Spent a whole year torquing injector lines wrong on our Detroit 60s

Always did the final torque on the line nuts with the engine hot, figured it was the right way to account for expansion. Had a weird leak on a Series 60 last week that wouldn't go away. The old head tech from the Freightliner dealer in Boise was in and just asked, 'You doing those cold or hot?' Turns out the manual specifically says final torque at ambient temp. I must have missed that page. How many other little things like that are we all just doing wrong?

4 comments

4 Comments

ward.tara2mo ago

Oh man, that's a classic. The hot torque thing makes so much sense in your head, right? I've seen guys do the same on aftercooler housings, thinking they need to be snugged up hot. The manuals are so picky about ambient spec for a reason, it's all about the clamp load settling right as things cool down.

avery_allen2mo ago

Yeah it's such an easy trap to fall into lol. I watched a guy fight a turbo exhaust flange for an hour because he kept trying to torque it while the engine was hot. The bolts just kept stretching and it never sealed right until he let it cool.

beng5128d ago

What gets me is the guys who double down on it. They'll argue that the hot torque accounts for thermal expansion and creates a perfect seal. But that's exactly backwards. You torque it cold so the joint compresses as it heats up, that's where the seal comes from. Torque it hot and you're already past the material's yield point before it even sees operating temps. It's not just about following the manual, it's about understanding why the manual says what it does.

janag432mo ago

Honestly, feel your pain on that one. Tbh we've all been burned by a tiny detail in the manual.