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RSCTRANS · 03-09-2017, **(Subject: CM 871 low oil pressure - where to start? )**

2010 international lone star with Cummins CM 871. Earlier today I noticed my oil pressure gauge drop down to about 25 psi under load. 504,000 miles on the engine. Within the last six months I have been reading and performing all of the maintenance on my motor, that I have learned on this site. I did a forced regen a week ago and the differential pressure reading came back at .50. I was very happy. I have even went as far as buying an auxiliary power unit and had it installed two weeks ago. This way I do not idle my engine at night. Six months ago there was a crank case pressure issue. I put in a new air compressor, that did not take care of the problem. Then I replaced the turbo. That seems to have corrected the issue at that time. However, about an hour ago my check engine light came on and then it went into shutdown mode shortly after. I carry the Cummins insite program with me. It once again read high crank case pressure. I took the shortcut for today so I could make it home about two hours away, and drilled a quarter inch hole in the crankcase filter cover facing the driver on the top. However, I am concerned that I have something else going on. Where should I start? Oil filter? Gauge? Sensor? Oil pump? Or could it be internal? Please advise and any suggestions are greatly appreciated. Thank you in advance. As a sidenote – I have a boost gauge that is reading between 25 and 30 psi when turbo is kicking in pulling the hills. I have a 10 speed transmission with 373 rears. That's how the truck came to me when I purchased it used with 300,000 miles on it. I have been trying to keep it around 1450 rpm's to 1500 rpm's for better fuel consumption. Again, any advice is greatly appreciated.

Hammerhead · 03-09-2017, **(Subject: CM 871 low oil pressure - where to start? )**

(03-09-2017 )RSCTRANS Wrote: 2010 international lone star with Cummins CM 871. Earlier today I noticed my oil pressure gauge drop down to about 25 psi under load. 504,000 miles on the engine. Within the last six months I have been reading and performing all of the maintenance on my motor, that I have learned on this site. I did a forced regen a week ago and the differential pressure reading came back at .50. I was very happy. I have even went as far as buying an auxiliary power unit and had it installed two weeks ago. This way I do not idle my engine at night. Six months ago there was a crank case pressure issue. I put in a new air compressor, that did not take care of the problem. Then I replaced the turbo. That seems to have corrected the issue at that time. However, about an hour ago my check engine light came on and then it went into shutdown mode shortly after. I carry the Cummins insite program with me. It once again read high crank case pressure. I took the shortcut for today so I could make it home about two hours away, and drilled a quarter inch hole in the crankcase filter cover facing the driver on the top. However, I am concerned that I have something else going on. Where should I start? Oil filter? Gauge? Sensor? Oil pump? Or could it be internal? Please advise and any suggestions are greatly appreciated. Thank you in advance. As a sidenote – I have a boost gauge that is reading between 25 and 30 psi when turbo is kicking in pulling the hills. I have a 10 speed transmission with 373 rears. That's how the truck came to me when I purchased it used with 300,000 miles on it. I have been trying to keep it around 1450 rpm's to 1500 rpm's for better fuel consumption. Again, any advice is greatly appreciated.

Please tell me I did NOT just read that correctly! You DO NOT drill the crankcase filter cover, you drill the plastic portion of the crankcase filter!

hhow55 · 03-09-2017, **(Subject: CM 871 low oil pressure - where to start? )**

03-06-2016, (Subject: crank case pressure ) Post: #9
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RE: crank case pressure
If you have crank case pressure issues you have one or more of three things that can cause this. One too much blowby from piston rings. Two aircompressor is pushing pressure into crank case. Three the turbo seal is allowing boost pressure to cross into oil drain which goes into crank case. Rawze has video on how to check blowby with homemade manometer.
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RSCTRANS · 03-09-2017, **(Subject: CM 871 low oil pressure - where to start? )**

Ok - I will replace CC filter cover tomorrow. Sometimes it takes mistakes to actually learn. Sorry!!!!!

Rawze · 03-09-2017, **(Subject: CM 871 low oil pressure - where to start? )**

(03-09-2017 )RSCTRANS Wrote: Ok - I will replace CC filter cover tomorrow. Sometimes it takes mistakes to actually learn. Sorry!!!!!

This thread comes to mind. You need a 1/2" or bigger hole!. !/4" hole is nothing. Some guys even drill 2 or 3 in them.

YES, it is the filter element plastic itself, not the outer cover!.

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25-30 boost is low boost for that engine. Sounds like your DPf may be clogged/cracked and the system not reading it.

i see a de-mandate in its future but it may already be too late. that damage may already be done to the engine. For the life of me why do people wait until the engine is done for before doing something about it.

snailexpress · 03-09-2017, **(Subject: CM 871 low oil pressure - where to start? )**

For what you have posted I would open oil fill cap to check blowby. Second. open the the valve cover to check all camshafts bearings.

RSCTRANS · 03-09-2017, **(Subject: CM 871 low oil pressure - where to start? )**

Where should my boost pressure be at during a pull ?

snailexpress · 03-09-2017, **(Subject: CM 871 low oil pressure - where to start? )**

(03-09-2017 )RSCTRANS Wrote: Where should my boost pressure be at during a pull ?

Usually 33 -35 PSI

Rawze · 03-09-2017, **(Subject: CM 871 low oil pressure - where to start? )**

A healthy CM871 engine has around 36+ psi boost in a hard pull.