Just found out injector cups on a 5.9L 12 valve can fail without any smoke or miss

I was reading a thread on the Cummins forum and a guy said his truck lost power climbing a grade in Colorado last summer, turned out the cups were cracked but it never blew white smoke or sounded rough, has anyone else run into a silent injector cup failure like that?

4 comments

4 Comments

alicecraig4d agoRising Star

Yeah @sethfoster is right, it's like how bad tires can suddenly blow with no warning at all.

ray_williams3d ago

Whoa, I used to be one of those guys who thought a 12 valve was basically bulletproof no matter what. But reading about the coolant in the oil issue and that Colorado story really changed my mind, it makes you realize even the tough ones can have silent problems. I'm definitely going to start checking my coolant level and oil way more often now just to be safe.

sethfoster4d ago

Did you happen to catch that thread on the old Cummins forum where a guy said his injector cups leaked coolant into the oil and wrecked his bearings before any smoke showed up? I remember reading about that Colorado story too, seems like the cups can crack in a way that doesn't cause the usual symptoms. Might be worth checking the coolant level and oil condition more often on those 12 valves.

logan_mitchell4d ago

I mean, idk, that sounds like a pretty rare freak thing more than something to lose sleep over. Maybe it's just me but I've heard way more stories about those 12 valves just running forever with basic maintenance than horror stories like that.