This I couldn't resist, partly because I didn't know the answer. But I do know how to use a match, so it wasn't too hard to figure this out. Brake fluid does burn. DOT3, DOT4, and DOT5 all burn, and all about the same. It's not an explosive fast burn like gasoline, but a slower burn like vegetable oil, or a bit faster than candle wax. You might be hard pressed to light a puddle of the stuff with a match, but give it a wick or a sufficient heat source to get it started and it will then continue to burn almost as well as fuel oil. That was a fun experiment. Thanks for the challenge (but don't let your mother catch you doing it).

At 02:51 AM 5/17/02 -0400, Steve Shoyer wrote:
>.... stepped on the brakes pretty firmly. The pedal acted normally for a moment, then sunk to the floor. .... The fire engine .... did the trick. ....
>
>.... if you aren't too squeamish: www.shoyer.com/mgb/fire!.htm
>
>1) How could a fault in the brake system cause a fire? I'm assuming that something burst and was spraying fluid in the engine bay.

Wow! There was a lot of heat in there. I was thinking it must have been a gasoline fire before I tried a little brake fluid. Now I suppose it could have been either one.

I was checking the pictures to figure out the plumbing and what model year it was in order to know what gadgets we were dealing with. Then I noticed the twin carbon canisters (1979-1980 model MGB) and took another look at your signature line to verify it. The 1980 MGB also has one of those notorious plastic fuel cut-off valves right next to the brake booster. This cut-off valve is supposed to be a safety device, used in concert with the inertia switch in case of an accident, but when the aging plastic valve breaks in the right way it can spray gasoline directly onto the exhaust manifold. However, that does not appear to be the case here.

The clue is that the paint is not badly singed in the carburetor side of the engine bay, and the water and fuel hoses there appear to be in fairly good condition (considering). The fire was much more severe on the distributor side of the engine bay, and the air cleaners appear to be burned on the top but not much on the bottom. This I take to indicate that most of the fire was on the distributor side and was likely lapping over the top of the engine to burn the air cleaners and the one side of the plastic brake fluid reservoir near the air cleaners more that the other side of the reservoir.

Also consider how thoroughly the wiring harness was burned, and the position of the hottest spot on the bonnet, and it appears that the file was centered on the distributor side of the engine. Next thought was fuel overflow from the carbs through the vent hose to overflow at the carbon canister, but the canisters do not appear to be so badly burned either. So that got me down to thinking about brake fluid from a burst hose at the right front wheel, but I suppose that would cause more fire under the fender than is obvious, and that's pretty far away from the heat sources around the engine, especially being on the opposite side of the engine bay from the exhaust system.

The hottest point of the fire appears to be on the inner fender just aft of the ignition coil. In the later stages of the fire the insulation from the wire harness may have been a major source of the fuel for the final hot burn. Or there may have been some rubber and/or oil there from the oil pressure sender unit flex line (hard to say with that much heat and I can't tell from the pictures). But that doesn't mean it started as an electrical fire, only that it was centered near the right side inner fender.

Getting back to your mention of the suddenly flat brake pedal before the fire was noticeable, I would concur with your first speculation that it was a burst brake line that started some of the brake fluid on fire. Someone please tell me the physical location of the connection of the RF brake hose to the steel line, if this in inside or outside of the inner fender, or maybe below the bottom edge of the inner fender (I don't have an MGB handy for inspection). Otherwise it may also be possible that the steel brake line to the RF wheel broke somewhere inside of the inner fender. Brake fluid under high pressure spraying around the engine bay from the right side could reach across the engine bay to hit the exhaust system to get the fire started. I figure it had to hit the exhaust system as it takes a pretty hot heat source to cause spontaneous combustion of brake fluid. After that the bulk of the fire would go to the location of the bulk of the fuel, which may have been a continuing slow leakage of brake fluid from a broken line near the RF inner fender. So how's that for an educated guess?

And then Steve said:
>2) What do I need to do to get it repaired?

Oh man, I don't know if you will repair this one. The restoration work may be more costly than the value of the car. You would ultimately have to strip and repaint the body (and repaint the engine) and replace the wiring harness and all of the rubber hoses and fuse block and relays and anything else made of plastic or rubber.

>Is the engine usually junk after a fire?

Actually no. If it isn't left to set for too long before repairs, you can usually clean and repaint the engine, replace the wiring and all of the plastic and rubber bits, replace some gaskets and seals, change the engine oil and start it up again. It takes an awful lot of heat for a long time to cook the innards of an engine, so that's probably just paint and gaskets and seals being damaged. The bulk of the mechanical part of the engine is probably still in reasonably decent condition.

>They put a lot of water behind the dash, and the instruments are pretty foggy.

You may have to remove the front lense from the instruments to let them dry out, and best not to wait too long before this is done. I can see how badly the wiring was burned in the engine bay, but was it also burned under the dash? And was it hot enough to start the carpet on fire behind the firewall or on the front tunnel area?

>3) What is the best way to deal with the insurance company? I have a regular policy on the car (low mileage discount, that's about it).

Here's hoping and assuming that your insurance includes comprehensive coverage. I would guess they will want to call it a total and write you a check, hopefully sufficient to buy another similar car (minus the deductible amount). If you don't have agreed value coverage it will ultimately be up to you to prove the value of the car before the fire (if there is any disagreement with the claims adjuster). If you were so inclined you could negotiate with the insurance company to retain the car (for a parts car) for the same price as its salvage value (which is not much to the insurance company). Unless this car is a really fond family member, I wouldn't get to attached to the idea of restoring it, as that looks like quite an expensive proposition.

Six months later, after the damage had been repaired and repainted, plastic parts and wiring harness replaced, the cause of the fire was discovered. The brake pipe to the front left wheel had a small pinhole that was spraying brake fluid into the engine compartment. It sprayed a mist of brake fluid onto the carbs and exhaust manifold (and everything else in the engine compartment), and something ignited it. This eventually spread to the plastic coating on the wiring harness and the plastic parts, melting them and making a big mess. In addition to the expired brake pipe, the engine also had a blown head gasket (most likely a result of the fire).