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Oil pressure related issue

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Jon Wells:
I've been trying to get ahold of Dave Atherton about an issue we have with our Cat C9 engine (2006 Monterey, 400HP C9).  While driving to the Michigan Upper Peninsula, the engine light started to flash.  [The engine light flashed a bit while driving through Milwaukee the previous day, but then it was fine.]  At first it would only last about 20 seconds and the power was very dimminished.  I was looking at my Alladin engine information screen, and noticed that the oil pressure was going doing weird things.  It would jump around showing 10, 0, 15 PSI, and then it would show 87, the engine light would go out and the coach would be running fine.  I made it to the Iron Mountain Walmart, checked the oil level, and added about 3 quarts.  We stayed there long enough to have a bite to eat so it had a chance to cool down.  Then, we resumed our journey.  I had to pull over about 3 more times.  The first 2 times, I kept needing to put oil in.  All together, I put in about 6 quarts.  The last time my check engine light came on and I stopped, the oil level was fine.  We were about 8 miles from the campground and were able to make it.  Thoughts???  There's a Fabick Cat about 2 hours from hear in Marquette MI.  I may need to call them and hopefully they can work on motorhomes with Cat engines.
I should mention that the week before all this oil pressure stuff, we had to deal with an issue with our hydraulic fluid for the power steering (and radiator fan).  As we were approaching Nashville, my engine light started flashing.  My steering started feeling stiff and I pulled over.  I discovered that the filter for my power steering / radiator fans was rather loose, and the ATF had emptied, spraying our towed Ram truck.  I tightened the filter and added ATF (and went to a truck wash).  We also stopped at the nearby TA truck stop, and was surprised to learn that they do not carry ATF.  At this point I only had one gallon of ATF in the reservoir, and I limped over to the nearest Walmart.

Gayden.Peel:
A few things that would make it easier to start to narrow in on the issue would be:
1. Obvious new oil drips on block or around the engine
2. Any wetness around the vent tube or aft of the tube like on the chassis
3. Any noticeable smoke on start-up or while running / underload

CAT does allow for some oil consumption, and I think 250hrs for changes. Your 6 gallons in a single trip seems excessive, however. How many total hours on the engine? Also what oil are you running right now?

Jon Wells:
I have looked for leaks.  The radiator fluid seems fine.  The oil on the dip stick seems fine.  I was thinking of getting my endoscope out to take a look in the areas I cannot see from the rear or from the top hatches in our bedroom.  I'm embarrassed to say that I had not checked the oil level since I had the oil changed back in March.  The oil they used was Amzoil (I do not remember which product).  My exhaust has not been smoky.  I read somewhere that there are two sending units, one for the dash gauge, and one for the ECM?  How do I know which is which?

Thank you,
Jon Wells

Eric Maclean Co-Admin:
Jon
Maybe this will help
You should be able to verify oil pressure between the engine ECM oil pressure sensor and the gauge sending unit
To see if they both agree.

https://youtube.com/shorts/4mPEDNkjMh4?si=Wbqrd0trabSc34Hb

You need to verify the oil pressure with a master gauge to make sure that there is no issue mechanically with the engine first.

The Cat engines have a engine oil cooler built into the water jacket on the side of the engine block in this oil cooler there is often a oil pressure relief valve arrangement that can sometimes go bad causing erratic oil pressure.

However that would not account for oil lose or consumption.
There are several areas where the engine can consume oil

1) turbo charger ( may have a bad seal allowing oil into the compressor housing and into the intake where it is consumed by the engine.
 To check this remove the lower charge air cooler connecting hose at the charge air cooler and look for oil with the mount of oil missing it should be obvious.

2) check the coolant for oil in the surge tank or radiator ( oil will float on the coolant and create a milkshake consistency)
This would be evidence of a bad oil cooler also check the oil for signs of antifreeze.

3)  check for excessive blow by at the draft tube when the engine is hot and under a load

4) look for oil leaks

5 ) make sure the oil filter is tight and make sure that who ever did the oil change did not leave the old seal ring in there as two oil sealing rings will allow one to move and create an large oil leak under pressure.

It's also a possibility that the oil change was never done properly and that the engine was simply low on oil
Either way don't operate the engine when the oil pressure goes south as major engine (bearing and crankshaft  ) damage can take place very quickly a matter of 10 to 20 seconds .
 

Gayden.Peel:
I agree on don't drive or idle with bad oil pressure, but since he already drove it presumably hundreds of miles on his trip and the gauge was all over the place even reading extremely high, I was going with some sort of electrical issue / sender is malfunctioning. Otherwise with 0-10PSI his coach would have stopped running a while ago.

On the ACERT C9 I think they all had compound turbos, I was wrong, the C9 ACERT for motorhomes only had a single turbo, you could pull the charge tube and inspect for any oily residue on the impellers. Also check for shaft play by grabbing the impeller and giving it a wiggle, it should not move. If the hot side was leaking then you would likely seem some buildup of oil on the exhaust tip or some smoke out the rear underload. Older HEUI injection systems could cross contaminate thru the injector seals, later ACERT C9s use common rail with electric injectors so it's not going in that way Also it looks like even in the later ACERT engines they still had a HEUI in motorhomes it would have been much later C9.3 versions with Common Rail. Top oil consumption on C9s would be Turbos or Rings / valve guides, but I really doubt the rings would be worn out, this isn't a long-haul trucker with 500K miles. adding some additional info I was given, It looks like there are some people saying that changing the thermostat out to a higher temp can help to seat rings better, that the lower temp thermostats wouldn't allow the engine to get to proper operating temp. Might be something to discuss with your mechanic or do some research on also. Again CAT says excessive oil consumption is "Oil loss of 1 gallon every 40–50 hours or 2,500 miles" your described loss of 6 quarts over a single trip I think is much higher than this.

Without a clear understanding of where the oil started before the trip, again assuming it's been some time since your last oil change, and you have driven the coach before this trip) it's going to be hard to really understand just how extreme the consumption was. Assuming that when you topped off the engine it was perfectly full, you said it ended up needed several more "gallons" not quarts right? Gallons in a single sub 100hr trip should produce something visible, either as burnt and into smoke, or leaks on or around the engine. I'm an idiot and wet back to verify I saw gallons, you said quarts, so I'm sorry. Still 6 quarts in your trip is excessive but not near the extent I thought I read, I just couldn't believe that it was that many gallons :) I would really look at the vent tube and see if you can notice any excessive blow-by (smoke and pressure or even oil particles) discharging.

If it was mine I would do an oil change and inspect the oil for signs of engine wear (if it looks like it just left the strip club then maybe see a professional) otherwise if the oil and filters look clean (invest in a filter cutter so you can look at the filter pleats) Or if you have it changed at a shop have them check it out. Without starting a debate on oil I'd say get the bog-standard Cat oil (Cat DEO-ULS 10W-30) and run it next, just to get a baseline. With the explained gallons of oil loss you've got to be able to see it somewhere.

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