ISX605 high oil temp

[smitty210]

This is on a Motorhome Diesel Pusher, brand new 14k miles. The owner has been plagued with high oil temp alarms and engine shutdown alarms. Here is his latest post from our MH forum. Looking for any thoughts from you guys.

Yesterday, I needed to get from Casa Grande, AZ to Yuma, AZ. This is 180 miles of Arizona flat with a pretty good mountain climb right before you descend down into Yuma. I took everyone's advice and decided to avail myself of the SPEEDCO located about 2 miles from where I was staying at Exit 200 on I-10. As an aside, I got the $25 oil analysis (which I don't know how to interpret at this point) but my charge was $480 for 52 quarts of Rotella (so $455 for the standard oil, lube, and 2 filters (no genny service) that used to run me about $330). Anyhow, 2 hours later, I was on my way to Yuma. You remember that I have been told by Cummins and Spartan to run it like I stole it, and that meant that I simply used it the way that I always use it. I turned the ACC off, turned the Valor TPMS on, and set the cruise for 69 mph (75 mph speed-limit) and off we went. Set my dash so that it always showed me oil temperature.

Over maybe the first 40 miles, the oil temperature gradually increased from cold to 250, and then steadily increase to 259 degrees. And at 259 degrees, the temperature stabilized and then began dropping a little at a time for 10-15 miles until it got down to 248 or 245 and then up and down a little and eventually got down to 239 degrees, and then hovered near there. We stopped at a rest stop for lunch and the engine oil temp never got up much past 255 after lunch and usually in the 240-245 range. That is the way that it ran. No Shut downs, no CELs, and the temp varying by terrain up and down from 240-250 let say.

As I said earlier, there is a pretty good rise right before you go into Yuma on I-8, maybe 1000-1500 feet or more (?) with most trucks down around 35-40 mph. I left the cruise set at 69 and we passed a bunch of trucks in 6th, and then the coach downshifted to 5th and we were down to maybe like 50 and the oil temps started up again (coolant moved from 180 +/- to 183 +/-, and this time, did not stop at 259, but hit 262 at which point I got a CEL (no Shut-down icon) but a CEL (with checkmark). I let the CEL show and at this point foot-fed the diesel but basically kept pouring the juice to it, and we climbed for maybe another 30 seconds to a minute when we crested the hill, and the CEL went off, the oil temp stayed at 262 for ~ a minute and as the CEL went off, oil temp started to fall as we descended the back side of the mountains.

So, its pretty clear that the CEL light comes on if you go past 260 degrees, and my guess is that the oil thermostat open at 259-260 and stays open down to about 240 where it closes or stays open thereafter. If the temp exceeds 260 and the thermostat doesn't open fast enough, then the CEL comes on until the temp falls below 259.

Now, I am sure that is what my engine did and how it was working. Whether that is right or wrong is a matter we are discussing. My sense is that this X15 engine is a very different horse than the 450 ISL. Cummins has been quite sure that this engine runs hotter than other engines in their line and the oil cooler and thermostat are set higher than other Cummins engines. Now, my experience confirms what I have been told, but I dont think this 605 should be throwing any codes even when climbing a mountain so I am going to keep pursuing this whole conundrum. My opinion is that the thermostat should probably open at 250 instead of 260 or the ECM is programmed too tight to the 260 degree opening point. Maybe a rapid rise on a big upgrade leads the thermostat to be late in opening. Not sure. Otherwise, the X15 handles normal Arizona driving just fine, but that mountain CEL makes me intent to keep asking questions.

I will be communicating with Spartan and Cummins again today with this new information and see what they say.
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I have another call into Spartan and Cummins and have sent them a copy of my oil analysis which I will post up here also. They will call me back later today. I now understand that I got a clean bill of health on almost all aspects of the oil analysis, but I got two warnings on the oil analysis by SPEEDCO..... V40C and V100C which appears to be a reading of viscosity of the oil done at 40 degrees Centigrade and also again at 100 degrees centigrade. Haven't figured out if it is too much or little viscosity at this point but that will come next (Im betting on too much). No red line readings on anything.