Common and relatively minor causes:
* Loose items in the trunk: The most common cause. Check for anything that's shifted and is now banging around – spare tire, tools, groceries, etc.
* Exhaust system: A loose heat shield or a slightly loose component in the exhaust system can rattle, especially when the engine is running. This can be a safety concern if it gets worse.
* Suspension components: Worn bushings or loose components in the suspension (shocks, struts, sway bar links) can create rattles, particularly over bumps.
* Loose trim pieces: Plastic panels or trim pieces in the rear of the car can come loose and rattle.
* Spare tire: If the spare is loose or the retaining mechanism is faulty, it may rattle.
More serious (potentially) causes:
* Brake components: While less common, a loose or worn brake component (caliper, shield, etc.) can sometimes rattle. This is something that should be checked immediately.
* Differential problems: A problem with the differential (the part that manages power distribution to the rear wheels) can cause a rumbling or rattling noise, usually more noticeable at low speeds or when turning. This is a serious issue.
* Tail light or other body panel: A loose tail light or other body panel can rattle against its mounting points.
Troubleshooting steps:
1. Check the trunk: This is the easiest and most likely place to find the source of the rattle.
2. Drive over different road surfaces: This helps pinpoint if the rattle is related to suspension or something else.
3. Listen carefully: Try to pinpoint the location of the rattle. Is it constant or only when going over bumps? Does it change with engine speed?
4. Have someone ride in the back: Having a passenger listen from the rear seat can sometimes help pinpoint the location.
If you can't easily identify and fix the problem yourself, it's best to take your car to a mechanic. Ignoring a rattle, especially one that seems to be getting worse, could lead to more significant and costly repairs down the line. A brake or differential problem, for example, are serious safety concerns.
