TIL I was torquing injector hold-downs all wrong for like 5 years

Last month I pulled a set of injectors on a 6.7 Cummins and found three of them loose just by hand. Turns out I'd been using a dry torque value the whole time instead of accounting for oil on the threads, and a guy at the Cummins shop in Phoenix set me straight. Anyone else figure out a simple mistake way later than they should have?

2 comments

2 Comments

tyler4928d ago

Dude, that exact thing bit me on a set of 6.7s back in 2019. I was working on a fleet truck in El Paso and the number 5 injector hold-down snapped clean off at 89 lb-ft. The Cummins shop foreman there told me the same thing, you gotta subtract 10% for lubricated threads. I had been torquing them all to the dry spec for probably four years before that. Now I always use a drop of oil on the threads and it feels way more consistent when they seat.

sean_walker457d ago

Read something similar from a Cummins master tech on a forum years ago. He said 90% of injector problems he saw were from either overtorquing or undertorquing the hold-downs because of thread lubrication. Always figured it was just old war stories until I had to helicoil a hole in a head.