I’ve removed the keys but something in the engine is still going!!

[HeidiF]

Apologies if this is a really daft question. We’ve just driven our new (to us) motorhome for about half an hour and stopped to make a coffee and there’s a roaring noise under the bonnet. I’m not very technical (clearly) but I’ve taken the keys out so I can’t think what/how this could be. Help!

 

[MarionK]

When the engine gets too hot particles in the cylinder glow red hot and even with the ignition off fuel will be ignited and detonate! This is not good as the shock waves can damage mechanical parts!

I was more worried about the danger from the shockwave of the engine exploding
The engine already had a bent cylinder head, and after the trip when we kept overheating, we had some major work done, including a beefier radiator.

 

[Oldrat]

It’s called “Pre ignition”

LInk

 

[Andycap]

Talking about air con I have a 2007 fiat Ducato and was wondering if it is possible to fit air con in the cab

 

[HeidiF]

Apologies to you as this may seem like a really daft question too... Did you go for the 5 year old Hymer, or another vehicle. ???

Happy New Van

Cheers
Red.

Impressive memory skills!! Yes we did buy it, new cambelt Tuesday and then we’re ready to go. A steep learning curve ahead of us I think

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[pappajohn]

I find it very hard to believe the engine will continue to run with the key removed no matter what the reason.
Regen happens at higher revs than a fast idle.
It's the cooling fan.

 

[dunnah01]

It’s called “Pre ignition”

LInk

I wouldn't have thought it a common problem on a diesel engine

 

[pappajohn]

I wouldn't have thought it a common problem on a diesel engine

Usually when that happens on a diesel it's a run away .....
It will rev higher and higher until it destroys itself but that only happens if the engine is so worn it can draw oil from the sump via worn bores, worn valve stem oil seals or more likely badly worn turbo oil seals.

Watch to the end

 

[dunnah01]

I love descriptive words like 'ensconced' and often use it.
Its a word that conveys something or someone that is snuggled down somewhere and not just there.

Ensconced - the state of a person whilst eating a scone

 

[dunnah01]

Usually when that happens on a diesel it's a run away .....
It will rev higher and higher until it destroys itself but that only happens if the engine is so worn it can draw oil from the sump via worn bores or worn valve stem oil seals.

I've only ever seen victims when the turbo seals are leaking on the inlet side but I suppose oil from anywhere would be a good fuel in the diesel engine

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[jockaneezer]

You knew when my FS1E needed a decoke, you could take the keys out and it would still run with all the red hot carbon on the piston top. I had to stall it to stop it, but if you switched the petrol tap off, it used to start backfiring and bouncing around on it's stand !

 

[MarionK]

I find it very hard to believe the engine will continue to run with the key removed no matter what the reason.
Regen happens at higher revs than a fast idle.
It's the cooling fan.

I found it hard to believe too, and I was there!

This was a petrol engine, in a Fiat car, in the 80's.

 

[HeidiF]

Apologies to you as this may seem like a really daft question too... Did you go for the 5 year old Hymer, or another vehicle. ???

Happy New Van

Cheers
Red.

Sorry, thought I’d replied earlier, but yes we did get it! All very exciting if a bit daunting...

 

[Reallyretired]

Early cars did not have a water pump and relied on convection to circulate the water. I suppose it may happen to a certain extent in a modern engine.

 

[OG1]

Thank you, thank you! Melt down averted

You would think the Dealer would explain everything, regarding your purchase. They have your money that’s the end to it all, they just don’t know.

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[Guigsy]

I've not heard my fan stay on after I'd pulled the key until the other day. It's surprisingly loud. And it does stay on for a couple of minutes.

 

[Wildbill]

Usually when that happens on a diesel it's a run away .....
It will rev higher and higher until it destroys itself but that only happens if the engine is so worn it can draw oil from the sump via worn bores, worn valve stem oil seals or more likely badly worn turbo oil seals.

Watch to the end

Wrag in the intake usually stops them
Bill

 

[Lazyboy]

Most probably the electric fan for the radiator.

 

[Johnthebike50]

I wonder what the logic is behind this, as surely it will only cool the water that's ensconced in the radiator at switch off, as the water pump won't be running to circulate it around the cooling system ?

Thermal syphon, hot rises cold falls,
Not at a fast rate, hence a pump when running, when the water is cooled enough the switch will stop the fan automatically.
my old Velocette motorbike depends on thremo syphon system, no pump used.

 

[pappajohn]

When the engine gets too hot particles in the cylinder glow red hot and even with the ignition off fuel will be ignited and detonate! This is not good as the shock waves can damage mechanical parts!

With the ignition turned off there is no fuel to ignite as the pump is also off.

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[pappajohn]

Talking about air con I have a 2007 fiat Ducato and was wondering if it is possible to fit air con in the cab

It is but it will be extremely expensive and not worth it.
Major wiring, plumbing, altered dashboard and, of course, the Aircon unit, compressor and radiator.
I fitted a couple of 6" 12v fans at the ends of the dashboard.

 

[bigwood]

Never mind noisy cooling fans it would be the traction pixies screening for mercy if I did more than 60 in my Series 3 Landrover Diesel. Either that or something falling off because of the vibrations.

 

[RYHALLRED]

When the engine gets too hot particles in the cylinder glow red hot and even with the ignition off fuel will be ignited and detonate! This is not good as the shock waves can damage mechanical parts!

Fuel injection used on modern Petrol & Diesel engines don't suffer from this as the fuel is cut off when ignition is shut off. Only old fashioned carbs or maybe early petrol injection had the dreaded run on.

 

[RYHALLRED]

Usually when that happens on a diesel it's a run away .....
It will rev higher and higher until it destroys itself but that only happens if the engine is so worn it can draw oil from the sump via worn bores, worn valve stem oil seals or more likely badly worn turbo oil seals.

Watch to the end

Or if you are silly like me and pour redex into the intake system to clean it, nothing much happening, no exhaust smoke, so I then rev a little. The pooled up redex then got pulled into the engine & it screamed. I jumped into the driver seat, put the car into first gear, foot on the brake & dropped the clutch. Engine saved & a lesson learned.

 

[Reallyretired]

Many years ago I had a Highwayman on an old Daf chassis. The engine was very agricultural and due to a short in the starter wiring it restarted as soon as the engine was stopped even with the key removed. The early diesels did not need an electrical supply to run mechanical fuel and diesel pumps.

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[RYHALLRED]

Just one other little point about fans & pumps. Its common in modern petrol cars with a turbo, to have a water pump run after the engine is switched off to cool it, its usually reasonably quiet in operation. This may also be the case with a diesel turbo, but i'm not to sure.

So even when you think everything is turned off via the ignition key, our fossil drinking friends can still be alive and making noises

 

[L' Hobo]

Just one other little point about fans & pumps. Its common in modern petrol cars with a turbo, to have a water pump run after the engine is switched off to cool it, its usually reasonably quiet in operation. This may also be the case with a diesel turbo, but i'm not to sure.

So even when you think everything is turned off via the ignition key, our fossil drinking friends can still be alive and making noises

I even have a water cooling overrun pump on my 1989 VW T25 TD Westy so, perhaps, not that unusual on a turbo Diesel?

 

[Bramidan]

Sounds very much like it's trying to complete an unfinished DPF regeneration.

Our Ducato (2021, 2.3, 140hp, Euro 6d) does this occasionally. The description "roaring sound" is very accurate. Much louder than normal electric cooling fan noise. It's louder and more urgent sounding than normal engine tickover noise. Typically scenario is where we've pulled up and stopped at services after a long run. It's loud enough for other people to give it a quizzical look, especially if you've locked up and left the van. Typically lasts for about 5 minutes. You can sense and smell accompanying heat being generated.

My 2022 Ducato did this yesterday and you could smell it, I actually thought I might have overheated to the extent I got back in to check the temp gauge
Just an ancillary question, I have the 9 speed auto and I usually select eco because I thought it would be more economical, I do know about DPF regeneration, to a small extent but do you think I should run it on the other settings and if so at what intervals?

 

[dash300]

Another vote for a Regen occuing if it is a roaring fan sound. Usually accompanied by a hot smell. Usually not noticed as it occurs whilst driving but occasionally on getting to a location and switching if the regen is still going on the front end sounds like its about to take off!

 

[68c]

My 2022 Ducato did this yesterday and you could smell it, I actually thought I might have overheated to the extent I got back in to check the temp gauge
Just an ancillary question, I have the 9 speed auto and I usually select eco because I thought it would be more economical, I do know about DPF regeneration, to a small extent but do you think I should run it on the other settings and if so at what intervals?

I remember a fire engine turning up to put out a burning combine harvester, the first thing they did was to spray water under their vehicle in case their exhaust set light to the straw under it. Perhaps worth keeping in mind if you are parked on dry grass with a hot exhaust as the DPF cleaning can get very hot.

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[Fdhadi]

When I worked on cars in the late 70’s, if the timing was out they would be known to “run on”.

Like jockaneezer, my FS1E “Fizzy” did the same