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+--- Thread: CM 871 low oil pressure - where to start? (/showthread.php?tid=1557)
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RE: CM 871 low oil pressure - where to start? - RSCTRANS - 03-09-2017
Thanks for the normal boost pressure range. I will double check that pressure this weekend. I have a feeling that I have been light footing on the hills not allowing the engine to do what It can do. I have been trying to keep the RPMs under 1500 as a rule to help fuel consumption. It may be hurting me more than helping me on the hills. My next question is this – is there A relationship between High crank case pressure low oil pressure? I am concerned about the low oil pressure. I am nowhere near being a mechanic and I am just learning. At least I was smart enough to stumble across this website a few months ago. Thanks to Rawze
RE: CM 871 low oil pressure - where to start? - Hammerhead - 03-09-2017
Sorry, I got interrupted while starting this reply post. I started with the oil pressure part first and see that everyone else beat me to the punch on the blowby issue so I'll leave this post as only referring to the oil pressure part of the question.
Stock tune or @m*m^2?
First, the simplest of things...oil filter. But if you don't cut it open to see if it's plugged you won't know unless you go driving again, and if that wasn't the problem, your still potentially driving with low oil pressure...
Second, the sending unit tells the ECM oil psi, the ECM tells the cab module, so if Insite tells you low pressure numbers, you still don't know for sure...
Third, if Insite tell you higher psi than the gauge reads, your gauge is most likely hooped...
If Insite and the gauge are the same, then try the sending unit...post 5 of this thread shows their location on an 871 http://rawze.com/forums/showthread.php?tid=1532
If these don't produce results, and you haven't sprung a noticeable leak from the rear flywheel housing (it contains a oil rifle) you're looking internally.
Are the rod and main bearings original?
Overhead, does there appear to be sufficient oil flow inside the rocker cover while its idling?
Verifying and answering this gives a direction of where to go next if these don't rectify it.
RE: CM 871 low oil pressure - where to start? - RSCTRANS - 03-10-2017
I will check things out and keep you posted. Thanks!
RE: CM 871 low oil pressure - where to start? - Magard - 03-10-2017
Do Not! try to keep it under 1500 on a hill. You should be looking for the next lower gear. You've been lugging the crap out of it and it's going to bite you. Lite footed or not.
RE: CM 871 low oil pressure - where to start? - Rawze - 03-10-2017
This whole concept of keeping rpm below 1500 is complete bulls$it pushed onto dumbarsse drivers from the mega-fleets.
Magard is right. ISX will last the longest and work best above 1400 in hard pulls and below 1400 is only for flat ground. Downshift early on hills, bring RPM up to 1700+ and keep it above 1400 when getting into any kind of steep hill.
RE: CM 871 low oil pressure - where to start? - Brock - 03-10-2017
Ok I'll chime in here a little bit. Here's my take on this....
Blowby/Crankcase pressure: You never actually said you have excessive blowby, do you? You said you had a crankcase pressure code.... I had that code, replaced the sensor to no avail then pulled back the wire loom and noticed rubbed through wires 2" from the plug. Cummins sell a pigtail to repair this.
Oil Pressure: If your lucky and don't have the update, the oil bypass valve could be your issue.... here is rawzes video on it.
https://youtu.be/KgQ9s_tmsKA
It fixed my low oil pressure problem. If not then it may be needing a bearing roll before you throw a rod.
Boost: I guess we need to know what your boosting under full load to know if there is a issue or not. When your loaded and climbing a hill, keep it above 1500 and giver snot then let us know the most you hit. If it's lower by a little bit then I would suspect a small boost leak maybe. The blue intake hose has leaked a.little bit EVERY time a mechanic has taken it off.
RE: CM 871 low oil pressure - where to start? - RSCTRANS - 03-10-2017
This is all great information. I certainly appreciate the advise. I do have blowby but not sure if it is excessive. I will be putting together a manometer and checking the engine tomorrow. I will send updates as I check things out.