Motoring Discussion > Why do cars catch fire? Miscellaneous
Thread Author: SteelSpark Replies: 31

 Why do cars catch fire? - SteelSpark
Drove past a car on the hard shoulder of the M11 today, which was well ablaze. Not sure what the make was, but looked a few years old.

The driver seemed to be OK, and was talking on his mobile on the roadside. Road was pretty obscured by smoke, and there was a tanker stopped on the hard shoulder about 100m before the car.

Just made me wonder. What is it that can make a car catch fire?
 Why do cars catch fire? - Zero
Fuel leaks and electrical failure are the two commonest causes.
 Why do cars catch fire? - Skoda
post deleted at Skoda's request
Last edited by: VxFan on Sun 21 Aug 11 at 00:02
 Why do cars catch fire? - mikeyb
Saw a 3 series on fire a couple of weeks back, Thgink it was only about 5 weeks old - it pulled over after going through a set of lights with a bit of smoke coming from underneath, but as I drove past you could see the flames licking under the engine bay (driver got straight out and was on the grass verge). Drove back past half hour later and there wasnt much left being hooked up on the recovery truck
 Why do cars catch fire? - swiss tony
>> Fuel leaks and electrical failure are the two commonest causes.
>>
Car fires are more common than in the past, and are likely to get even more common.

In the past, petrol cars had low pressure fuel systems, that often had engine driven fuel pump, that stopped pumping when the engine stopped (mechanical pumps, some did have electric pumps)

With the introduction of fuel injection electric pumps took over, and the fuel pressure increased.

The latest breed of injection systems have increased fuel pressure again, to the level that joints are one use only, ie fuel pipes must be replaced once they have been disconnected, as a perfect seal can only be guaranteed once.
This is unlikely to happen in the real world..
 Why do cars catch fire? - zookeeper
is it possible to ignite petrol with a lit cigarette? ive heard it cant be done
 Why do cars catch fire? - swiss tony
you cannot light petrol.
petrol vapour however is extremely flammable.
 Why do cars catch fire? - spamcan61
>> >> Fuel leaks and electrical failure are the two commonest causes.
>> >>
>> Car fires are more common than in the past, and are likely to get even
>> more common.
>>
Combine the increased fuel pressure with the increasing amount of permanently powered up electrics and it's surprising we don't see more fires.
 Why do cars catch fire? - Zero
I do 12-14k miles a year. I probably see on average about 2 cars either on fire/being put out/recent burned out shell every year.

I doubt you can do 10 miles down any motorway without seeing scorched hard shoulder. On the m3 round here it send to set the heaths on fire as well.

Its a miracle so few people are hurt.
Last edited by: Zero on Mon 22 Aug 11 at 14:36
 Why do cars catch fire? - swiss tony
>> I doubt you can do 10 miles down any motorway without seeing scorched hard shoulder.
>> On the m3 round here it send to set the heaths on fire as well.
>>
A couple of years ago I was cruising up the M40 from High Wycombe to Coventry, trying to keep the fuel consumption down.
To stop me getting bored at 60ish, I was counting the scorch marks on the hard shoulder.....
I lost count at around 25.. (around 90 miles)
 Why do cars catch fire? - Manatee
>>What is it that can make a car catch fire?

Discarded fag ends. Imagine one with a 70mph draught on it stuck in a bit of bonnet insulation or even an air filter; or lodged in some of the oily cack that inhabits some engine bays. It doesn't have to get through the radiator, it can swirl up from below. I wouldn't be surprised if 50% of fires are so caused, considering the zillions chucked out - the chances seem likely to be higher than winning the lottery jackpot, and somebody does that just about every week.
Last edited by: Manatee on Sat 20 Aug 11 at 19:37
 Why do cars catch fire? - devonite
An angry missus smouldering in the passenger seat!
 Why do cars catch fire? - Zero

>> cack that inhabits some engine bays. It doesn't have to get through the radiator, it
>> can swirl up from below. I wouldn't be surprised if 50% of fires are so
>> caused, considering the zillions chucked out - the chances seem likely to be higher

I would put discarded fags down as less than 0.05% causal
 Why do cars catch fire? - DP
The Ferrari 458 Italia had a problem with the rear wheelarch lining coming adrift, rubbing on the wheel and going up in flames. Rather a worrying number of them went up in smoke until Ferrari recalled them. The fix, I am reliably informed, was a dozen self tapping screws! :-)
 Why do cars catch fire? - rtj70
DP the problem on the Ferrari was the wheel arch lining was glued on and that was the cause of the problem. As you say screws were used to fix the problem.
Last edited by: rtj70 on Sat 20 Aug 11 at 20:50
 Why do cars catch fire? - swiss tony
>> I would put discarded fags down as less than 0.05% causal
>>
I agree.
I also stand by my (and Zero's) reasons.
Last edited by: swiss tony on Sat 20 Aug 11 at 20:16
 Why do cars catch fire? - Injection Doc
yep mostly electrical, lots related to back up heater systems which use very high current and lines of glow plugs in a water tube !
Chaffed wires in looms, wires trapped under dash boards from new build ! very common and eventually burn. Fuel leaks from high pressure joints and so much plastic trim under the bonnets !
 Why do cars catch fire? - Manatee
>> I would put discarded fags down as less than 0.05% causal

You could be right of course - but it's guesswork. If 1 in 10,000,000 caused a problem, that would be a good few fires. Why favour other causes when you have millions of sources of ignition lobbed at following traffic everyday?

I'm sticking with me fags.
 Why do cars catch fire? - VxFan
I remember pulling into the services on the way back from Alton Towers quite a few years ago. Pulled up next to a Sierra in the car park, and one of my passengers noticed steam coming from under the bonnet of it. Er, it wasn't steam and the paint on the bonnet was starting to blister. I quickly moved to another parking spot just as someone came running across with an extinguisher. They smashed the radiator grill and inserted the nozzle through the hole to douse the flames. Found out afterwards they did this so as not to open the bonnet and feed the fire with oxygen. At the time I didn't know things like that, but having had fire training at work, as well as being fire warden for the building I'm in, I do now.

Anyway, shortly afterwards the fire brigade turned up. They said the Sierra was quite a common car to catch fire after they'd been on a long run. Heat soak from the engine could cause the plastic air filter ducting that hung over the top of the engine from the air filter housing to the exhaust manifold to droop with the heat from the rocker cover. If there was enough heat present then it ignited the plastic ducting. Apart from the usual electric and fuel related fires, this was quite a common one too.
 Why do cars catch fire? - rtj70
Sometimes smoke/steam can help in other ways. I had just had a Vectra serviced and went with a colleague to collect him after dropping a car off for a service.

When we got back and stopped there was a chemical/plastic smell coming from the engine bay... Reading Dave's post we shouldn't have (but did) open the bonnet and then I called the RAC/AA.

They found a hose melted and leaking liquid. We were sure water. Hose temporarily replaced.

Set off from home... smoke and a smell from under the car! Got towed to the dealer.

Cause? Plastic bag on the exhaust :-) Spotting the melted water pipe leaking water was the bonus.
 Why do cars catch fire? - Iffy
...Plastic bag on the exhaust :-)...

I had what turned out to be the same on my Cortina estate as I was driving along a dual carriageway.

I was aware of smoke and fumes, looking in the rear view mirror, I noticed a small blob of smouldering plastic drop onto the road.

Decided to accelerate and blatted along at 70mph+ for a few miles in the hope the rest of the bag would melt/drop/blow off.

It did.

Going back to Dave's post about opening the bonnet, I believe a few householders have been injured by a whoomph of flame after opening the door to a burning room.

 Why do cars catch fire? - Lygonos
As Rattle has previously mentioned the high average IQ of forum visitors I assume everyone knows not to put water onto chip pan fires....

youtu.be/InYVTuRzgX8

Worth a watch even if you know not to do it ;-)

 Why do cars catch fire? - Robin O'Reliant

>> I would put discarded fags down as less than 0.05% causal
>>

Borne out by the fact that whereas the number of smokers has halved in the last 25 years the once rare instance of car fires continues to rise in number
 Why do cars catch fire? - bathtub tom
I've seen two car fires. The first was caused by an electrical short under the rear passenger seat - I suspect modern materials are less flammable.
The other was brake fluid leaking onto the exhaust - highly flammable stuff brake fluid!
 Why do cars catch fire? - rtj70
Every now and then you see one on the motorway. More recently a big cause has been rioting.

For those driving for a few decades... is the problem better, worse or the same these days. I can only really comment on say 17 years driving. And it's very rare from what I have seen.

... so my new car will probably burn out due to faulty tyre pressure sensors in a few weeks :-)
 Why do cars catch fire? - henry k
I have seen just one car on fire a renault Fuego and that was a few years ago.
The fire brigade were there. The bonnet was up and the engine was burning bright.
I think it was the head that was burning but the heat was causing the dash plastic to melt and gently drip into the foot well.
The lads were hosing the road underneath and were letting it burn.
IIRC they said the powder they had on board might not extinguish it
 Why do cars catch fire? - Lygonos
Seen 3.

VW Passat 1978 T-reg- fuel line leaking onto exhaust.

VW Scirroco 1988 E-reg - think electrical problem

Reliant Scimitar GTE (age unknown) - electrics then body on fire.
 Why do cars catch fire? - oilburner
Last time I saw a car on fire it was a Mitsi Evo on the hard shoulder of the M5. Quite a fireball it was. From what I could see of the remaining part of the car, it had been modded quite a bit...

The owner looked absolutely gutted, as you can imagine.

Oh, and I saw the aftermath of a fire from a youngsters Renault Clio, the pavement it was parked on was badly damaged, leaving a small crater behind!
Last edited by: oilburner on Mon 22 Aug 11 at 14:15
 Why do cars catch fire? - Iffy
A friend of mine turned on the heated seats on his Volvo and became aware of smoke coming from underneath him.

He then remembered where he'd stuffed his last McDonald's bag and wrapper.

 Why do cars catch fire? - bathtub tom
That reminds me, although I'm sure I've posted it before.

Many years ago, brother-in-law came to visit on a wet Sunday in his 300. He complained his wipers weren't working. I found a fuse blown (10A IIRC) that promptly blew again when replaced. In the absence of a handbook or anything else, I roughly measured the current draw at around 20A. I fitted a 20A fuse that held and after a suitable period of time without smelling any smoke, I told him to get it checked out at a garage when he got home.

A couple of weeks later he furiously blamed me because driving in the outside lane of a dual carriageway, the partial short-circuit in the heated driver's seat burnt a hole in the seat, trouser and nether regions and you can't stand up in those circumstances.

Alanovic, are you reading this?
 Why do cars catch fire? - Alanovich
>> Alanovic, are you reading this?
>>

*Nods slowly with slightly lopsided grin*
 Why do cars catch fire? - Bagpuss
There was a recall for the Peugeot 307 some years ago due to some of them catching fire following a short circuit on the power steering pump (I think this was only a problem with LHD models).

In the recall letter Peugeot advised owners not to leave children or dogs unattended in the car until the recall work had been carried out. What a horrifying thought.
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