Fren testi geçti; hâlbuki fren tertibatında ağır kusur bulundu.

Turkish often leaves the subject unstated when it is clear from context. Here, the implied subject is something like the vehicle, the car, or simply it.

So geçti means passed, and the full idea is something like It passed the brake test.

This is much more natural in Turkish than in English, where you usually need to say the subject explicitly.

Fren testi is a noun compound meaning brake test:

• fren = brake
• testi = test, with the compound ending -i

That -i is part of the compound structure, not automatically the accusative case.

In very careful standard Turkish, if this whole phrase is the definite object of geçmek, many speakers would prefer fren testini geçti.

So why does your sentence have fren testi geçti? It is a compact, report-like style. You may encounter this kind of shortening in official or condensed language. As a learner, though, fren testini geçti is the safer form to produce yourself.

It is the past tense of geçmek.

Geçmek has several meanings, such as:

• to pass
• to go past
• to cross
• to elapse

Here it means to pass, as in passing a test or inspection.

So geçti = passed.

Hâlbuki introduces a contrast, often one that feels surprising or contradictory. In English it can correspond to:

• however
• whereas
• and yet
• even though that was the case

Compared with ama, it is usually more formal and more written in tone.

So the sentence is not just adding another fact. It is saying: this happened, and yet the opposite kind of fact was also true.

You will also often see this word written as halbuki in modern texts.

It breaks down like this:

• fren = brake
• tertibat = apparatus, mechanism, setup
• fren tertibatı = brake mechanism / brake equipment / braking system
• fren tertibatında = in the brake mechanism / in the braking system

The ending -da is the locative, meaning in, on, or at.

So this part tells you where the defect was found.

This is because tertibatı already contains the 3rd-person possessive-type ending used in noun compounds.

The structure is:

• tertibat-ı = its apparatus / apparatus of something, here part of the compound fren tertibatı
• then locative -da

When Turkish adds a case ending after this kind of -ı / -i / -u / -ü, it usually inserts a buffer n:

• tertibatı + da → tertibatında

So -nda is exactly what you expect after this kind of noun form.

Literally, ağır often means heavy, but in many contexts it means serious, grave, or major.

So ağır kusur is a set phrase meaning something like:

• serious defect
• major fault
• grave deficiency

This is especially common in technical, legal, and inspection language.

Bulunmak is very common in formal and official Turkish. In this kind of sentence, it can mean:

• to be found
• to be present
• to exist

So ağır kusur bulundu has an official-report tone, something like:

• a serious defect was found
• a serious defect was present

If you said ağır kusur vardı, that would be simpler and more everyday: there was a serious defect.

So the difference is mostly one of style and tone.

Historically, it is related to the verb bulmak = to find, but in modern Turkish, bulunmak is best learned as its own verb.

In real usage, bulundu often behaves like a fixed formal verb meaning:

• was found
• was present
• existed

So yes, its English translation may look passive, but for learning purposes it is more useful to recognize bulunmak as a normal Turkish verb you will often see in formal writing.

The semicolon links two closely related clauses while marking a clear contrast between them.

The effect is formal and written:

• first clause: one result or appearance
• second clause: a conflicting fact

A comma might also be possible in less formal writing, but the semicolon makes the contrast sharper and cleaner.

So the punctuation helps underline the contradiction: it passed the brake test; however, a serious defect was found in the braking system.

In ağır, the ğ is usually not pronounced like an English g. It usually lengthens or smooths the vowel before it. So ağır sounds roughly like aa-ır.

In hâlbuki, the â traditionally suggests a somewhat longer a, but in everyday speech many speakers do not make a very strong distinction. Also, many people simply write halbuki.

So for practical purposes:

• do not pronounce ğ as a hard g
• do not worry too much about making the â very dramatic

Understanding the word is much more important than producing a perfect length contrast here.