2003 Toyota 4Runner Underbody rattling noise

CAMI171

MEMBER
2003 TOYOTA 4RUNNER
6 CYL
4WD
AUTOMATIC
83,100 MILES

Hi-My 4runner recently started making a rattling noise when I accelerate from stand still/near stand still. I first noticed it when I had it engaged in 4Hi but it actually happens also in 2wd. The noise comes from the underbody, it seems like on the driver's side (somewhere between the driver and passenger seats). Happens a lot when I accelerate after sitting at a red light. It's really loud right away and I can feel vibrations (sounds like metal on metal) but seems to disappear once I get to 40mph and up. But in stop and go traffic it comes back every time I accelerate back up.

1 Reply

MATHIASO

MECHANIC
1,209 POSTS

Hello cami171

check for loose heat shields around the catalytic converter or exhaust pipes clamps.
Rust often weakens the spot welds that hold the heat shields to the exhaust system.
When the weld fails, the shield comes loose just enough to vibrate and produce a rattle or buzz that reverberates throughout the entire vehicle. The noise may only be heard at certain engine rpm or when decelerating when harmonic vibrations shake the exhaust system at a resonant frequency.
Use a medium-sized screwdriver to check the shields for looseness. Gently pry between the shield and converter or pipe to see if any of the spot welds or mounting flanges have failed. Loose heat shields can be secured by rewelding, or by installing clamps. If a shield is damaged or badly rusted, replacement is recommended.