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mechanic36 (Automotive) (OP)
18 Mar 02 18:28
Hi all!  Any mechanics out there ever heard of an engine oil leak from the rocker cover gasket onto the exhaust manifold causing an under bonnet fire?  Many thanks!
evelrod (Automotive)
18 Mar 02 19:58
Yer darn skippy!!!  If the leak is big enough it can burn that sucker to the ground!  (Been there , done that. 350 Chevy C-250,  summer ,1981)


Rod
ivymike (Mechanical)
18 Mar 02 21:53
Guess it all depends on luck- I had a gas leak onto the exh manifold that probably went on for 30 minutes before I noticed it (driving down the highway).  I pulled over immediately when I finally smelled the leak strongly enough to worry about it, and fixed the hose.  I let the thing sit for a good 45 mins to evaporate some of the puddles of gas, and then I went on my merry way...  :)

MaxRaceSoftware (Automotive)
19 Mar 02 2:37
Ford had a problem with 460 cid
and front mounted distributors
along with a 2 inch long rubber gas line hose going to AuoLite 4-barrell carb...over time , sometimes
rubber hose cracked and sprayed fuel on distributor cap

Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers
http://www.mindspring.com/~meauxracing/

TheBlacksmith (Mechanical)
19 Mar 02 10:25
The navy used to teach the fire triangle;
Air+fuel+ignition=fire.

Any flammable liquid leak, oil, gas or ATF can cause a fire under the hood, the air and ignition (hot metal) is already present.  All depends on luck.

I piloted a boat about 3 miles into port at 1000 RPM with a blown Holley accelerator pump diaphram after wiping up the gas all over the intake manifold.  Everyone was in life jackets, my wife has holding a fire extinguisher and I was in VHF radio contact with the Coast Guard.  Like they say, "I am a trained professional, do not try this at home."

Blacksmith


buzzp (Electrical)
19 Mar 02 15:43
Im no mechanic but this happened to me as well. Burned the car to the ground. That was the first one. The second one was when I was very young and had the air cleaner off. The car backfired through the carb and sparked a fire. It must of caught something close by on fire and that was all she wrote. I did get this fire out without a total loss.
mechanic36 (Automotive) (OP)
19 Mar 02 17:59
Thanks to all of you who've taken time to reply to my post.  Having read through some previous posts (on unrelated automotive topics), I now realize that my question was a little vague.

To ivymike, MaxRaceSoftware and TheBlacksmith, I too know of cases where people have been lucky when a gas leak spills on the exhaust or HT system and cases where they haven't.

Evelrod, thanks for your reply.  Can I ask if that was a race or road car?  (higher temp exhaust I'd guess for a race car)  Also, in all your years of engine building and racing, is that the only case you know of?

buzzp, your second case happened to a buddy of mine - he wasn't quick enough to put the fire out and the car was wrecked!  In the first case you mentioned, was that an engine oil leak that did the damage?  Most relevant to the current question (see later), did your insurers pay out?

Ok.  Now to phrase the question a little more specifically (and scientifically).  A buddy of mine had an underbonnet fire which wrecked his car back in Nov 2000.  His insurers claim that the fire was caused by a leak from the rocker cover gasket onto the exhaust manifold and that, as he couldn't provide service records, they weren't going to pay him.

I've spoken with a guy who was in the fire service for 24 years who claims that the leak alone couldn't cause the fire.  To help my friend out, I'm trying to find out if it is (scientifically) possible for the leak to cause the fire.

Here's the results of my investigations so far:  the flash point of oil (which I think means the temp at which it will ignite IF provided with a spark - please correct me if I'm wrong) is around 200 degrees centigrade.  Below that temp, you can heat it up and wave sparklers near it and it'll be ok (compare with gas, which at room temp will go BOOM when the spark ignites the fumes).

I measured the temp of a friends ex manifold (a diesel taxi) and it turned out to be 55 deg C - admittedly, the car hadn't got to full operating temp.

Hope the above clarifies my question.  Once again, thanks to all who've helped out.
evelrod (Automotive)
19 Mar 02 22:05
mechanic36---The truck that burned was a 1981 Chevy C-250 chassis cab ( fairly new company truck) and had the rear portion of the right rocker box gasket blow out.  The exhaust manifold was probably red hot from the freeway and when we stopped to gas up, poof, up she went. We saved the truck, but the engine was history! It is DEFINATELY possible, to burn down an engine due to an  oil leak!

Race car headers generally operate in the dull red-straw orange zone  approx. 1200 to 1400 degrees F.

No this is my second personal experience with an engine fire.  The first was in 1959 in my brother-in-law's Ford coupe with an Olds engine.  The stock GLASS fuel bowl on the stock fuel pump (lower right corner near motor mount) broke and we stalled out.  In order to get us home , I decided to disconnect the fuel line and fill a beer can with gas.  Next,  open hood , climb on fender and DRIBBLE fuel into carb. Mixture control leaving a bit to the hap-hazard side, carb spit back---ME?  Exit stage rignt---ENGINE?  Well, I think you get my drift!


Rod
TheBlacksmith (Mechanical)
20 Mar 02 7:47
You're right - the three stages in order are;

Vapor point - temp where vapors form, for gas about -30or lower.

Flash point - temp where fuel will ignite in the presence of an ignition source.

Auto ignition point - fuel will combust on its own - this is analogous to what happens in a diesel engine.

As for insurers, they're in the business to make money, not give it away - I personally know of no vehicle make that requires tightening of or replacement of valve cover gaskets, so what do the service records have to do with the validity of his claim?


Blacksmith
Whittey (Automotive)
20 Mar 02 16:29
Generally when you see flames dripping after a car wreck that is engine oil.


-=Whittey=-
mechanic36 (Automotive) (OP)
20 Mar 02 17:41
TheBlacksmith - the insurers claim that if the vehicle had been regularly serviced at the appropriate intervals, any slight leaks on the rocker cover gasket would have been detected and reported or rectified.  They claim that the substantial leak was sufficient to cause the fire.  Having not seen the vehicle, I can't say how bad the damage was; all I know is that the main dealers quoted around 4000 GBP and as the vehicle was only worth 6000 GBP, they wrote it off.

Steve
buzzp (Electrical)
20 Mar 02 17:48
My insurance did not pay for the oil leak situation because I only had liability on the car. So I can't say if they would of paid or not. We had a 97 bonneville burn to the ground in our driveway. The wife was driving and smelled smoke, turned around called me at work to ask what to do, I told her to call fire dept then try to unhook battery. i seen the pretty black smoke on my way home and new what it was. The fire dept didn't pinpoint the cause and the insurance company paid for the car. Me, fires, and cars don't get along.
Rob45 (Automotive)
1 May 02 12:26
I can assure you that oil leaking onto an exhaust manifold can even cause an engine fire in a Diesel,  if the engine is being run hard.
The reason you only measured 55C (= 131F) on that Diesel taxi manifold is that it was idling,  and there's  no exhaust temperature to speak of in a Diesel at idle. It's mostly just an air pump.

Regarding your friend's engine fire: the insurers are probably right.

Worst car for this was the old Pontiac Fiero with "Iron Duke" 4-cylinder engine.  To fit that engine into the space available, they fitted it with a 3-quart oilpan, under which ran the catalytic perverter.  When folks didn't check the oil often enough (like, daily!)  the resulting engine failure caused a hole in the side of the block, from which engine oil ran onto the hot converter, catching fire, etc.
Guest (Visitor)
3 May 02 8:42
Mechanic36,

Rest assured that oil WILL catch fire on a hot exhaust manifold.
The insurance company is correct in claiming negligence on your friends part, but I would still dispute not paying.  They are in the business of protecting us from ourselves.  Many, many accidents are caused by negligence and lack of maintenance...poor brakes, split fuel lines, poor handling due to bad shocks, etc., eating while driving, and on and on.  The vast majority of claims are due to our own stupidity!  Unless there was intent to defraud, they should pay up.  They may want to refuse any future poilicies, but they did take your friend on as a customer, and that was their call.  

As a side note with a slightly different circumstance...a lot of Chrysler turbo cars burned to the ground due to oil leaks on the turbo and pipes near it.   I know of several that occured well AFTER the cars were shut off and the turbo was quite cool, but obviously not cool enough.

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