the_logan•1mo agoProlific Poster

Question about a weird vibration fix on a 6.7 Powerstroke

I was under a customer's truck in my shop in Boise and the whole thing was shaking like crazy at idle. I checked the usual stuff, mounts, injectors, you name it. Then my buddy who runs a sawmill said to check the fan clutch, and sure enough, it was locked up solid. Has anyone else had a bad fan clutch cause a shake that bad on a newer diesel?

3 comments

3 Comments

mila_perry131mo ago

Oh man, that's wild... my buddy had the exact same thing happen on his F-250 last winter. He was convinced it was a bent rim or something with the tires because the shake was so bad at stoplights. Spent a bunch of money chasing that before another mechanic just reached in and stopped the fan by hand with the engine off. It was completely seized, and the new one fixed it right up. It's crazy how something that simple can shake the whole truck like that.

hill.andrew1mo ago

Yeah when you said "shake the whole truck" that really clicked. I read a whole forum thread once where a guy with a diesel was ready to sell his truck over a shake at idle, and it was just the fan clutch locked up solid. @mila_perry13, your buddy's story is so common it's painful. The weight of that fan spinning off balance makes the engine rock like crazy, and it feels exactly like a wheel problem. It's one of those cheap fixes that gets missed because the vibration feels way too big for a little part.

rowanellis17d ago

Hang on though, you can't stop the fan by hand with the engine off, that's just because the engine isn't spinning it. You gotta check it when the engine is hot and running, or at least try to spin it when the engine is off and cold to feel if it has resistance. If it's really locked up solid, it won't spin freely even when cold. The real test is if it keeps roaring on a cold start and never slows down, then you know it's stuck. Just want to make sure people don't go swapping parts off a cold engine and think they've got it fixed.