Why do cars just catch fire on their own...?

[AJMD429]

Last night when my wife got home, she remarked that there was a 'strange sound coming from the house next door' and I went outside to listen. It sounded just like a small generator or air compressor running, so we ignored it and got ready for bed. Maybe 20 minutes later there is a loud 'bang' which I assumed was the generator backfiring (mine ALWAYS does when I shut it off), but I figured I'd take another listen. En route to the balcony I see out the window what looks like the side of the house on fire, so I tell my wife to call the fire department, while I rouse my son and we run next door to see if the guy is ok, and the house too (since we own it). Turns out the CAR was on fire, and though it was parked almost underneath the balcony, my son's spraying water on it until the fire department kept it from igniting (places he wasn't hitting often enough with the water were having the sap boil out of the wood).



So. . . neighbor says the car is (was) a 2000 BMW that he got used a few months ago, and it has functioned perfectly, and was running just fine on the way home. He got home, turned the car off, and went inside to get ready for bed. I don't know if he heard the 'generator' kind of noise or not - he may have been in the shower or something. I guess much of the engine or transmission contains magnesium, so even after the car was so far gone you could spray water into the trunk and nothing stopped it before it hit the front bumper, the area where the engine and transmission used to be was still white-hot and wouldn't go out.

I've read before about cars just catching fire like that, but always wondered what in heck happens.

What is fortunate is that the garage-door doesn't work well, so tenants usually don't park inside the garage, which is underneath the livingroom in the ALL REDWOOD house.

[Chuck 100 yd]

Sorry to hear that!
I worked for a John Deere dealership that had a tractor catch fire in the middle of the night and burned the dealership to the ground.
At another tractor dealership ,I worked for many years ago, They had a tractor that would start itself up and was left in gear one day. It started up and drove out into the middle of a divided highway and died because the fuel was shut off. Luckily nobody hit it or was injured by it.
Modern cars have so much electrical gadgets I often wonder why it don`t happen more often.

[jeepnik]

Not sure about BMW's but some cars have electric fans that continue to run after the auto is turned off. This may have been what you heard. And, if so, it's possible the electric motor on the fan shorted out and started the fire.

Eons ago I went on a run for a brand new convertible (red and supposedly had white interior, don't remember the model) that was fully engulfed. Power seat had shorted out while being driven. When the driver (just back for SEA) felt his backside getting hot he parked it and climbed out. Saw the smoke and called us.

[3leggedturtle]

Glad no one was hurt. Watched the Fire Dept. try to put out a car fire. The battery cable got rubbed raw and shorted out. They would put the fire out, and 1-2 minutes later it would overheat and flare up. This went on for 1/2 hour til they finally got the hood open and cut the cables. Luckily it was on the street with no low hanging trees around.

[Grizz]

there are roughly 230 million handy dandy mobile ieds on the roads today, some of them go younger than others

glad no one was injured by that one

[wecsoger]

felt his backside getting hot

That's funny. Guy I know had a Mercedes SUV (obviously had more money than I do) burnt his...well tush when the seat thermostat malfunctioned. Offered to show me, but I passed. (grin)

Two things. Most people think that when you turn the key off, you turn the car off. It is not truly off till you disconnect the battery posts and set the battery off onto the workbench. There's still a lot of electrical things going on otherwise. If something fails, say the fan switch thermostat, that little guy might fire up and run till it melts.

As far as the Beemer, sounds like it was 'dieseling' after the owner shut it off. If there's fuel problems, and enough heat in the engine compartment, it's just like cooking off a round in an auto weapon.

Is there that much magnesium used in the BMW's? If so, once that catches, you are so done for. In many meanings of the word. I don't think many civilian fire departments have anything to deal with fires like that, other than back up and contain.

Something else to look forward to - the new electric cars with the lithium-ion batteries. Those guys are just static fire bombs in-waiting. Destroy parts of the matrix separating internals, once a short starts going there's a thermal runaway with spectacular results. If it's not your car. Boeing found that out on the 787's.

[Old Ironsights]

What wescoger said.

Looking at that pic, the burn pattern does not indicate (to me) that the fire initiated under the hood... so it is unlikely that the Fan Motor was the culprit.

The interior, and particularly the Drivers Seat is GONE.

I've been to enough car fires to suggest/agree that that that was the "seat" (ha ha) of the fire.

The backfire noise was probably an airbag going off.

[Old Ironsights]

Glad no one was hurt. Watched the Fire Dept. try to put out a car fire. The battery cable got rubbed raw and shorted out. They would put the fire out, and 1-2 minutes later it would overheat and flare up. This went on for 1/2 hour til they finally got the hood open and cut the cables. Luckily it was on the street with no low hanging trees around.

They need some retraining.

That's the FIRST thing we do after getting the fire knocked down.

Open the hood and cut the power.

[3leggedturtle]

They tried, it took the 1/2 hour to get hood open. Was a '73 Dart Sport. Happened in April of '86. They really struggled to get it open. Finally 2 of them with a big long pipe ripped and pried it open.

[Old Ironsights]

They tried, it took the 1/2 hour to get hood open. Was a '73 Dart Sport. Happened in April of '86. They really struggled to get it open. Finally 2 of them with a big long pipe ripped and pried it open.

Oh.. OK. If we have that much trouble we break out the K12 saw and cut it apart. Didn't have those in the 80s.

[Rusty]

When I was a LEO back in the 70's our local FD had a standard policy when ever they showed up the first thing they did was cut the battery cables.

Glad no one was hurt Doc.

[El Chivo]

It's because cars, like guns, are evil.

[vancelw]

Modern cars have so much electrical gadgets I often wonder why it don`t happen more often.

That!
Cars don't burn accidentally nearly as much as they used to, now that everything is fuel injected. Carburetors and rubber fuel lines were major culprits. But the more electronic stuff there is (like heated seats, air compressors, . . .) the more likely something is to fail.

We used to average a car fire a day, now it seems like its one every six months, not counting ex-girlfriends who found out the hard way they were exes-and they know the Molotov recipe.

[AJMD429]

It just seems strange that one part catches fire (like a seat-adjustment motor) then it spreads through a car to engulf everything. I can understand that once the gasoline tank ruptures everything would go, but before then it seems like it should be easy to design cars that won't continue to burn just because a seat motor or whatnot burns out. Of course enough heat and sparks to get something like a big chunk of magnesium burning and then you're screwed I guess.

[J Miller]

Seats are made from fabric ( usually a synthetic ) and foam. That stuff is very flammable and burns pretty fast and hot. Much of modern vehicles is synthetic, or plastic. That is why once it starts it spreads quickly. Which is not really surprising considering the confined area the heat has to work with.

Glad there was no injuries and no housing damage.

Joe

[cas]

I've had electrical "fires" in three vehicles, two were just wires burning up in the dash while driving and didn't turn into a big deal. One in a 1950's chevy, the other a 1980's Mack. Not fun.

The third however was a 1980's Ford van that burned up well and good on it's own, sitting in a parking lot. It was a total loss. I believe it was a pretty common issue and something Ford dragged it's feet on, ignored and avoided a recall on because I've seen about 6 of them burt or burning myself. So it couldn't have been all that uncommon.

[44-40 Willy]

Is there that much magnesium used in the BMW's? If so, once that catches, you are so done for. In many meanings of the word. I don't think many civilian fire departments have anything to deal with fires like that, other than back up and contain.

Magnesium fire on a Navy ship and we'd try to jettison the stuff overboard. I don't think there is any putting it out.

The third however was a 1980's Ford van that burned up well and good on it's own, sitting in a parking lot. It was a total loss. I believe it was a pretty common issue and something Ford dragged it's feet on, ignored and avoided a recall on because I've seen about 6 of them burt or burning myself. So it couldn't have been all that uncommon.

My sister in law had a late 80s Bronco II burn up in her driveway. She drove it home, parked it and about two hours later it was extra crispy. They never did figure out why it burned.

[gamekeeper]

I had a wire burn out on a motor cycle I was riding, seeing smoke coming from under my gas tank made me stop and get off pretty quick.. disconnected the battery before any flames appeared..

[Old Ironsights]

Is there that much magnesium used in the BMW's? If so, once that catches, you are so done for. In many meanings of the word. I don't think many civilian fire departments have anything to deal with fires like that, other than back up and contain.

Magnesium fire on a Navy ship and we'd try to jettison the stuff overboard. I don't think there is any putting it out.

You have to have "Class D" extinguisher compound... and it has to be used ONLY on the metal... so it's not very good for a car fire.

There are several Class D fire extinguisher agents available; some will handle multiple types of metals, others will not.

Sodium Chloride (Super-D, Met-L-X or METAL.FIRE.XTNGSHR) contains sodium chloride salt, which melts to form an oxygen-excluding crust over the metal. Useful on most alkali metals including sodium and potassium, and other metals including magnesium, titanium, aluminum, and zirconium.

Copper based (Copper Powder Navy125S) developed by the U.S. Navy in the 70s for hard-to-control lithium and lithium-alloy fires. Powder smothers and acts as a heat sink to dissipate heat, but also forms a copper-lithium alloy on the surface which is non-combustible and cuts off the oxygen supply. Will cling to a vertical surface-lithium only.

Graphite based (G-Plus, G-1, Lith-X, Pyromet or METAL.FIRE.XTNGSHR) contains dry graphite that smothers burning metals. First type developed, designed for magnesium, works on other metals as well. Unlike sodium chloride powder extinguishers, the graphite powder fire extinguishers can be used on very hot burning metal fires such as lithium, but unlike copper powder extinguishers will not stick to and extinguish flowing or vertical lithium fires. Like copper extinguishers, the graphite powder acts as a heat sink as well as smothering the metal fire.

Sodium carbonate based (Na-X) used where stainless steel piping and equipment could be damaged by sodium chloride based agents to control sodium, potassium, and sodium-potassium alloy fires. Limited use on other metals. Smothers and forms a crust.

Some water based suppressants may be used on certain class D fires, such as burning titanium and magnesium. Examples include the Fire Blockade and FireAde brands of suppressant. Some metals, such as elemental Lithium, will react explosively with water, therefore water-based chemicals should never be used on such fires due to the possibility of a violent reaction.

Most Class D extinguishers will have a special low velocity nozzle or discharge wand to gently apply the agent in large volumes to avoid disrupting any finely divided burning materials. Agents are also available in bulk and can be applied with a scoop or shovel.

RE: Some water based suppressants may be used on certain class D fires, such as burning titanium and magnesium. Examples include the Fire Blockade and FireAde brands of suppressant.

Very pricey. Most small Depts can't afford the stuff. We use LOTS of AFFF Foam... mainly because of the fuel/oils, but it does a fair job of smothering metal too.

[Sixgun]

If its a Beemer, the usual cause is late payments.

[J Miller]

The 80s and 90s Ford problem was a defective design in the ignition switch. Even with the switch turned off it would overheat and ignite. I was working at an auto parts shop when this info was finally released. We could not stock enough aftermarket switches for the vehicles. Ford as you say drug their feet redesigning their switch. Standard and Borg Warner changed the design at the start of their production.

Joe

[Panzercat]

I'd wager some sort of electrical short. Melts some insulation, sets it or something close to it on fire... My Pops had his back trailer hitch light connections short out and it was smoldering all the way down the road. Wouldn't have known it either until some other guy pulled up next to us noting the whispy smoke. Pulled over to the side of the road and the entire inside of the hitch was a black mess.

[bdhold]

my '84 alfa caught fire once when a plastic bag on the road was sucked up onto the exhaust header.
It only burned a little of the foam insulation off the firewall - I had an extinguisher handy.

[Old Ironsights]

The 80s and 90s Ford problem was a defective design in the ignition switch. Even with the switch turned off it would overheat and ignite. I was working at an auto parts shop when this info was finally released. We could not stock enough aftermarket switches for the vehicles. Ford as you say drug their feet redesigning their switch. Standard and Borg Warner changed the design at the start of their production.

Joe

Hmmm

Lost a 97 mercury tracer to a dash wiring harness meltdown. No actual fire but lots of smoke.)

Totalled it. (Replacing the dash electricals cost more than the car..)

[Jmay]

Generally cars catch fire due to a direct short it gets hot and catches fire. Sometimes a fluid leak you don't realize you have can drip on hot exhaust manifolds and catch fire after you have parked. I work for the City OF Dallas as a mechanic in the same garage the garbage trucks get serviced and they catch fire a lot cause folks dump hot coals in trash and then trash truck pics up the trash an catch fire. Gets interesting when one is an alternative fuel trash truck with natural gas tanks strapped all over it and starts to blaze!

[J Miller]

Some years ago in Phoenix I saw a smoking garbage truck pull into a vacant lot, and dump his load. Lots of smoke until the load cleared the truck then it went up in flames.

Interesting to watch.

Joe

[rogn]

Parked, shut off and sitting still fires are almost by definition electrical in origin. The parts of a car that arent metallic are flammable. Wire scuffing is common, as is damage by maintenance work or little furry creatures. I guess its remarkable we see fewer fires than we do. Oh, the application of the "heavy duty" fuse helps in some cases. My memory of my years in that industry was that more fires were encountered in parked cars than while driven. May just have been the market.

[piller]

Used to have an 89 Honda Civic Si that would get electrical shorts at least once a week. The wiring harness was coated with a very soft insulating plastic and it would rub off and short something out. I finally had to purchase an aftermarket one and have it installed. I have never owned a Honda since. Oh, the dealership told me that nothing was wrong when I showed them that you could signal for a right turn and the fuse would pop and put out the turn signal and the dash board.

[Canuck Bob]

If its a Beemer, the usual cause is late payments.

Seemed to cause a lot of fire when I was a kid!

[1894]

My neighbors car went up in flames this morning .
I had never seen a car fire before , lots of flames and smoke .

[Sixgun]

My neighbors car went up in flames this morning .
I had never seen a car fire before , lots of flames and smoke .

Yea, its amazing. A guy's car at work caught fire (started under the hood) and like, in no time, the entire car was engulfed in flames. 20 minutes later the only thing left was the steel. --------------6

[jeepnik]

My neighbors car went up in flames this morning .
I had never seen a car fire before , lots of flames and smoke .

Yea, its amazing. A guy's car at work caught fire (started under the hood) and like, in no time, the entire car was engulfed in flames. 20 minutes later the only thing left was the steel. --------------6

Hmm, wonder why they call it a firewall? I doesn't seem to keep the fire in the engine compartment.

One of the peskiest burns I ever got was from windshield glass that blew out of a Siat (Spanish made Fiat). The didn't have safety glass and when the interior over pressured it blew out, cut thru my turnout and got lodged against my right tricep area.

[K1500]

This is why I do not like to park in an attached garage...well, that and an attached garage makes a great shop when not cluttered up by cars.

[AJMD429]

This is why I do not like to park in an attached garage...well, that and an attached garage makes a great shop when not cluttered up by cars.

Dude down the road a ways had a garage maybe 20 feet from the main house, both metal-roofed, but attached by a brick 'breezeway' or whatever you call it (top half almost all windows, just a hallway about 15-20 feet long). It was an older structure with a garage too-small-for-a-big-suv, so he built a separate vehicle garage, built a small concrete-block room in it to house his wood furnace, and used the rest of the garage for firewood storage. He had two overhead 'sprinklers' hooked up like in a commercial building. The small furnace-room acted as a 'jacket' for a blower that put the heated air to the house via a foot-diameter insulated duct running through the breezeway, and the cold-air return was via louvers in the lower portions of the door at the house end of the hallway and the same type (metal) louvered door on the furnace room itself.

I think if his furnace went 'nuke' due to creosote, or even if his firewood stored indoors like that, had caught fire, his house would have been ok. It sure made 'fetching firewood' less of a big deal in the winter...!