If your engine temp is around 150 F you will get have cylinder wash the diesel isn't able to combust properly so fuel runs down the cylinder wall into the crankcase. So with my truck that defuels doesn't burn the fuel that way other does ,since it was new. I took a 24x24" mudflap and cut it to fit under the engine it starts just under the rad it is tied up with the 500 lb string 1/8" The other thing to do is i suspend between the hood supports is to hand the 8 inch baler belting inbetween them varing the width with the temp out side. at -40 C there is just several inches showing or open rad. The engine temp should be at about 170*F and I figure that it should be good . I have idled the truck at -27C and the engine temp is just fine when cooler it is able to have the exhaust brake applied. You want to keep the engine oil warm enough. Also if you are able to part the truck so wind is coming from the side is good as well. I have driven the truck at -23 C and the engine really sounds different without these additions to it! The cylinders sound like they are bang bang etc.