Intermittent rattle underneath the rear of my car

MECHYUDA

MEMBER
HONDA CIVIC

2004 Honda Civic EX Coupe (auto)
Original owner with warranty still active

During the winter of 2005, when my car gets really cold, twice I noticed a rattling sound when I shut my doors or trunk coming underneath my car toward the rear. The rattle is not a sharp metallic sound. The rattle suddenly occurs and almost abruptly dies down -- no fading away.

When I drive the car or let it warm up, the rattle disappears. Which is really frustrating because everyime I drive to the dealership, I will not be able to recreate the sound. The dealership mechanics want to take apart parts under my car and probe around. I want to keep this as my last option.

I crawled under the car when it's cool and carefully knocked parts around with my hand to recreate the sound. Sometimes I could recreate it, sometimes I can't. I cannot fully fit under my car (I have no jack stands), so all I could tell is that the sound seems to come from between the rear axle and muffler.

Seeing how heat gets rid of the rattle, I am guessing that a baffle or internal part of the exhaust system is loose. Another possibility is some obscure suspension component that is loose, but expands and tightens up when my car warms up.

Does anyone have any similar experiences, solutions, and/or advice concerning this issue? Is this issue normal and ignoreable?

1 Reply

PALCO

MEMBER
83 POSTS

Ok I don't know the 2004 model but. Your car cabin has exit air vents. Useualy in the trunk area and/or in the rear door jams. That may lead to the trunk area. When you close a door or lid on these newer cars they are tightly sealed. You create a rush of air creating pressure. These cabin vents are made of a soft rubber flaps. When its cold out the outside of these vents are exposed to the out side. And they can outright harden up and sound like a barn door flapping in the wind. Thats my experiance one winter in billings mt. Good luck