I have developed an annoying rattle since the car had a bit of a hard knock a few weeks ago. I have spent a lot of time trying to trace it. It is a medium-frequency sound (a heat shield rattle is high frequency, for example) that echoes the engine speed especially around 2500 RPM regardless of whether the vehicle is moving. It is audible from inside the car much more than from the engine compartment and seems to be located (oh dread words) at the heater core.

Motor mounts and tranny mounts are recent and I have not been able to find any contact between drivetrain and body. I have not been able to reach any part (kick panels removed) which affects the rattle even a small amount.

Has anyone had this problem and dealt with it? Sure dont want to go down to the heater core if I don't have to.

By the way, there is a piece of cast iron bolted to the firewall (engine side) just about exactly where the heater core must be on the inside. Looks like a vibration dampening device. Anyone know what it is bolted to? The bolts will turn with medium resistance and do not tighten; must be locknuts on the inside. Under the heater core no doubt. Applying pressure to this device does not affect the rattle, however.

THIS IS TOO NICE A CAR TO RATTLE!

Chris