Having done a full delete (about 117,000 miles), I noticed that while removing the EGR tube, there was a noticeably thick diesel greasy soot from the EGR recirculating around 30% to 40% of the exhaust/and sparks through the intake manifold, and there is soot deposited on the inside walls of the intake manifold. Using a screwdriver, I scraped some off and I found it was anywhere from 1/16 to as much as 3/16 inch thick, coating every sq. inch inside the Manifold top and bottom. I would have to assume that is where your fires are starting. (Other then an electrical fire, and/or something getting hot, where is the fire source coming from?), under certain conditions a turbocharger producing full boost at full throttle (even briefly) is moving super High heated air in spite of the aftercooler, and going into a very greasy internally coated intake manifold plus the heat and possible sparks getting through the EGR which it shouldn't but maybe dose on occasions . "Could that be the fuel source?" That kind of greasy soot can and dose burn very hot and something on rare occasions is igniting it, then no more pickup. I did not have an antifreeze internal leak, mine was external on the EGR valve itself, If antifreeze is possible adding to the problem, which is assuming that antifreeze will burn, which I have never heard of before, I would think that antifreeze is not the culprit, but the greasy soot put inside the manifold by the EGR and with a High heat or a glowing ember/spark of some type starting the grease on fire. I have seen this on big truck 4 and 2 stroke diesel engines with a badly worn valves or turbo chargers leaking oil around the turbine shafts and going into a intake or exhaust manifold. At night you could see them pushing fire a foot out the top of the exhausts and the exhaust pipes glowing Red hot. Our big farm tractors exhaust manifolds and turbocharger turbine housings and manifolds would turn white hot, you could see them at night 1/4 mile away. They had a lot of hours on them and were slobbering a little oil. Think about the EGR over time depositing a greasy soot inside the intake manifold especially at a cold start up and just Idling around, it would be worse then leaking turbocharger or wore out valves because it is grease, now you have a fuel source waiting for something to get out of control, burn through and catch the aluminum manifold on fire while the turbocharger adds air velocity to the fire till the engine dies. (try putting out a grease fire in confined space sometime, they get super hot in a short amount of time and are nearly impossible to put out). If you can delete the EGR tube some way as I did, I think your fire problem is solved, stopping the soot/grease build up. keep in mind this is opinion, an educated guess with a little experience with burning grease and aluminum.
