Navistar is recalling certain model year 2006 through 2011 IC school buses, models CESB, RESB, and FESB, manufactured from June 17, 2004, through October 15, 2009, equipped with I-6 engines within feature codes 12N (PL, PM, PN, PR, PS, PT, PU, PV, SA, SG, SK, SL, SM, SV, SZ, TB, UA, UB, UC, and UD). The high pressure engine oil line may develop a leak or possibly rupture.