Oil pressure drop as engine warms?

When I start my TEF 20 cold, oil pressure is at max which is 600 but as the tractor warms it slowly drops down to 100 and then stays there is this normal?
 
Losing oil pressure after warm up is a sign that there is wear in the lubed components of the engine. It also could mean wear in the oil pump or a stuck open oil pressure relief valve. I put a remanufactured engine in our TO-30 in 2001. The oil pressure does not change with rpm changes, hot or cold etc. It stays at 27 psi from idle to max rpm regardless of the ambient temperature and coolant temperature. Eventually there will be enough wear that the oil pressure relief valve won"t be able to control the oil pressure and the you will start to see the variations you are observing. As long as you are at or above the manufacturer"s spec limits for lube oil pressure you"ll be OK. Eventually you"ll have fix the problem.
 
First thing to determine is how old your oil is . Older contaminated oil will thin far more quickly than fresh . As previously mentioned the grade is critical as well .
 

The engine sounds strong and good no unusual sounds. My oil gauge says "oil kpa" so once it has warmed up the pressure drops from 600 to 100 kpa and i'm running gulf western 20w50 oil
 

well my oil pressure does change with the RPM at just over half throttle I get full pressure and throttle pushed all the way up i get about 300 oil kpa pressure cold
 
100 KPA is only 14 psi , sweet nothing, especially for a diesel . My FE 35 petrol runs at 60 psi stinking hot and working hard .Do you have an oil pressure relief valve on the oil filter housing ? This might just need adjustment or it could be missing the all important ball bearing that regulates flow . Screwing it down generally reduces flow and thus increases pressure .
 
Yes I have the valve on the filter housing but I remember someone saying not to adjust it as it can starve the engine of flow? otherwise i would adjust it also so running it with the bad oil pressure is almost like running it with no oil?
 
A oil pressure regulator is a bypass valve, so if you adjust it for higher oil pressure you are making the bypass valve open later making more oil go into the engine (thus it makes the oil pressure higher).
 

Try it and see , it is not difficult and is easy to put back the way it was . The results will be almost instantaneous , just don't go bonkers on it , a few turns with an open ended spanner may be all it needs . The relief valve on the FE35 I mentioned before was all but falling off when I got it , a few turns saw it working well .
A rule of thumb for an engine in good condition , four to seven threads visible on the relief valve body .
 
yrs ago when I worked on engines for a living,56 to about 85 all kinds of gas and diesel engines, if the oil pressure dropped after it was at operating temp, we always dropped the pan and checked the main and rod bearings with plastigauge and tightened the nuts or studs with a torque wrench, usually around .002 clearance. always look on the back of the rod and main bearings to see if they are still standard or oversize, on many old engines, the crank has been turned and bearings will be stamped if they are over sized.
cranking up the oil pressure by shimming the spring with washers or stretching it will not make up for worn main, rod or cam bearings.
 

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