Somewhat lightweight but still interesting coverage here:
I was unaware of the cause of this incident.
Cheers,
Earl
Used vehicles have higher risk of fires than new. With new cars a crew member is required to make rounds in the car decks once every four hours, with used cars the procedure is once every two hours for the first 12 hours after loading.
Most fires are due to electrical shorts and with a short, after 12 hours in most cases the battery will be dead. In this case that procedure would have “broken” as the short occurred when brake fluid leaked onto hot wires which could have occurred after the 12 hrs.
I’d be extremely surprised if brake fluid were conductive. However I could easily see it attacking and degrading a connector or insulation over time, leading to a short circuit.
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Hydraulic fluids have very low conductivity. That’s why you have to be careful when pumping it and especially filtering it. It can build up a huge charge.
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From the article:
Brake fluid leaking from the master cylinder reservoir cap had been reported to enter the vehicles’ automatic braking system (ABS) wiring harness electrical connectors, causing short-circuits, melting, and fires,” the NTSB reported. By 2012, the National Highway Traffic Safety Administration knew of at least 260 vehicles that experienced a non-crash related fire.
Most brake fluid is essentially an alcohol rather than an oil – that’s why it so readily attacks various materials. It also takes up water readily, which of course would change its conductivity – but not enough, I think, anywhere near enough to directly cause a short in a 12V system.
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That’s all consistent with it attacking insulating materials.
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medium voltage xformers are immersed in a tank filled with oil. I have personally seen a hydraulic sump filter skid shoot 6 in. sparks off an unbonded hose down stream of the filters. The peckerhead was filled with oil and the insulation was swelling and soggy. It megged >4000MΩ so obviously the oil wouldn’t have been a problem with 12V. I couldn’t count all the peckerheads and JBs I’ve open that were saturated in oil. It is true though that certain oils will degrade certain insulators. Although I’ve never seen brake fluid reservoir that wasn’t made out of plastic(an insulator) so obviously it depends.
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Again, brake fluid is much more active than oil. Taste some sometime, it’s nasty.
Just looked it up: DOT3 and DOT4 brake fluids, the common kind, are mixtures of glycols and glycol ethers. See http://importnut.net/brakefluid.htm
I think the reservoirs are probably made from HDPE – high-density polyethylene, which is fairly resistant stuff.
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Not arguing with you man you’re right just throwing some info out there. I’ve read the recall too bad they didn’t disconnect the batteries on the used vehicles.
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