C130J bleed down issue/fumes in C-130 Technical Posted June 14, 2022 Hey all, We recently had an issue with a plane C130 J model when it comes to bleed downs as well as fumes and smell of burnt rubber when up speeding 2 of the engines. Crew report smell of burnt rubber when they up speed. We did a bleed down and it's not very close to passing. The bleed down with all 4 engines open is about 15 seconds, all 4 engines closed 14 seconds. If we isolate further and close the L and R Wing iso valves it drops to about 12 seconds. This led me to believe the problem is somewhere between the APU and bleed air ducting in the cargo. I've tried to feel for leaks along all accessible ducting and have yet to find any leaks. Any inputs/suggestions on what could cause such a bad bleed down as well as a smell of burnt rubber when upspeeding the engines? I have hand felt the associated ducting/iso/divider vales, external air connect check valve. Next on the list was the apu bleed air check valve. Any input would be greatly appreciated!