Madem fren balatası eski, değiştirelim.

Madem introduces a reason that is treated as already accepted, something like since, given that, or if that's the case.

So Madem fren balatası eski, değiştirelim is structurally like:

• Since the brake pad is old, let's replace it
• Given that the brake pad is old, let's replace it

Compared with çünkü, the word madem often feels more like well, if that's true / since that's so... It often sets up a conclusion or decision.

In Turkish, present-tense to be is often omitted in the 3rd person.

So:

• fren balatası eski = the brake pad is old

There is no separate word like English is here. This is completely normal Turkish.

You can think of it as:

• X eski = X is old
• hava güzel = the weather is nice
• araba pahalı = the car is expensive

Turkish only shows the copula more clearly in some other persons or tenses.

Fren balatası is a Turkish noun compound, literally something like brake pad.

A very common Turkish pattern is:

• first noun modifies the second noun
• the second noun takes a compound ending

So:

• fren = brake
• balata = pad / lining
• fren balatası = brake pad

This is called an indefinite noun compound. The second noun usually takes -(s)ı / -(s)i / -(s)u / -(s)ü depending on vowel harmony.

Other examples:

• araba kapısı = car door
• ev anahtarı = house key
• çay bardağı = tea glass

So balatası does not mean his/her pad here. In this structure, it is just the normal compound form.

Because eski is a plain adjective here: old.

In Turkish, adjectives do not change for singular/plural or gender, and they usually do not need extra endings when used before or after a noun in this kind of sentence.

So:

• eski araba = old car
• araba eski = the car is old
• fren balatası eski = the brake pad is old

There is no equivalent of English adjective agreement here.

Değiştirelim means let's change it / let's replace it.

It comes from:

• değiştirmek = to change, replace
• -elim / -alım = let's ... form (1st person plural suggestion/command)

So:

• gidelim = let's go
• bakalım = let's see
• değiştirelim = let's replace it

This form is used when the speaker includes themself in the action.

Because değişmek and değiştirmek are different verbs.

• değişmek = to change, become different
• değiştirmek = to change something, replace something

Here, the brake pad is the thing being replaced, so Turkish uses the causative/transitive verb değiştirmek.

Compare:

• Hava değişti. = The weather changed.
• Lastiği değiştirdik. = We changed/replaced the tire.

So değiştirelim is correct because there is an object understood: the brake pad.

It is not stated, but it is understood from context.

Turkish often leaves out objects when they are obvious. Here, everyone knows that the thing to be replaced is the brake pad.

So:

• Madem fren balatası eski, değiştirelim. = Since the brake pad is old, let's replace it.

If you wanted to say the object explicitly, you could say:

• Madem fren balatası eski, onu değiştirelim.
• Madem fren balatası eski, fren balatasını değiştirelim.

Both are possible, but leaving the object out is very natural when it is obvious.

Good question. In Turkish, the accusative is used on a stated definite object, but if the object is simply omitted, there is nothing to mark.

So compare:

• Fren balatasını değiştirelim. = Let’s replace the brake pad.
• Onu değiştirelim. = Let’s replace it.
• Değiştirelim. = Let’s replace it / let’s change it.
  The object is understood, so no accusative appears.

The specificity is still there in meaning, but Turkish does not have to repeat the object.

Turkish often puts the reason first and the main action last.

So the structure is:

• Madem fren balatası eski = since the brake pad is old
• değiştirelim = let’s replace it

Turkish is generally a verb-final language, so the main verb commonly comes at the end.

A very literal structural view would be:

• Since brake pad old, let’s-replace-(it).

That may feel unusual to an English speaker, but it is normal Turkish word order.

Yes. Madem ki is also possible.

• Madem fren balatası eski, değiştirelim.
• Madem ki fren balatası eski, değiştirelim.

Both are natural. The version without ki is very common and concise. Adding ki can sound a little more explicit or emphatic, depending on context.

Not exactly.

• çünkü usually means because
• madem usually means since / given that / if that’s the case

Compare the logic:

• Fren balatasını değiştirelim, çünkü eski.
  Let’s replace the brake pad, because it’s old.

• Madem fren balatası eski, değiştirelim.
  Since the brake pad is old, let’s replace it.

So çünkü introduces the reason after the main statement, while madem often introduces the accepted reason before the conclusion.

Turkish often uses the singular when talking about a part or item in a general or context-specific way.

So fren balatası eski can naturally mean:

• the brake pad is old
• the brake lining/pad in question is old

If you specifically wanted the plural, you could say:

• fren balataları eski = the brake pads are old

But the singular is not strange here, especially if one pad or one set is being discussed as a unit.

It sounds natural and fairly conversational, but not sloppy.

• madem is common in everyday speech
• omitting the object in değiştirelim is also natural
• the whole sentence sounds like something a mechanic, driver, or friend might say

A more explicit version could be:

• Madem fren balatası eski, onu değiştirelim.

A more technical or formal context might use more specific wording, but your original sentence is perfectly normal Turkish.