The oil seals in your turbo failed.

This allowed oil from your engine to be fed directly into the intake, this burning oil caused the smell/smoke.

When you took your foot off the accelerator, the diesel fuelling stopped but the oil fuelling continued.

With a turbo aspirated car, the exhaust gas spins the turbo which forces air into the engine. The more fuel that goes in, the more exhaust comes out, which blows in more air, etc.

When you stopped the car and turned off the ignition, the engine was still hot and spinning - this meant that the oil kept flowing into the intake where it carried on burning and driving the engine.

Diesel engines do not rely on electrical spark ignition to cause the combustion, they rely on the compression in the cylinder to supply the heat. They will run and run and run so long as they're getting fuel and air.

Your car stopped when either it ran out of fuel (oil), or something melted/seized.

So, the damage....

The turbo is wrecked, the engine is most likely wrecked (redlined with no oil until it died, this kills the camshafts..), the exhaust might be wrecked, and some of the auxiliary/accessories under the bonnet might be wrecked...

If you wanna try and save it, it'll be a good few thousand at an Independent Alfa specialist...

 

What Editor said, sounds like will be a lot of damage, had the same thing happen to me in a Renault Scenic(not mine), luckily I managed to get into gear and stall it before it burnt all the oil off, but still caused a lot of damage.

Good luck.

 

Yep, it will be messy.
Only way of stopping a running-on Diesel is to block the air supply. i.e. by directing a CO2 extinguisher into the intake.
But by that point you really want to be as far away from the engine bay as possible!!!

Getting into gear and stalling it may not be as simple as it sounds.

 

Getting into gear and stalling it may not be as simple as it sounds.

Really? I can't say I've ever experienced the above but this would be the 1st thing I'd try... I certainly wouldn't get out out of the car and look at the smoke blowing out of the exhaust till the engine ate itself...

 

Shame that had to be your first post Stan.

I have a few questions:
How many other people have experienced this?
What can be done to prevent it?

Stan; In hindsight, was there enough time to stall it, get the bonnet open etc. it sounds like this was pretty instant?

 

Getting the bonnet open wont really help, nothing you can do to stop it, stalling it by putting into a high gear and keeping the brakes on can stall it if your quick but it doesn't take long to burn through the sump oil so you have to get it pretty quick.

 

I was wondering if there was time to pull the top turbo hose off or use a fire extinguisher like David suggested. I agree stalling sounds like the easiest option but once it's redlining I don't know how easy that would be.

 

I know on a lot of diesels these days they have a throttle body which when certain conditions are met closes off the air supply to the engine to stop further damage. I know my 1.9 jtdm (2008) has one but I guess it could be used for other purposes. Don't know why yours did not do this or maybe earlier ones did not have this feature.

 

Personally, I wouldn't want to be anywhere near a running on diesel. I've seen it once and its truly scary. There is a risk of injury if the engine blew big time while you were trying to remove a turbo hose or block the intake. Thus, if I couldn't stall the engine then I would get out and watch it go bang from a safe distance

Keith

 

Thanks for the replies guys. Not really what I wanted to hear but It is what it is!

In hindsight, I should have stuck around and tried to stall the car, to be honest it all happened so quick that I wasn't really sure what was going on to start with. By the time I was out the car, the amount of smoke coming out the back was insane, I was certain it was going to blow and at that point there was no way I was going to get back into it.

What I will say, is when I did finally pop the bonnet, it sounded like there was a beeping coming from somewhere. Not sure whether this means the engine cut out before something bad happened (wishful thinking)

I'll be taking the car into a garage today so i'll keep you posted on what the damage is!

 

You did the right thing by getting well away from it... There are ways to try and save a runaway diesel (e.g. stalling or choking the engine), but tbh by the time you realize what's going on there's probably a tonne of damage done... Once it's smoking and redlining you absolutely don't wanna be lifting up the bonnet!!!

 

I'm with Keith most people won't know what is going on other than the car is revving out and it won't stop.

A few people will know how to stall. But the person in question did the safest thing. Pull over. Get out of the car. Stand well back.

The Engine / Car is already toast. So might as well make sure you are safe.
It's only a car after all.
There are many other's in the world. But you'd be far more difficult to find replacement parts for.

 

So how common is this? Can the turbo seals be checked easily? What symptons might be present before catastrophic fail? My lower turbo hose is really oily but I've always assumed this is from the crank case breather not the turbo. Presumably this is a big oil leak that happens quickly.

 

It's called diesel runaway.
Google it and look it up on you tube. Quite scary some of the engine explosions.

 

Can any maintainance help prevent it from happening? (Apart from a new turbo of course!)

 

Fresh oil nice and often never hurts

 

Best way to prevent it is to buy a petrol car

 

...a little unkind! :lol:

Sorry about your predicament Stan :depressed:.

 

I wouldn't even bother taking it to a garage until you have your replacement engine/turbo sorted. No point paying labour to start stripping down whats left of your old one - it will be FUBAR, guaranteed. What you want is a complete good running engine out of a scrapped car, complete with the turbo, injectors etc.

I've always wondered if you can stall one of these by pushing down on the plunger that operates the shutdown flap.

 

I'm not sure I'd want to get under the bonnet if the engine is revving its nuts off.

 

Sorry to hear this, can you claim on insurance?

 

The shut down flap will stall it at idle, can't see why it wouldn't when it's revving up but as said, I wouldn't stick my head anywhere near the engine!

 

runaway diesel.....nightmare ,and nothing you can do unless high gear stall is done sharpish, otherwise its just a case off sitting back and watching the engine banjax itself.

best course of action now is to spring for a new engine if its economical to do so, and the rest of the car is in good condition, if the wishbones are due and a few other bits it will mount up and you will end up spending a fortune on it.

personally I would approach a good alfa specialist and see what A)they will give you as salvage and B)what it will cost to put a new engine in, weigh up the options and go from there.

rotten luck mate and I hope you get it sorted it with the least amount of faff and inconvenience.

 

I used to work in the oil industry on diesel driven fire pumps and they had air flaps fitted for exactly this problem. You would not believe the vacuums that can be generated before the engine stopped and sometimes the air filters would need replacement after a witness test! The big problem in those days was extra fuels in the air, like propane or solvents, not diesel or oil entering the combustion chamber resulting in overruns. Then I changed jobs to diesel driven agricultural equipment, when they fell over, literally down a hill, they would run to destruction on the engine oil. Shame to hear this is still possible in the modern age, turbo oil pressure sensor seems to be the next thing needed on a road car if they don't already have them?

 

I just remembered how we used to detect this and it was done by detecting an overspeed condition of the engine. So my pressure sensor suggestion is probably not required, ECU mod and intake flap is all that is needed.

 

This reminds me I should regularly take a hose off and check for oiling in the hose, there was nothing there 40K ago but who knows now?
This is a scary thought I think I may consider getting rid of the breather being connected to the inlet too.

 

The problem ia not the oil in the turbo inlet hoses but the seals in the high preassure oil feed to the turbo bearings and those are impossible to check without stripping it.

Ric

 

Using the website, How many left? I've estimated 6400 diesel 156s made it to the uk. If you search this forum with the term "diesel runaway" you find 21 threads.

Therefore:
Probability of diesel runaway in the life time of your car = 21/6400 = 0.3%

Thank God! Now I can stop worrying about this.

However:
If you search the term "wishbones" you get 250 threads.

Therefore:
Probability of wishbone failure in the life time of the car = 250/6400 = 4%

Either I've been unlucky with my wishbones or my maths is bad!

 

Either I've been unlucky with my wishbones or my maths is bad!

A lot of people using cheap poor quality wishbones.
My old 156 at over 130000miles has only had one pair of front upper wishbones.
Lower are still original, as are all the rear links.
So not all made of chocolate !!

However, now well off topic.

So no, not every Diesel owner will have the engine run away, but.... some have been removing the shut-off flap... thinking that they will get more power... they may regret that move later!!

 

Yeah but that would assume that all owners would come online and as a question.
Which many wouldn't. Many might not use the internet and others that have the internet would use a search function.

It doesn't happen a lot no. But its a possibility with diesel as they ignite under compression.

 

I can remember quite vividly seeing an 18cyl, 45ltr Cummins engine run-away while in one of their test bays in Daventry. It was absolute carnage and the test bay was also badly damaged by flying chunks of metal. Funny this was - no one panic'd, instead they all stood and watched it (me included)...

 

an episode of scrapheap challenge - scrappy races 2, one entry was a diseasel truck with a big RR engine and that went runaway too (around 20 mins in) when they tried to tweak more power out of it

 

I saw that but it wasn't strictly a runaway, they had been fiddling with the governor and I think it stuck at the end of the pump rack.

If you have a turbo diesel its worth having a mental note of which pipe to pull off and stick something down, t shirt etc if it does run away. I know on mine it is the pipe from the maf at the o/s/f but you would have to be quick.

 

Big fat one at the top and right of the engine.. hoik that off and the runaway will stop quick enough!

Not sure how easy that'll be with the Autolusso silicone hoses and high-grip hose clamps though...