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Am I the only one who sees guys cranking torque specs way too high on injectors? | Diesel Mechanics - Hub Chatter

Am I the only one who sees guys cranking torque specs way too high on injectors?

I was helping a buddy swap injectors on a 6.0 Powerstroke last weekend and he just grabbed his torque wrench and went straight to 30 ft-lbs without even checking the manual. I told him to stop because those hold-down bolts are only supposed to be like 18-20 ft-lbs on most of these big diesels. He argued with me saying "it needs to be tight to seal" but that's exactly how you crack the bore or strip the threads in the head. I've seen it happen twice now at a shop I used to work at in Denver where guys cranked them way over spec and ended up pulling the head off to fix a leak that wasn't even the injector's fault. The real trick is to clean the bore super good with a wire brush and some brake clean, then torque to the exact spec for that engine family. Has anyone else run into this where guys just go by feel instead of looking it up?

2 comments

2 Comments

the_richard2mo ago

Man that's frustrating to watch happen. You were dead right to stop him. I've seen the aftermath of overtightened injector hold-downs on a 7.3 and it's not pretty, usually a cracked bore or a stripped thread that turns a simple job into a weekend nightmare. The worst part is guys think "tight is tight" but on aluminum heads especially, that extra force just distorts the bore and causes a leak that shows up three weeks later. Cleaning the bore like you said is half the battle, a little brake clean and a brush makes all the difference. Did he end up backing off and doing it right after you showed him the manual?

terryr462mo ago

Tight is tight" is exactly the kind of thinking that cracks bores. I read a tech article a while back that said a lot of these hold down bolts are designed to stretch a certain amount and going over spec just ruins that. @the_richard, you're spot on about aluminum heads too. I saw a guy on a Ford forum say he torqued his injectors to 35 on a 6.4 and ended up with a hairline crack that leaked fuel into the oil. Took him a whole weekend to helicoil the head.