.

It's the going away bit that throws me. Be nice if it was always there. It would be a hell of a lot easier to track down. Have someone sit in the back of the van and listen closely to pinpoint the noise. Noises are always hard to explain. You can't spell them.

I recently tracked a knock noise in the back of my van to a warped and loose plastic wheel well liner. Started 6 months ago and would come and go. I spent two weeks off and on crawling under the van looking for anything loose and found nothing. Then I decided to remove the rear shocks and check them out. As I was reinstalling them I noticed the well liner on the drivers side was cocked a little. Repostioned and secured it with rivets and haven't heard it since. In the process I got several good ideas from folkes on this forum. Turned out not to be the case but, gave me something to go on.

Possibilities: The well liners, spare tire, parking brake cable, rear seats, worn out rear window motors, sliding doors, exhaust pipes.

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Thanks RIP.....I know sound can be hard to track down. Even harder for someone like me with just about zero mechanical knowledge or ability. You mentioned a few things I had not thought about.......I guess all one CAN do is wait it out and see if it gets worse. I have always been wary of sounds...possibly because of that limited knowledge...makes you a bit leery that it COULD be something serious. Probably not..hopefully not.
Thanks again....Lansdowne

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Thanks RIP.....I know sound can be hard to track down. Even harder for someone like me with just about zero mechanical knowledge or ability. You mentioned a few things I had not thought about.......I guess all one CAN do is wait it out and see if it gets worse. I have always been wary of sounds...possibly because of that limited knowledge...makes you a bit leery that it COULD be something serious. Probably not..hopefully not.
Thanks again....Lansdowne
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Further to previous notes..I have heard the sound at low speeds...could it possibly be something like a drive axle or shaft out of balance or something like that???
Lansdowne

At this point you can't rule anything out until you or someone else can get under the van and investigate. It will take time and patience but you'll nail it eventually.

Not going to say no on the out of balance axle but, not likely. If an axle was out of balance to the point it makes a noise, I would think it wouldn't go away. Are you feeling a vibration as well?

At this point you can't rule anything out until you or someone else can get under the van and investigate. It will take time and patience but you'll nail it eventually.

Not going to say no on the out of balance axle but, not likely. If an axle was out of balance to the point it makes a noise, I would think it wouldn't go away. Are you feeling a vibration as well?


Thanks again....possibly a very minor inference of vibration......such things drive me nuts..I always fear teh worset(real pessimest when vehicles are involved).
thanks again
Lansdowne