Wow, you guys get great fuel mileage. My Series-60 equipped '02 Wanderlodge gets 7 to 7.25 mpg after 110K miles. It weighs 48000 lbs and I pull a 4000 lb toad.
What final drive ratio do you guys run? My bus runs a 4.78:1.
My operating temps are similar to what everyone else here sees. The S60 thermostat is a Weir design. It starts to open at 190 deg F and is fully open at 205 deg F. My fan is hydraulically powered similar to your Newells. The fan comes on full speed at 200 deg F and stays on till the coolant temps drop to 190 deg F or for three minutes - this is all under the control of the DDEC IV ECM.
When climbing a grade under full power say in 100 deg F (OAT, Outside Air Temp), the coolant temps will ramp up from 190 deg to something less than 205 deg F as the thermostats fully open and the fan comes on full speed. At some OAT, say greater than 100 deg F, the tstats will be fully open and the fan will be on full speed and the coolant temps will be 205 deg F. As OATs further increase any remaining coolant system capacity will be depleted and the coolant temps will increase with increases in OAT. At 212 deg coolant temperature, DD says I'm entering the realm over overheating. As OAT's continue to increase, then at 220 deg F the DDEC reduces power.
The coolant temp sensor is located at the back of the cylinder head adjacent to cylinder number 6. The hottest part of the engine would be the upper cylinder liners the piston crowns and the upper combustion chambers. It's easy to see that while we may read 212 deg F at the coolant sensor, the coolant temp at the cylinder liners and the upper combustion chambers will be quite a bit higher. We can have the onset of nucleate boiling in these areas even if the coolant temp sensor is reading within spec, especially if the condition of the coolant system is slightly degraded; hence, DD's overheating spec of 212 deg F and de-power at 220 deg F. It's easy to see that at 220 deg F at the sensor you can have 230 deg F or more at the liner and combustion chambers. If there's a faulty radiator cap, or scaling, or if you're at altitude, then you can have boiling in these parts of the engine. So even though 50/50 ethylene glycol won't boil till 260 deg F or so (with a 10 psi cap), DD built in a safety margin for fouled coolant systems, out of spec coolant, or scaled engine coolant passages. Anyway that's my take on it. Please correct me if I'm wrong.
The way I operate my bus is I don't let it get above 205 deg F. The S60 will run at 205 deg F all day. I watch the coolant temps closely but I also pay attention to the exhaust gas temperatures. I don't let the EGT's get above 1000 deg F. I pretty much drive the bus according to the EGT's.
David Brady
'02 Blue Bird, Wanderlodge LXi
Series 60
NC