Eddie,
As I recall, it was on the opposite side of the engine from the exhaust, but it was a high-pressure line that sprayed the entire engine compartment with fluid. When he opened the engine cover, everything inside it looked like it was on fire. According to the insurance investigator, the part that burst was one of those rubber hoses sheathed in a metal braid. (I've always called them Aeroquip hoses -- but I realize that is just a brand name). These flexible lines came off the pumps and connected to steel lines on the frame that ran toward the front of the machine. I think their purpose was to shield the main, metal lines from the vibration of the engine.
There was only a little fire extinguisher in the cab, and it slowed the down, but not before it had burned other lines, dumping more hydraulic fluid underneath the machine. There were literally puddles of burning hydraulid fluid underneath the machine. We were afraid it would catch the diesel fuel on fire and he'd just filled it that morning -- 200 gallons I think was the capacity.
I don't think it was the heat of the brushfire, for sure, because we'd just gotten it started -- he hadn't been working more than 30 minutes (max) when this happened. He was also operating it with the cab door open, so he was sensitive to the heat. At the time the operator noticed smoke, he actually had the boom out toward the fire, so the engine compartment was quite a ways away from the fire. He rotated the excavator almost parallel to the brushpile, before losing all pressure, then shut the engine down, and jumped out with the fire extinguisher in hand. But, he'd left it with the engine compartment pointed almost directly downhill, and it kept leaking fluid... gravity???
He emptied the fire extinguisher and while it smothered some of the flames, the burning oil underneath it kept reigniting the leaking fluid. He yelled at me to run and start the water pump, which I did, and by the time I got it started and back to the site (about 500 feet), he'd gotten the engine fire out but we still had to deal with all the fluid that had dumped onto the ground. I'm not sure how much fluid it held, but I'd guess at least 50 gallons -- it could've been far more. And, of course, water is almost worthless fighting an oil fire... but after it stopped draining out of the excavator, we were finally able to put the fire out underneath the machine, mostly by just flooding it, but the fluid that had run downhill from it kept burning. Then, we took turns for the next 2-1/2 hours or so, standing on a track, keeping the excavator wet down to cool it, so the diesel tank wouldn't catch fire, while also keeping the now-blazing brushpile fire from getting close enough to reignite anything.
I got no pictures while all this was going on, but here's the scene from the next morning, after we'd gotten the excavator out of the way...
The tracks you see are where the little Komatsu dozer was spinning in the muddy mess we'd made, trying to push the disabled excavator out of the way... when it died, it locked the treads, and it had to be literally drug uphill away from the area... They brought a mechanic the next morning, and he had to remove a gear from each of the drive motors to get the tracks to "free-wheel" so they could then load it with the other excavator and dozer...
I spent the nite onsite, just keeping an eye on things, and the fire in the brushpile burned down. With my typical luck, they wouldn't issue me a burn permit for that second day (too dry and windy), so I ended up running the pump again, completely putting the fire out in the brushpile, and later paid about $5K to get it ground up with a tub grinder...
It wasn't exactly a small brushpile...
Sorry about the thread-jack....