We just purchased a Nissan Altima and wondered what the purpose of the HUGE plastic cover over most of the engine is. Is it just there to make things for marketing? I would love to remove it so that I can keep an eye on what is going on in the engine room, but didn’t want to cause trouble if there was a real purpose for it.
I’ve often wondered this myself, and I think its only useful purpose (if you can call it that) is to minimize confusion whenever a novice looks under the hood. The dipstick and oil fill cap tend to be about the only things NOT covered, and so they’re easy to find.
I suppose it could also have some function in noise dampening, but I don’t think you’d be hurting anything if you took it off.
Well, if you remove that cover, you’ll find it does such things as protects the fuel injector connectors and all the other electrical connectors for the engine mangement system. I thought the same thing at one time, 'til you look at all the electrical crap on top of an engine today.
Tester
What is it protecting the electrical stuff from? I always thought that heat was the enemy of electronics, and that cover must be keeping things hot under there…
The other thing it contains is a sound insulation layer. Take it off and you’ll hear your engine’s valvetrain a more clearly.
I can’t count the times that a fuel injector got cracked because an old mechanic’s dentures fell on it. That plastic must be there to provide a plastic sheet that you can patch the bumper with if you hit something. We’ll start calling it The Flying Nun (age 50+).
I consider it sound insulation, mostly.
From moisture such as from a heavy rain or fog. The ideal situation would be if these electrical components could be put into a control box. Since they can’t do that, that shroud is the next best thing.
Tester
My son pulled his off is 06 Spec-V (Altima engine) when new. Hasn’t been a problem. The connector that has the biggest problem with rain is the rear O2 sensor connector, it fill up with water all the time and sets the code for catalytic converter efficiency. That connector is at the bottom of the engine and isn’t protected by the cover.
Just an example!
Tester
Makes for a clean looking engine compartment at the least. They usually are not so hard to get off to service the components underneath.
You must be from a time period where it was a good idea to make a underhood inspection every 100 miles.
Probably no problem, besides noise, but don’t count on liking to look at what you find. It might be a messy jumble of hoses and wires. Wish they didn’t use those covers, instead they should make the engine look good like this Audi Q7:
http://z.about.com/d/trucks/1/0/u/Z/audi_q7_4171.jpg
You are so right! It looks like the Flying Nun’s habit. (Habit = Nun hat for those not blessed enough to be raised in the Catholic school system.)
You betcha…our family had VW’s. (1975 bus and first generation Rabbit) You were lucky to go 100 miles without some sort of disaster in spite of loving care. You can’t kill a VW unless you run it out of oil, but a VW is always on death’s doorstep…even when brand new.
My wife’s 2005 Legacy GT has one. Two of the four plastic screws that hold it down(Subaru cheaped out) are missing. So it actually vibrates a little and makes noise 
I believe they broke them when they replaced the belts a while back.
I believe on her car it directs the air flow to her top mounted (turbo) inter-cooler.
No no no no no, Texases. An engine that looks good has chrome valvecovers, braided wire covers, a high-rise manifold, and a quad or two. The headers are painted in high-temp paint in a nice color that complements the block. And everything is in full view.
This Q7 is like a kitchen cupboard where everything is hidden so it looks neat and organized but it’s impossible to find the peanut butter without emptying out the cupboard!
Yes, nothing better than a dressed-up V8, but those days are gone. On the Audi, at least you can see the valve covers, the intake manifold, ect, instead of a big black piece of plastic. We now have the best technology ever in our engines, and it’s almost always completely hidden! Same beef with sportbikes. If I can’t see the motor, I’m not interested.
I just can’t seem to accept the 21st century…