Facing braking issues on my 8-year-old Renault Duster

The brake pedal becomes rock-hard during cold starts. Guys at the Renault service centre said that it could be due to the car's age and mileage.

BHPian xjosephjacob recently shared this with other enthusiasts.

My 8-year-old Duster 85PS has a problem related to braking (before cold start) which cropped up recently. The car has run 1.2 lac km so far.

Say, for example, I completed a trip and have parked the car in the garage overnight (in the 1st gear). The next day, before starting the car my natural tendency is to: press the brake pedal > press the clutch > shift the gear to neutral > turn on the key. Normally, the braking system would have just enough vacuum (or lack of it) to allow me to apply brakes once before cold starts. Only if I pump 2 or more times, the pedal becomes hard.

However, recently, before I perform the cold starts my brake pedal stays rock hard. Or in other words, the braking system is unable to engage the brakes. This is a safety hazard because if the car is parked on an incline, it would simply roll-off (unless I apply the handbrakes). Once the car is turned on, the brakes work just normally. There are no other easily recognizable symptoms in the braking system as I understand. No hissing sound, nothing.

Gave the car to the Renault service center, and as expected they said these are due to the car's age and mileage without pinpointing which exact part in the braking system is failing. They said let's get a new brake booster first (which I should pay from my pocket), and see how things are - in case the problem persists, let's get to the child parts.

With this kind of response, I think the folks at this service center are rather incompetent, which is why I'm reaching out to the TBHP community.

What do you think could be the root cause?

Here's what BHPian vigsom had to say about the matter:

Brake pedal working fine after engine turning on = booster is normal.

You could just inspect the vacuum hose from the brake booster to its end connection on the engine side and also check the hose end connections too for wear/leaks. Also please check for a minor pinhole or so on the brake booster body around the seam (unlikely you'll see this but just a possibility). I didn't expect the service center to give you a proper solution.

Here's what BHPian Kosfactor had to say about the matter:

Vacuum pump, reservoir, brake booster and vacuum hoses. All these things need to be checked by a competent mechanic.

Here's what BHPian gkveda had to say about the matter:

If you park the vehicle in an uphill (upward slant) position, brakes becoming hard during cold start is normal. You need to worry only if the car is parked in a flat position and still brakes becoming hard during cold start.

As kosfactor suggested, the vacuum pump, reservoir, brake booster and vacuum hoses, all need to be checked, if your case belongs to the second scenario above.

Here's what BHPian Indian2003 had to say about the matter:

You don't say if this is a petrol or diesel car. If petrol it is very easy to check for leaking vacuum lines.

Let the car run on idle and spray start gas at the hose joints or where you suspect a leak. If leaking, the idle speed will go up. You need to spray on all the hoses and not only those going to the booster.

Your problem seems to be a leaking booster or hoses but I place my bet on the hose. Always check the cheapest solution when looking for faults. Don't believe what your workshop said about a faulty booster.

These are very reliable units and seldom needs replacing. The booster in my car has done 300,000 km more than yours.

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