La mecánica abrió el capó porque el coche hacía un ruido raro.

In this sentence, la mecánica means the female mechanic.

Spanish often uses the same word for a profession in both adjective and noun use:

• mecánico = male mechanic
• mecánica = female mechanic

So:

• El mecánico abrió el capó = The male mechanic opened the bonnet/hood.
• La mecánica abrió el capó = The female mechanic opened the bonnet/hood.

Be careful: la mecánica can also mean mechanics as a field or subject, depending on context. But here, because it is followed by an action a person does (abrió el capó), it clearly means the female mechanic.

Abrió is the preterite, which is used for a completed action in the past.

• abrió = opened

Here, opening the bonnet/hood is seen as one finished event:

• La mecánica abrió el capó = The mechanic opened the bonnet/hood.

If you used abría, it would sound more like was opening or used to open, which does not fit the idea as well here.

This sentence contrasts two past ideas:

• abrió = the main completed action
• hacía = the background ongoing situation

That contrast is very common in Spanish.

Hacía is the imperfect, used here for a background or ongoing situation in the past.

The car’s strange noise was not a single completed event; it was an ongoing condition or repeated sound in the background. So Spanish uses the imperfect:

• hacía un ruido raro = was making a strange noise / made a strange noise

In natural English, you might translate it as:

• because the car was making a strange noise

So the pattern is:

• preterite for the completed action: abrió
• imperfect for the background situation: hacía

Spanish commonly uses hacer with nouns to express things that English often expresses with a simple verb phrase.

So:

• hacer un ruido = to make a noise
• hacer un sonido = to make a sound

This is a very normal structure in Spanish. In this sentence:

• el coche hacía un ruido raro = the car was making a strange noise

It may feel more word-for-word than English, but it is standard Spanish.

Capó means the hood of a car in American English, or the bonnet in British English.

In Spain, capó is the normal word, so this sentence fits Peninsular Spanish well.

In other Spanish-speaking regions, you may also hear different words, such as:

• cofre in some parts of Latin America

So if you are learning Spanish from Spain, capó is the form you should remember.

These are different words in Spanish:

• porque = because
• por qué = why

In this sentence, the word gives the reason:

• La mecánica abrió el capó porque el coche hacía un ruido raro.
• The mechanic opened the bonnet/hood because the car was making a strange noise.

If you were asking a question, you would use por qué:

• ¿Por qué abrió el capó?
• Why did she open the bonnet/hood?

Spanish uses definite articles very regularly. Here, el coche simply means the car.

The article is needed because we are talking about a specific car in the situation. Omitting it would be incorrect:

• el coche = the car
• not coche by itself in this sentence

Spanish generally requires an article with singular countable nouns in cases like this.

Here, raro means strange, odd, or weird, not rare in the English sense of uncommon.

So:

• un ruido raro = a strange noise

This is a very common false friend for English speakers. Sometimes raro can overlap with uncommon, but in everyday use it very often means odd or weird.

In Spanish, adjectives usually come after the noun, so:

• un ruido raro = a strange noise

That is the normal, neutral order.

If an adjective comes before the noun, it often adds a more literary, emotional, or subjective tone. So un raro ruido is possible in some contexts, but it sounds less neutral and less everyday here.

For learners, the safest default is:

• noun + adjective
• ruido raro

Both can work in English, but was making is usually closer to the Spanish here.

Because hacía is imperfect, it suggests an ongoing background action:

• because the car was making a strange noise

That said, natural English sometimes uses the simple past:

• because the car made a strange noise

But if you want to reflect the Spanish tense contrast more clearly, was making is the better choice.

Yes, that is completely possible.

Both of these are grammatical:

• La mecánica abrió el capó porque el coche hacía un ruido raro.
• Porque el coche hacía un ruido raro, la mecánica abrió el capó.

The meaning stays the same. The difference is mostly one of emphasis and style:

• putting porque... at the end sounds very natural and neutral
• putting the reason first emphasizes the cause a bit more

The written accents show where the stress falls:

• capó → stress on the last syllable: ca-PÓ
• abrió → stress on the last syllable: a-BRIÓ

A rough English-style guide:

• capó ≈ kah-POH
• abrió ≈ ah-BRYOH

Also note:

• rió in abrió is one syllable here: brió
• the accent mark helps show the correct stress pattern

Spanish often leaves out subject pronouns when they are not needed, because the verb ending already gives the person and number.

So instead of saying:

• Ella abrió el capó

Spanish can simply say:

• La mecánica abrió el capó

And even if the subject had already been mentioned, Spanish might still say just:

• Abrió el capó

because abrió already tells you it is he/she/it opened, and context tells you who. This is very normal in Spanish.