I own a 2012 Hyundai IX20 blue motion 1.6 diesel. I bought it second hand in 2014 with 16000 miles on the clock and a full service history. Since then it has been serviced on time by the main dealer. It has covered 42000miles.

At the start of this year, a slight vibration/noise started to become evident at about 1600rpm, disappearing at about 1800 rpm. It was slight and I thought it might be a leaking exhaust but I could find nothing. Consequently I decided to wait until it got worse. As a result I mentioned it at the service in the summer. The dealer gave it a test and said it needed a bush which he had to order. In due course this was fitted and the car did seem quieter, though the vibration had not gone away completely. Curiously, when having the bush fitted, the main dealer told me it was to cure the knocking sound that I had reported. I told them I had not reported a knock but a vibration when they quickly agreed it had been a vibration.

The noise slowly got louder again and the car seems to vibrate under the seats, again at this rpm band. It is quiet when on the overun but the noise/vibration is very noticeable when pulling hard, say uphill in 3rd, 4th, 5th or 6th gear. I reported it to the main dealer again this week. A mechanic came out with me on a short run and said he thought it was an induction noise. The car wasn’t driven under stress in 3rd gear or higher because of the route and, when I suggested a longer route, the mechanic said there was no need. He then put the car on the ramps and apparently tested all the turbo joints for a leak but could not find anything. I was given the car back and told not to worry as nothing would go wrong and if the noise became worse to return again before the warranty is up.

I am not mechanically illiterate and cannot see how an induction leak could cause such a noise and vibration and yet remain undetectable. Consequently I am concerned it may be something greater and expensive. I want to ensure that any recourse I may have under the warranty is not jeopardised. Apart from this the car runs well, though the Blue Motion only seems to work on the odd summer day. I have driven many cars, petrol and diesel, over my 48 year driving life and have never experienced anything quite like this before.

Are you able to advise me please?