Diesel runaway! expected damage?

eric28miller

eric28miller

HP lover
Hey guys, had terrible day.. I bought a rolled lbz duramax, was working on getting it running so I could pull it into the shop to start body work. Was running perfect, letting it warm up, been sitting a long time so I was easing into the throttle to clean things out when all of a sudden the rpm's sky rocketted to what sounded like 10k rpms. I quickly tried to shut it off which obviously did nothing. By the time I ran around and pulled the intake off to shove in my shirt it died on it's own so it only over revved for 12-15 seconds, although it felt like minutes. I right away knew oil must have ran into the intercooler while it sat upside down. I've had this happen with turbos going on on equipment once the oil got hot enough but I never would have guessed it would do it on cold oil, I was very wrong. :bang I let it cool down and bumped the starter a few times to access the damage, I figured the bottom end is fine because it never lost any oil and I didn't hear any rod knock but as it cranked it made a blop noise from the intake sounding like some valves not opening. I believe the valves floated and either bent some pushrods or could they have just fallen off the rockers? I've never been in a duramax engine and was hoping you guys could shed some light on this. It's got 170k miles so i'm going to go ahead and pull the heads off and do a head gasket job with some arp studs. I'm worried the valves kissed the pistons, what are your thoughts? Thanks
 
pardon my poor spelling *assess*the damage [ame="http://s1030.photobucket.com/user/eric28miller/media/Mobile%20Uploads/E57ED7C0-E705-42EC-B485-D771E6EA20CA.jpg.html"]E57ED7C0-E705-42EC-B485-D771E6EA20CA.jpg Photo by eric28miller | Photobucket[/ame]
 
E57ED7C0-E705-42EC-B485-D771E6EA20CA.jpg
 
Probly just bent pushrods. Id replace em and do a compression test before pulling the heads.

Sent from my SM-G930P using Tapatalk
 
ok i'll see how bad they look, Hey Mark how'd you get that pic to post? I couldn't get it to work? It because i'm a newbie
 
I tried every way but that lol Thanks Mark!
So pulled out the passenger side injectors and valve cover last night and this is what I found...
[ame]http://i1030.photobucket.com/albums/y366/eric28miller/Mobile%20Uploads/09A67240-831C-4484-BAAE-DABAEF822E24.jpg[/ame]
[ame="http://s1030.photobucket.com/user/eric28miller/media/Mobile%20Uploads/09A67240-831C-4484-BAAE-DABAEF822E24.jpg.html"]09A67240-831C-4484-BAAE-DABAEF822E24.jpg Photo by eric28miller | Photobucket[/ame]
[ame]http://i1030.photobucket.com/albums/y366/eric28miller/Mobile%20Uploads/8864274B-A670-4E98-A718-FADD890925C6.jpg[/ame]
[ame="http://s1030.photobucket.com/user/eric28miller/media/Mobile%20Uploads/8864274B-A670-4E98-A718-FADD890925C6.jpg.html"]8864274B-A670-4E98-A718-FADD890925C6.jpg Photo by eric28miller | Photobucket[/ame]
Idk what's going on with my pics, I used direct and IMG.. You'll have to click on the links to see the carnage.
Definitely bent push rods but I was more shocked by the injectors! Now i'm really scared of what the pistons look like.. My buddy is bringing over his borescope sometime this weekend to take a peek inside. I hope to god there's not any more damage!.. What do ya'll think?
 
Last edited:
I just got done peeking inside with the borescope. It was hard to see much but I could definitely tell the valves kissed the pistons. Though I didn't see any signs of melting on the pistons so hopefully the cylinders are ok. Now i'm very worried about the heads being ok.. Think the valves could have bent or do the pushrods have enough give to bend before damaging a valve?..
 
Valves are probably bent but its easy to check. Pull all the rockers and do a leakdown test.

Sent from my SM-G930P using Tapatalk
 
I have had a couple of engines run away on me over the years, it is not a sensation that you ever get used to. I had one engine a few weeks ago, little Kubota dpf engine in a cat skid steer decided to kick back when I tried to start it and it took off, RUNNING BACKWARDS, at 4600 rpm according to the engine ecm.

The majority of the damage should be concentrated to the valve train as Busted said, the rotating assembly is most likely fine. Even if the heads are damaged, they aren't exactly unobtainable these days.
 
If an engine runs backwards, doesn't that usually mean that the oil pump does, as well?
Which means 4600 RPM, for however long, with NO lubrication.

I imagine an engine doing that would have at least a few chewed up bearings.

Mark.
 
The engine I had run backwards was completely trashed. It ran until death by friction. I was referring to his dmax that ran away, most of the damage on his engine should be isolated to the valvetrain.
 
You don't appreciate an air shutoff till you go through a runaway. I had one in my old drag truck, was taking a quick checkout ride on a back road before going to test and tune, ran to top of third and lifted and kept on going. I shut off the electric fuel pump and it didn't phase it, power braked it down and was on the side of the road doing a burnout, trying to save it and didn't want to just put it in nuetral. This went on for a couple of minutes my buddy with me thrue his shirt in the turbo and it slowed down to about 3000rpm. Drove it back to my driveway with the hood up smoking like hell, pulled it in a ditch and got it stuck on purpose and finally found a razer blade to cut the fuel line. When said and done I should of just put in nuetral and let it go, trying to save it I fried the trans, destroyed the turbo, and from getting so hot cracked the block. Stuck rack in p-pump.
 
You must log in or register to reply here.
Back
Top