מכסה המנוע פתוח.

Literally, מכסה המנוע means the cover of the engine.

In everyday Hebrew, that is the normal way to say a car’s hood (British English: bonnet). So the sentence is naturally understood as The hood is open.

Because Hebrew usually leaves out the verb to be in the present tense.

So:

מכסה המנוע פתוח
= The hood is open

But in the past or future, Hebrew does use a form of to be:

• מכסה המנוע היה פתוח = The hood was open
• מכסה המנוע יהיה פתוח = The hood will be open

This is a construct chain (called smikhut), a very common Hebrew structure meaning X of Y.

So:

• מכסה המנוע = the engine’s cover / the hood

In a construct chain, the first noun usually does not take ה־, even when the whole phrase is definite. The definiteness comes from the second noun.

Compare:

• מכסה מנוע = an engine cover / a hood
• מכסה המנוע = the engine cover / the hood

Because פתוח here is a predicate adjective, not an adjective inside the noun phrase.

In this sentence:

מכסה המנוע פתוח
= The hood is open

Here, פתוח means is open, so it does not take ה־.

But if you wanted to say the open hood, then the adjective would be part of the noun phrase, and it would be definite:

מכסה המנוע הפתוח
= the open hood

So the difference is:

• מכסה המנוע פתוח = The hood is open
• מכסה המנוע הפתוח = the open hood

Because it agrees with מכסה, which is a masculine singular noun.

Hebrew adjectives must agree with the noun in gender and number.

So here:

• מכסה = masculine singular
• פתוח = masculine singular

For comparison:

• דלת פתוחה = an open door / the door is open
  (דלת is feminine singular, so פתוחה is feminine singular)

Here it is a noun: cover / lid / hood.

That is worth noticing because, in unpointed Hebrew, מכסה can also be read as a verb form meaning covers / is covering.

So without vowel marks, the spelling is the same, but the meaning comes from context.

Here the structure clearly shows it is the noun:

• מכסה המנוע = the hood
• פתוח = open

So the sentence is talking about a thing that is open, not about someone covering something.

Yes, that would be understandable and grammatical, and it would mean something like the cover of the engine is open.

But מכסה המנוע פתוח is more natural and idiomatic in Hebrew, especially for a car hood. Hebrew often prefers the construct form for tight, common combinations like this.

So:

• מכסה המנוע פתוח = more natural
• מכסה של המנוע פתוח = possible, but less standard here

To make it a question, you can either use intonation or add האם:

• מכסה המנוע פתוח? = Is the hood open?
• האם מכסה המנוע פתוח? = Is the hood open?

To make it negative:

• מכסה המנוע לא פתוח = The hood is not open

But in real speech, Hebrew often prefers the opposite adjective:

• מכסה המנוע סגור = The hood is closed