odd oil pressure issue
 

2010 KW T660 with Cummins ISX with 98k miles and about 19k miles on the oil.

Just recently I have noticed the oil pressure slowly dropping from 35-38 pounds down to 21-25 pounds over the course of about 45 minutes to an hour of steady highway driving. If I stop and shut the truck off for 2-3 minutes and start it back up I get the oil pressure back to 35-38 pounds and start the whole process over again.

I also notice that if I am climbing hills while it is at the low pressure end it will drop a little more and then, when the fan kicks on to cool the water, it will regain a few pounds but never gets above 28 pounds pressure.

One more piece of info....the oil temp will remain between 225 and 230ish while the water temp remains in the 180 degree range other than when climbing hills.

I'm thinking oil pressure sensor. What do y'all think? :confused:

Most likely,....but since it's still under warranty, i'd drop by the dealer, and make them do a complete check up...

I would suspect the oil sensor in an engine as new as yours. It's not usually too expensive and is easy to change.

There are some other things that can cause a drop in oil pressure though but not usually in an engine under 100,000 miles.

The first thing that comes to mind is a broken piston oiler. They are a plastic tapered tube that directs engine oil from the main oil galley to the bottom of the pistons for cooling. If it breaks off, the hole is larger so it passes more oil causing a loss of pressure. It also causes the piston to run hot because it is no longer getting oil to cool it so it can do some damage.

Another thing that I have seen happen in a Cummins engine is one of the crank shaft thrust washers falling out. This will also cause a loss of oil pressure and can do some damage to the crank shaft and engine block.

Neither of these issues should be found in an engine as new as yours but they are possible so I thought I would mention them.

oil pressure drop
 

Try a new oil filter. That's an easy and inexpensive place to start eliminating, and the oil does not need to be changed to do so. If that helps even if for just a short period of time it may indicate contaminants in the oil. If it doesn't help you can move on to the other possibilities.

I would start with an oil change. If a filter gets a bit clogged it can cause your oil pressure to drop. Besides, at 19,000 miles on your oil it is past time when I usually change my oil. Regular oil changes can prolong engine life.

not only that. but can prolong turbo & water pump life too. I have always changed my oil at 10,000 miles. about 4 times in the last 11 years I have went to 12,000. that may be one of the reasons why I have over 1.3 mi miles & still original turbo & all gear train components are original & had been checked, in good condition. back years ago the oil was a lot cheaper, but still, oil is cheaper than a over haul. I have heard that cummins has low oil pressure compared to others. at 19,000 miles I would expect the oil to be a lot lower pressure than when it has only a few thousand on it. I notice a difference in mine when I change it & when it has 8-9 grand on it. also if the temp outside is real hot like in the 90's oil pressure will be lower.

Thanks for the responses.

This is a company truck and they let the oil go to 25k miles before change.

I was just trying to get an idea of what it might be so I can pass the info along to our service dept.

Filters could be an issue. I wouldn't worry about a 25k mile oil change interval, since that within the OEM recommended interval on the ISX. I have been doing 25k oil changes since I got my '06 with an ISX and have had good looking oil samples with recommendation that I could go longer. I have, except a couple of times, have only used Donaldson filters throughout. My samples still look as good as ever and the engine now has 589,000 miles on it. I did my previous N-14 at 30,000 mile oil changes and it went to around 1.4 million without a major problem and averaged around 7mpg its whole life. Wish I still had that engine. Though it may have happened somewhere, I have never seen an engine fail or major parts come apart on engines that have done 20,000 mile or more intervals in the last 20 years. None of the fleets I have been associated with have had a problem with these longer intervals ( and some of those fleets held onto their trucks unlike the big boys that trade all the time). Most all of their problems were from the drivers, not the oil change interval, except for the occasional lemon engine, that it wouldn't matter if you changed the oil every 1000 miles, it would still crap out.

I would target the gauge first, then the sensor. Reason, if the sensor was sending low oil pressures, then the ECM would be throwing fault codes and maybe even taking the engine to shutdown. Since you didn't mention that problem, then the gauge would be my first choice. That is one of the nice things about having something like the Cummins RoadRelay display on the truck. It will show the oil pressure the sensor is sending and then you can compare that to the gauge.

...first question; what engine oil?

You need to verify that 'actual' oil pressure matches gauge display.

any final updates
 

My 2011 T660 is doing the exact same thing . Did you ever figure out what it was ?