1997 M1078 Oil pressure drop after 20 minutes of driving

[5_Ton]

I have searched threads here as well as the gone through the TMs. At start up I get 45 PSI solid every time. After driving for about 10 to 20 minutes the pressure drops to 15 to 20. No red light stop light any ideas suggestions. I have ordered a new pressure switch. And thought to next connect a manual pressure gauge.

Thank you in advance.

 

[GeneralDisorder]

45 is pretty low at startup. Most people report 80+ on cold start. There's a current thread right now by a member with a 2001 A1 3126 truck that had VERY similar oil pressure and his oil pump housing was broken. The 3116, 3126, and C7 all use the same pump and CAT redesigned it like 4 times apparently. A 3116 is going to have the older gear style pump that's known for issues. Start reading this thread at this post, and watch the YouTube video I posted from a guy with one of these engines in an RV with the same problem:

Mav’s M1088A1 Conversion

yeah just gonna see if I can get a copy printed off on base, these should have a USAF T.O. as well and vehicle maintenance should have access if they can... print it to Thumb drive. so you have the files and can share them. Would help sooooooo many people. That is assuming the files are of...

www.steelsoldiers.com

 

[Mullaney]

I have searched threads here as well as the gone through the TMs. At start up I get 45 PSI solid every time. After driving for about 10 to 20 minutes the pressure drops to 15 to 20. No red light stop light any ideas suggestions. I have ordered a new pressure switch. And thought to next connect a manual pressure gauge.

Thank you in advance.

.
Military gauges are notoriously inaccurate.
What about attaching a real mechanical gauge to the motor and let's see what you really have?

Maybe shoot a few pictures and post them here so we can see what sort of power plant you have?

.

 

[RRaulston]

In the thread GeneralDisorder sent you to, I posted a chart for oil pressure. Yea, not a fan of those numbers. I might be doing a pump in the next few weeks.

 

[Ronmar]

Yep, connect a mechanical oil pressure gauge and confirm. There are usually unused ports on the oil manifold down where the gauge sender and OP switch are connected on the left side of the engine just forward of the starter. You didn't mention which truck engine this is happening on…

 

[5_Ton]

Yep, connect a mechanical oil pressure gauge and confirm. There are usually unused ports on the oil manifold down where the gauge sender and OP switch are connected on the left side of the engine just forward of the starter. You didn't mention which truck engine this is happening on…

My apologies its the 3116 11k miles. Starts instantly no smoke idles smooth, engine oil cleaner than any diesel than I have ever seen. No outward indications of issues. Ill take some pics and a video of operation today and repost for more clarification.

FYI Big thanks to Ronmar your video on "Deleting front glad hands" allowed me to trouble shoot why my park and service brakes were not operating correctly. It was the 2 way check valve right before the emergency glad hand so clogged with crap it was not working. Now all brakes work perfect.