Mi amiga dijo que el freno no respondía igual cuando íbamos muy rápido.

Because amiga is feminine, meaning female friend. The possessive mi does not change for masculine/feminine in the singular, so:

• mi amigo = my male friend
• mi amiga = my female friend

So mi stays the same, but the noun changes.

Dijo is the preterite form of decir for él/ella/usted: he/she said.

It is used because the sentence refers to a completed act of speaking in the past: your friend said something at a particular moment.

• Mi amiga dijo... = My friend said...

If you used decía, that would sound more like was saying / used to say, which has a different nuance.

Here que means that and introduces the reported statement.

• Mi amiga dijo que... = My friend said that...

In English, that is often optional: My friend said the brake...
In Spanish, que is normally required after verbs like decir when introducing what someone said.

El freno means the brake. It is singular because the speaker is talking about the brake as one system or one specific brake.

In context, Spanish often uses the singular where English might also use singular:

• el freno = the brake / the braking system / the brake pedal, depending on context

The exact interpretation depends on the situation, but grammatically singular is completely normal.

Respondía is the imperfect of responder. It suggests an ongoing, repeated, or background situation in the past.

Here it means something like:

• wasn’t responding the same way
• didn’t respond the same way (in general / under those conditions)

Why imperfect here?

Because the sentence is describing how the brake behaved when they were going very fast. It is not focusing on one single completed response, but on a general pattern or ongoing behavior in that situation.

Compare:

• no respondía igual = it wasn’t responding the same / it didn’t behave the same
• no respondió igual = it didn’t respond the same on one specific occasion

Yes. In Spanish, responder can be used for machines, controls, systems, and body parts to mean respond, react, or work as expected.

So el freno no respondía igual means the brake was not reacting in the same way as before or as expected.

This is a very natural use of responder.

Here igual means the same or in the same way.

So:

• no respondía igual = it wasn’t responding the same / it didn’t behave the same way

It does not mean equal in a mathematical sense here. It is being used adverbially to describe how the brake responded.

Íbamos is the imperfect of ir for nosotros: we were going.

It is used because this part gives the background situation:

• cuando íbamos muy rápido = when we were going very fast

The imperfect fits well because it describes the ongoing circumstances during which the brake was behaving differently.

If you said cuando fuimos muy rápido, that would sound much less natural here, because fuimos is preterite and suggests a completed event rather than the ongoing background speed.

It has an accent because that is the correct spelling of the imperfect form of ir:

• yo iba
• tú ibas
• él/ella iba
• nosotros íbamos
• vosotros ibais
• ellos iban

The accent in íbamos helps preserve the correct stress: EE-ba-mos.

Because rápido is working as an adverb here, modifying íbamos:

• íbamos muy rápido = we were going very fast

When words like rápido, lento, alto, etc. are used adverbially in everyday Spanish, they often stay in the masculine singular form.

So:

• habla rápido = he speaks fast
• conducían lento = they were driving slowly
• íbamos muy rápido = we were going very fast

You could also hear muy deprisa, which is another common way to say very fast.

Because Spanish often omits subject pronouns when the verb ending already makes the subject clear.

• íbamos already tells you it means we were going

So cuando íbamos muy rápido is completely natural.
You could say cuando nosotros íbamos muy rápido, but it would usually only be for emphasis or contrast.

They are similar, but not identical.

• no respondía igual = it wasn’t reacting the same way
• no funcionaba igual = it wasn’t working the same way

Responder focuses more on the brake’s response or reaction, especially when used.
Funcionar focuses more generally on whether it worked.

In this sentence, respondía is a good choice because it suggests the brake felt different when the car was moving very fast.

This is normal Spanish word order:

1. Mi amiga dijo = main clause
2. que = introduces the reported clause
3. el freno no respondía igual = what the friend said
4. cuando íbamos muy rápido = the time/circumstance

Spanish often places the circumstantial part at the end, just like English can:

• My friend said that the brake didn’t respond the same when we were going very fast.

You could move cuando íbamos muy rápido earlier for emphasis, but the given order is very natural.

Yes, but it would change the meaning slightly.

• el freno = the brake / braking system / brake pedal
• los frenos = the brakes

In many contexts, both are possible depending on what the speaker wants to focus on.
The singular in your sentence sounds natural if the speaker is thinking of braking as one control or one system.

It combines a preterite main verb with imperfect verbs in the subordinate clause:

• dijo → preterite
• respondía → imperfect
• íbamos → imperfect

This is very common in Spanish.

Why this combination?

• dijo gives the completed past action of speaking
• respondía and íbamos describe the ongoing situation or background content of what was said

So the sentence structure is very typical for narration in the past.