yet another stupid question
 

I had assumed that the plastic pop off cover directly behind my engine was the battery. Then I discovered the battery cleverly hidden on the passenger side of the trunk. Anybody had to replace that 30 foot cable?
So what is lurking beneath the cover behind the engine?
Thanks

There are no stupid questions! Just stupid PEOPLE!
 

Take it off and see! The center (separate) cover is the charcoal odor/pollen filter for the AC; under the one(s) you're asking about are ECU, the heater valves and alarm horn on the left, brake booster on right... You would be wise to shop-vac and blow out any leaves composting in there.

The gasket at the front of the cover just pulls off; then press each side inward until the tabs clear their slots in the fenders. Then sort of downward and forward and viola! Note they fit into the gasket toward the windshield edge.

-Tom

Under the plenum cover...
 

It's called the plenum cover.

Basically, you have the HVAC filter right in the center, and then the heater control valve and some related water hoses on one side along with the engine computer box(es) [ECU--multiple on a V10 or W12], and various electrical stuff and the brake master cylinder on the other. The coolant bottle is also back there (at least for a W12), and also the filler spout for the windshield wiper fluid, though the wiper bottle itself is further below in the upper fender area. Some of this will vary depending on the motor, and the master cylinder (and I think heater valve, electrical and ECU) switches sides depending on left or right hand drive. There is also a nice front shock tower tie bar set up that integrates closely with the body work in the same area if you look closely.

The covers most commonly come off to get to the heater bleed screws, and maybe to get the HVAC filter cover to fit correctly. Very important to get the leaf debris out of there periodically too--easiest with an air pressure hose or vacuum--in order to avoid interior water issues.

another stupid question.
 

You guys kill me. Thanks