When a diesel decides it’s time for self-destruction... 🚨

Runaway diesel engines are a mechanic’s nightmare and a trucker’s worst-case scenario. It happens when leaking motor oil from the turbocharger makes its way into the engine, turning motor oil into uncontrollable fuel. The result? A screaming engine revving to self-destruction. Shutting off the ignition? Useless. Your only hope: cutting off the air supply or stalling the engine in the highest gear.

It’s a rare but catastrophic event that leaves no survivors—not the engine, not the turbo, and certainly not your wallet. Got a runaway engine story? Let’s hear it in the comments.

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[jackwalling]

thanks for reminding me I might need to address that oil leak on my turbo

[benruether]

"The engine has its own agenda now. Fueled by oil and chaos" How poetic and goes hard at the same time

[AndyEightSevenFive]

This isn't as common these days as it was on older mechanical engines. But a simple positive air shutoff valve is a cheap and effective insurance to have installed. Great for theft prevention as well if you use it after you shut down normally and its not a obvious switch in plain sight.

[lakesnake]

Block the air intakes. Maintain your vehicle and this will not happen.

[jefffrearson]

This happened to me once, the scary part was that I was hauling diesel fuel. Thank God the engine blew up before a fire started. I think that was one of the scariest days of my life.

[chrisbetter]

I know a guy who changed his turbo and didn't make sure the charge cooler didn't have oil in it from the bad turbo, guess what. It

[coltonkruse]

Had a turbo fail once. Lucky for me it was blowing all the parts and oil out the exhaust and not through the intercooler. Sometimes you get lucky. Even on a bad day.

[jmowreader]

"Killing the ignition? Useless!" That's because diesel engines are their own ignition system. They don't have spark plugs...and if your engine is burning motor oil as fuel, the only way you're stopping it is to block the air intake and hope like hell it's not pulling in air from somewhere between the intake and the head.

[franksprecisionguesswork]

Some 50 years ago I repaired a big compressor that had a big Cat engine. The governor broke in the injector pump so it wound up wide open. The engine had a compression release so the operator yanks on it and broke the handle off. While the guys were pulling the air filter off, a piston shattered and exited the block. Finally they plugged off the intake and starved it of air. Amazingly only the wet sleeve was shattered along with a softball sized hole in the block. The rod was wrapped around the journal like it has made out of lead. And didn’t even damage the crank.

Installed a new sleeve and piston, welded up the hole in the block, and had ready to run by the time the injector pump came back from repair.

[j.]

I had this happen 20 years ago on a 1 year old combine with 500 hp Iveco diesel engine. Longest 30 seconds i have ever experienced. $45k repair, manufacturer tried to pin it on me.

[duanepierson]

A buddy of mine lost his Jetta TDI to a Turbo induced runaway. I first heard one as a wee lad. Was at the dump w/ Dad & we heard a fierce roar, it was a garage truck, maybe a Mack, turning itself in to junk.

[jeffstratton]

Dude at the end trying to stall it by popping clutch, good idea

[-eb]

Oil seeps into the cylinder and it gets compressed causing ignition and it can be stopped by suffocating the air intake diesel engines require air to compress and ignite.

[Marcoo]

I never knew what this was until it happened to me on my boat 200 nm offshore in the Ocean. Tearing apart cabinets to get at engine, old 80 hp Perkins. Oil was being pushed out of valve covers and coolant spraying at me while I'm right on top of it trying to shut her down.
Finally she slowed down to a peaceful stop.
Will never forget that experience.

[Mathew-xrkt]

Positive air shutoff. Simple solution. Where I work, it’s mandatory all trucks have one. The second it over revs it blocks all air going into the engine. Problem solved

[mikmik]

Diesels were designed originally to run on vegetable oils. They will burn any combustible fluid. They work on high compression not electrics. They stop running when the fuel is stopped from flowing into them.

[HLS]

Had this happen to me a long time ago with a 318 Detroit Diesel in a cab over. I was able to starve its air supply but it ran fast for minutes and scared the crap out of me!

[Mr.PudgeMuffin]

The truck/trailer shop I work at hauls LPG and all the trucks have intake shutoffs for safety reasons but honestly I dont understand why all diesels dont have them. And doesnt even have to be fancy, just a big butterfly valve (which would be the only expence) and grab an E-brake cable from the junkyard or something

[Pete]

My eyes just tear up when I see this nightmare unfolding. I love the sound of diesel idling and working. But this make me mournful.

[hayzeproductions]

Wonder why the fire extinguisher is under the driver seat? You pop the hood and flud the air filter with it to choke the engine out. Never put a truck in high gear, then dump the clutch, the flywheel will rip a hole through the floor board and cut up your legs and feet. Transmission on the ground after that, expensive wrecker service instead of a tow. Not to mention allison and Eaton automatics won't release the clutch if rpms are above the idle limit.