NHTSA complaint #11452185

Owner complaint summary

Purchase new Tucson from Hyundai of Saint Augustine FL in April 2021, the vehicle worked fine. Then in July 2021 the vacuum assist brakes would not hold a vacuum after the engine was shut down, so when you went to start the vehicle it required excessive pressure on the brake peddle to clear the interlock before the vehicle would start. Took vehicle to dealer and told service writer that I thought it was the Check Valve leaking. After 2 hours service writer told me Tucson was ready and their technician did not find anything wrong and that there is no Check Valve. Drove vehicle home and the vacuum assist brake was still not correct so I filed a case with Hyundai USA (#18769467) about the problem and waited for them to contact me. When they contacted me they told me to take it back to dealer and they would fix the problem. I know enough about vehicles that use engine vacuum for power assist brakes have a check valve, so before I went back to dealer I looked up the part number (59139-2W000) vacuum intensifier, and the Hyundai patent (US7752841B2) which clearly shows a check valve. Went back to dealer in October as instructed by Hyundai and told the service writer the same thing I told him the first time. Waited 2 hours again and was told the technician did not find anything wrong and there is no check valve. I then showed him the part number and said that is the check valve. He said he would check with the service manager to see if Hyundai would cover the cost to replace the part and would call me later. Got the call and was informed that Hyundai would NOT pay to replace the part because the dealership technician did not find any thing wrong. How could the technician find anything wrong with a check valve when he said there is no check valve in the brake system. If the engine quit while I was driving I would not have power assist brakes which could cause an accident. I bought the part from different dealer & installed it, brakes work fine now.