Intermittently brakes getting hard during stops in traffic

Hi,

First, this vehicle wasn't offered in the US for 2015, so I have very little technical information related to it. However, I will do my best to help.

What you described sounds like there could be an engine vacuum leak. Here is how the power brakes work on a vacuum assist brake booster. Engine vacuum is supplied to the booster from the engine. When it is supplied, the booster actuates and allows the brake pedal to be pushed much easier.

So, the first thing I recommend is to first check to make sure the larger vacuum hose between the engine and the brake booster isn't leaking.

If you look at pic 1 below, I found a picture of the brake booster and brake master cylinder online. The brake fluid reservoir is upside down in the pic. I circled the booster vacuum hose I need you to check.

Start with this. Also, here is a link you may find helpful when testing for vacuum-related issues:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know what you find or if you have other questions.

Take care,

Joe

See pic below. Note: The component will be located under the hood of the vehicle and mounted on the firewall between the engine compartment and passenger compartment. I'm not sure if you have left-hand or right-hand drive vehicles, but it will be on the driver's side of the vehicle.