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oil pressure that changes with engine rpm
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culter
Posted 6/29/2014 23:28 (#3943857)
Subject: oil pressure that changes with engine rpm


s.w. Wi.
John deere 4430 with 6800 hrs. Oil pressure is following rpms.
Is it time for new bearings or just oil pump or both? Oil pressure gauge doesn't have #'s and the needle is not that close to the red zone at idle and looks normal at 1600rpms.
I had a truck that started to do this and started knocking soon afterward.
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saskman
Posted 6/29/2014 23:45 (#3943873 - in reply to #3943857)
Subject: RE: oil pressure that changes with engine rpm


I think most if not all my engines have lower pressure with lower rpm
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Big Ben
Posted 6/29/2014 23:55 (#3943884 - in reply to #3943857)
Subject: RE: oil pressure that changes with engine rpm


Columbia Basin, Ephrata, WA
I wouldn't worry about it. They all do that to some extent, especially old engines. I've got a truck that only makes about 10 psi at hot idle. I told myself the truck isn't worth putting engine work into, so we'd just run it until it dies. That was 8 years ago.
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Franz
Posted 6/29/2014 23:56 (#3943885 - in reply to #3943857)
Subject: RE: oil pressure that changes with engine rpm


Ohio
The oil pump spins slower at a lower rpm which equates to lower pressure. I don't think I've ever seen an engine that didn't fluctuate the oil pressure in relation to engine rpm.
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hog987
Posted 6/30/2014 00:10 (#3943893 - in reply to #3943857)
Subject: RE: oil pressure that changes with engine rpm



Central Alberta
If your too worried about oil pressure just put in a heavier oil into it. But ya they all vary some between idle and full rpm. More as the engine get worn.
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bobcan
Posted 6/30/2014 03:16 (#3943921 - in reply to #3943857)
Subject: RE: oil pressure that changes with engine rpm


SK.. in Frozen Cold Western Canada
If it is a true 'mechanical gauge' it will certainly (or should) react more quickly and perhaps accurately.. and if it is an electronic gauge (sender unit, no oil tube to gauge) then there is some chance of it having a 'damper circuit' in it, much as a Gas Gauge so that the resultant pressure shown is not so 'up and down' as the pressure may well be in real-time!! As others have stated, I am fairly sure the is NO cause for Alarm, as long as no drastic changes over what has been seen in recent past!!
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Hay Hud Ohio
Posted 6/30/2014 04:49 (#3943931 - in reply to #3943857)
Subject: RE: oil pressure that changes with engine rpm



SW Ohio
Have installed several mechanical gauges in place of original on 30 series, especially the ones like 4430 open station that dash cluster does not work at all, mount on right side near the sender port, one has unknown over 12000 hrs with 35 psi hot idle and 50 fast idle, 855 big cam runs 18 hot idle and 42 hot revved, had a NTA 380 that ran 90 hot or cold.
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hillfarmer
Posted 6/30/2014 05:21 (#3943942 - in reply to #3943931)
Subject: RE: oil pressure that changes with engine rpm



855 big cam runs 18 hot idle and 42 hot revved,

If that motor is a pre 1990,I'd throw a25 set of piston coolers in
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coastalBend
Posted 6/30/2014 05:32 (#3943953 - in reply to #3943857)
Subject: RE: oil pressure that changes with engine rpm


south texas
Just put a mechincal gauge on the oil filter housing and see what its doing for a test. Those 30 series gauges are getting a little tired and wiring is brittle. Id say 15-20 at 1000rpm and 35-50 at 2200 and its doing fine.

Edited by coastalBend 6/30/2014 05:32
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Tim602
Posted 6/30/2014 06:37 (#3944009 - in reply to #3943857)
Subject: RE: oil pressure that changes with engine rpm


culter - 6/29/2014 12:28

John deere 4430 with 6800 hrs. Oil pressure is following rpms.
Is it time for new bearings or just oil pump or both? Oil pressure gauge doesn't have #'s and the needle is not that close to the red zone at idle and looks normal at 1600rpms.
I had a truck that started to do this and started knocking soon afterward.


culter I have a 4850 with 14000 hrs on the clock and this started around 8000hrs and its still going strong, all I do now is at idle just bump it up a bit around 1000rpm
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twraska
Posted 6/30/2014 07:31 (#3944080 - in reply to #3943857)
Subject: RE: oil pressure that changes with engine rpm


Wallis, TX

Its not that expensive or difficult to roll a new set of bearings in it.

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Hay Hud Ohio
Posted 6/30/2014 09:17 (#3944214 - in reply to #3943942)
Subject: RE: oil pressure that changes with engine rpm



SW Ohio
It's an 85, about 25000 on a rebuild by a retired Cummins Tech that was on the ground floor of developing this engine, (PP out of PA calls him to solve their problems), All is good with this one, 12 is the minimum required as this series pumps a lot of oil.
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farmdude
Posted 6/30/2014 11:05 (#3944357 - in reply to #3944080)
Subject: RE: oil pressure that changes with engine rpm


I would check the crankshaft bearings. Like the last poster said not to expensive to replace an can save a more expensive repairs later. Have you done oil analysis on this engine before? Gives you a good idea on the wear metals an the condition somewhat off the engine. If there is an excessive blowby the oil aanalysis will let you know. I think 5000 hrs is a good rule off thumb to check the crankshaft bearings.
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culter
Posted 6/30/2014 11:37 (#3944405 - in reply to #3944357)
Subject: This is first season with this tractor.


s.w. Wi.
I changed the oil when I first got it, but haven't done a oil anylysis.
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hillfarmer
Posted 6/30/2014 11:40 (#3944411 - in reply to #3944214)
Subject: RE: oil pressure that changes with engine rpm



Hay Hud Ohio - 6/30/2014 09:17

It's an 85, about 25000 on a rebuild by a retired Cummins Tech that was on the ground floor of developing this engine, (PP out of PA calls him to solve their problems), All is good with this one, 12 is the minimum required as this series pumps a lot of oil.


I have 5 855 's

big cams to the stc in a 89

All idle at 45 to 55 with hot oil
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pupdaddy12003
Posted 6/30/2014 12:31 (#3944497 - in reply to #3943857)
Subject: RE: oil pressure that changes with engine rpm



NW Central Ohio
...most engines are pushing oil through relief valves at pre-set pressures when new. As the pump ages..and the bearings wear, the pressure will drop, and so will the unnecessary pumping. That engine may be just getting to the point where it's pumping exactly what the bearings need to keep them lubricated. I wouldn't worry....like you said, if it starts knocking...that's the time to worry.
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ronm
Posted 6/30/2014 13:32 (#3944599 - in reply to #3943857)
Subject: RE: oil pressure that changes with engine rpm


Fruita CO
Plumb in a good mechanical gauge & check it before you get in a panic...like said above, the dash gauges aren't real durable or reliable...nor is the sender. The oil pump in that engine pumps about 29 gal/min., so even if the pressure's low at idle, it's moving oil...and yeah, w/6800 hr. it may be a good idea to roll in some bearings.
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Bern
Posted 6/30/2014 18:41 (#3945045 - in reply to #3943857)
Subject: RE: oil pressure that changes with engine rpm


Mount Vernon, WA
What you describe is quite normal. Internal engine oil demand is fairly constant, whereas pump output varies with engine speed, hence the variation in pressure. The most important thing is that the pressure is where it should be for both hot idle and working speeds. As a general rule for most engines, 10-15 PSI is a good minimum for hot idle, and 40-60 is good for hot working speeds. Check the Deere manual to be sure though.
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