1960 Kelleners began his motorsport career in rallying and moved to four years in touring car racing. His first touring car races he contested in 1964 with a glass of TS 1304 in Zandvoort, which he won.
Kelleners launched from 1964 to 1984 in many racing series, which achieved many victories and top placings in championships. His first major racing success was the second place in the third division of the European Touring Car Championship in 1968, when he took up with a Porsche 911.
In addition, he also drove from 1967 to 1982 single race - especially in the 1000 km race at the Nurburgring and in the years 1968, 1969, 1970 and 1975, all racing series in the World Sportscar Championship. He started three times in the 24- hour race at Le Mans. 1969 reached Kelleners together with Reinhold Joest in the Ford GT 40 in the 24- hour race at Le Mans 6th place overall and 3rd place in the S5.0 class. This result was also his best finish, which he achieved in his start at Le Mans.
Another 24 -hour race victories he experienced in 1968 and 1970 in the 24 -hour race in Spa- Francorchamps with Porsche 911 and later BMW 2800 CS and 1972 in the 24 -hour race at the Nürburgring, also with a BMW 2800 CS.
In 1970, he rose with a March 707 Chevrolet into the newly founded Inter series, where it was on the 3rd place in the overall standings. In subsequent years, he moved to McLaren and McLaren M20 Chevrolet Chevrolet M8F and even drove to 1975 race in the Inter series.
1972 to 1976 and after a break from 1979 to 1981 drove Kelleners BMW and Porsche racing cars in the German Racing Championship. At his best result of the season in 1975, he drove a Porsche 911 Carrera RSR Jagermeister Kremer team to 5th place in the overall standings.
In the European Championship for GT cars it was established in 1976 with a Porsche Turbo RSR behind Toine Hezemans vice-champion. His biggest success in motorsport celebrated Kelleners with piloted BMW race car in the European Touring Car Championship in 1980 and 1982 in which to have won three times in a row the championship. A year later, he again reached a third place with a BMW 635 CSi in the overall standings.
1984 ended Kelleners his successful racing career. His son Ralf Kelleners is also a racing driver since 1987.