Oil pressure

[Don and Kathy DuCharme]

Recently, when starting our C9 after it has not been started for several days the check engine light and engine warning light come on after a minute or so. They remain on for a minute or so and then go out. I noticed that the oil pressure was above 100 psi when the lights come on and drops to below 100 psi when the lights go out. Both the dash gauge and the Alladin indicate the high pressure. If the engine is restarted within hours after shut down this does not occur. The oil pressure is around 50 psi after it settles down. Do I have a problem?  If so, what is the probable cause?  Any suggestions will be appreciated.

[Dave Atherton]

Don, that does not sound like a oil sending sensor but a sticky check valve on your oil cooler. There is also a service bulletin for check valve update which consists of a spring and check valve  the location
Check valves on engine oil cooler just behind your engine oil filter base. Note there is one check
valve on the top corner and one at the bottom of engine oil cooler. Need a 20 mm socket to remove
The hex plug. Dave Atherton Retired Cat Mechanic

[Richard Davis]

Don
I don't know what year C9 you have, mine is an '06.  I have always had excessively high oil pressure upon startup with a cold engine.  With some research, I determined that some C9s of that vintage had too small a bypass on the oil pump that caused the high pressure.  My local Cat technician told me that the proper solution was to install the later revision oil pump that was built with larger journals.  But, he went on to say that if I did not want to go to that expense immediately, I could alleviate the problem by switching to synthetic oil.  So, I changed the oil to Rotella T6 5W40 synthetic.  The synthetic oil flows better at colder temperatures.  If your high pressure is just a recent change and has not always happened, it is probably a sticking check valve.  But, an oil change to synthetic 5W40 may clean it up as well.  HEUI engines like clean oil.

Richard   

[Don and Kathy DuCharme]

Thank you Dave and Richard.  It is a recent problem, so probably the check valve. The engine is an 06, and we have a bit over 75000 miles without this problem.

[Neal E Weinmann]

Here’s a picture of the oil pump pressure relief valve shuttle from my C9. Although it was found to be stuck it ended up not being the reason for the CEL (Check Engine Light). In diagnosing, it was found that the CEL was actually triggered by a calculated high exhaust temperature. Both the boost sensor and the barometric pressure sensor returned error codes which caused them to generate an erroneous exhaust temperature calculation and a CEL. Both sensors were replaced and the CEL did not reappear.

Following that repair, I too had the pump replacement conversation with the service advisor after CAT was consulted and recommended replacement due to the known pressure relief valve issue. The oil filter valve was found to be operating correctly, but the gauge, Aladdin and CAT software all saw high oil pressure at startup, so I approved looking at the pump. When the pictured condition was found and merited a pump replacement, I considered it short money for a pragmatic preventative service.

[Mike Shumack]

Looks like you made a smart decision and saved a bunch of money down the road.
Did you have to replace the pump housing too (due to scoring), or just the relief valve?

[Dave Atherton]

Neal, question related to your post on check engine light coming on. Did you ever have a event
Code 173-0 and than 173-11. The reason for this question it related to load condition and rpm
Of engine that will cause high exhaust temperature and extreme exhaust temperatures. The event
Code will trigger check engine light when engine rpm’s under heavy load at 1400 rpms and below
with the Heui pump and engine temperature and engine oil temperatures will increase that will
over time cause a sticking condition of the oil pump relief valve. The Heui pump is mechanical being
driven off front gear train and at 1400 rpm, basic cannot increase engine oil pressure to the injectors
until down shift to lighten load being applied to engine.  Dave Atherton Retired Cat Mechanic

[Neal E Weinmann]

Mike - Complete CAT remanufactured pump was installed.

Dave - your continuing contributions to our community here and to RV owners elsewhere have been noted here many times, and I will echo it once again....THANKS! When my CEL first occurred last November, I called you and left a message seeking advice on how best to proceed. You called me back in short order, reassured me that it was likely nothing that would prevent me from driving the bus, and that the CEL would clear, and it did. Once back home, I scheduled a service appointment and had the issue(s) investigated and as noted, all is now well.

The following codes were listed on repair invoice:

108-3 Barometric Pressure Voltage High, Active, 6 counts
173-11, Very High Exhaust Gas Temperature, Inactive (1 Hour old), 4 counts
102-4, Low Boost Pressure, Inactive (64 Hours old), 93 counts

Hope that list helps better explain what was found.

THANKS AGAIN!!

[Dave Atherton]

Neil, yes all of code listed are related to oil pressure, all are events codes. The 102-4 called
boost pressure sensor and the -4 sends problem to the oil pressure sensor called injection
Actuation Pressure Sensor, next event code 173-11 is a extreme load condition at engine rpms
1400 rpms or lower. Last 108-3 atmosphere pressure sensor voltage high. All of these codes
are break down of engine oil raising temperature and or sticking oil pump relief valve
My suggestion to all owners with Caterpillar C-9 and down do not lug your engine at 1400 rpm’s or
lower because the first event code to trigger panel light will be the 173-0 high  exhaust temp.
if condition and load is not lighten up will trigger the 173-11 extreme exhaust temperatures.
There is no damage occurs within operation of engine and suggest driver to not to lug engine
at 1400 rpm’s or below. Dave Atherton Retired Cat Mechanic