Exhaust System:
* Loose heat shields: These are thin metal shields that protect components from exhaust heat. They often rattle due to age, vibration, or loose mounting bolts. This is a common and relatively easy fix.
* Loose or damaged muffler/exhaust pipe: A rusted-through or poorly connected part of the exhaust system will rattle when the engine vibrates under acceleration.
* Exhaust hangers: These are the rubber or metal mounts that hold the exhaust system in place. Worn or broken hangers will allow the exhaust to move and rattle.
Engine Components:
* Loose components: Something inside the engine bay might be loose and rattling against other parts. This could be anything from a loose bracket to a poorly secured accessory. This is harder to diagnose without a visual inspection.
* Catalytic converter: A failing catalytic converter can rattle due to internal damage. This is a more serious issue and often requires replacement.
* Heat shield on catalytic converter: Similar to the exhaust heat shield, this can also rattle.
Drivetrain:
* U-joints (universal joints): These connect the driveshaft and can wear out, causing a clicking or rattling noise, especially under acceleration.
* Driveshaft: A bent or damaged driveshaft can also create a rattling sound.
* Differential: Problems within the differential can cause noises under load (acceleration). This is less likely to be just a rattle.
Other Possibilities:
* Loose items in the cargo area: Something as simple as a loose tool or spare tire could be rattling.
Troubleshooting Steps:
1. Listen carefully: Try to pinpoint the location of the rattle. Is it coming from the front, rear, or under the vehicle? Does the noise change with engine speed or only under acceleration?
2. Visual Inspection: Look under the vehicle for loose or damaged exhaust components. Check for anything loose in the engine bay or cargo area.
3. Road Test: Have someone listen while you accelerate to help pinpoint the source of the noise.
4. Shake things: Gently shake components in the engine bay (with the engine off) to see if you can identify anything loose.
If you're not comfortable performing these checks yourself, take your Explorer to a mechanic for diagnosis and repair. Ignoring a rattling noise could lead to more serious and expensive problems down the road.
