What is the cover that covers the engine?
The cover that sits over the engine is typically called the engine cover. The exterior lid that you see from outside the car is the hood (also known as the bonnet in some regions). The top surface that sits directly on the engine’s cylinder heads is called the valve cover (sometimes referred to as a rocker cover).
In automotive terminology, several different parts shield or access the engine, and their names vary by function and location. This article explains the common covers you’ll encounter in a typical car’s engine bay and how they differ.
Key engine covers and what they do
Before exploring each type, here is a quick overview of the main covers you’re likely to encounter in most passenger cars.
Engine cover (or top engine cover): A decorative or functional panel that sits on top of the engine block. It’s usually made of plastic or composite material and is aimed at reducing engine noise, protecting components, and improving aesthetics. Not every engine has a visible engine cover, and its exact look can vary by make and model.
Valve cover (also called rocker cover): A metal or plastic cover that sits directly on top of the engine’s cylinder head(s). It seals the opening for the valve train and houses components such as the oil filler cap and PCV breather. There is typically one valve cover per cylinder bank (one long cover for inline engines; two for many V-shaped engines).
Hood (or bonnet): The exterior cover of the engine bay—the metal or composite lid you open with a latch or handle. It protects the engine from the elements and provides access for maintenance when raised. The hood is not part of the engine itself, but it covers it from above.
All three terms describe protective or access features around the engine, but they operate in different contexts: the engine cover is inside the bay, the valve cover is the top-most seal on the engine, and the hood is the external shell that covers the whole engine compartment.
Valve cover vs engine cover: how the terms relate
The valve cover is a specific engine component that sits atop the cylinder heads, sealing the valve train and containing oil. By contrast, an engine cover is a broader, often cosmetic panel that covers the upper portion of the engine for noise reduction and aesthetics. Some engines have both: a visible engine cover inside the bay, and a valve cover beneath it. The hood, meanwhile, sits outside the engine and opens to give you access for maintenance.
Where these parts sit on a typical car
Understanding their placement helps distinguish them in everyday use and maintenance.
: Located on top of the engine block, toward the center of the engine bay. It is the panel you may see or remove if you’re curious about the layout of the components beneath.
Valve cover: Mounted directly above the cylinder head(s) at the very top edge of the engine. It’s usually visible when you peek into the engine bay, especially around the intake/exhaust side of the engine.
Hood: The large exterior shell that forms the top of the car’s body. It’s hinged at the back and opens upward to reveal the engine bay for service.
In practice, the exact appearance and naming can vary by vehicle make, model, and region, but the fundamental distinctions remain the same: inside covers (engine/valve) versus the external hood.
Maintenance and practical tips
Knowing which cover is which can help with basic maintenance and leak checks.
- Check around the valve cover gasket for oil leaks, especially where the valve cover meets the cylinder head.
- When removing or reinstalling an engine cover, follow manufacturer guidance to avoid damaging fasteners or the cover itself.
- Realize that some engines hide the valve cover beneath an engine cover; removing the exterior cover may be necessary to access the valve cover for service.
These practices help ensure the engine remains properly sealed and quiet, while keeping the engine bay-looking neat and organized.
In other machines and contexts
Different machines use similar concepts. Motorcycles, lawnmowers, and industrial engines have valve covers over the cylinder heads and may feature engine covers for noise reduction. Agricultural and industrial equipment often emphasizes protective enclosures around the engine for durability and safety, even when a separate hood is not used.
Summary: The cover that covers the engine has two commonly used names depending on context. The internal, top-of-engine cover is the engine cover, while the top-most seal directly over the engine’s moving parts is the valve cover. The exterior lid you open to access the engine is the hood (bonnet). Together, these parts protect, insulate, and provide access to the engine for maintenance and operation.
