"R39" was again used in 1939 in "Blue Bird K4". In 1947 Campbell unsuccessfully converted "K4" to jet power using a de Havilland Goblin engine. After Campbell's death from natural causes in 1948, Donald Campbell bought "K4" for a nominal sum as well as the 1935 record car when his father's effects were auctioned. He also purchased "R37" back from a car dealer and reinstalled it in "K4". Attempts on the record were made in 1949, and again in 1951 when "R37" was "damaged beyond any immediate repair" by overheating. Another attempt was made later in the year using "R39", but "K4" suffered a structural failure and sank in Coniston Water. It was recovered and broken up on the shore.