Oliver 1855 diesel oil pressure problem

[Oliver1855]

I have a 1972 Oliver 1855 diesel that after initial startup, will idle around 55psi oil pressure and at 2000RPM its around 75psi. After using it for over an hour, oil press drops to 15-20psi @ idle and 35-40psi @ 2000RPM. Has anyone run across this before? Could it be oil pump? gauge? It runs great with almost no blowby or leaks. After its shut off and cools for 30 min or so, it will have good pressure again. Any help would be appreciated! Thanks

 

[Ranch_Hand_Supp]

I am not a OLIVER expert.........but what you described I would first screw in a Oil Pressure Gauge to determine if the problem is in the engine or in the oil pressure sending unit and or gauge.

I have found in the past on some engines that loose oil pressure after reaching operating temp or run for a little while.... that the oil pump pickup screen in the oil pan was getting restricted [sludge, metal, old gasket etc]. and when you would cut the engine off and let it set for awhile the trash would fall off the screen....re-start and have oil pressure again. I have also had bearings cause this and with no sounds of bearing going bad.

You could drain and filter the engine oil when this happens [hot engine] to see if you can find anything in the oil that does not look right. From trash to metal.

If I were to just jump in and do something ...I would drop oil pan and look for trash in the bottom of pan and inspect oil pump pick screen.

Just food for thought,
Ronald

 

[js5020]

I would definately double check the gauge for starters, can't recall for sure but I think there is a bypass valve in the filter housing, but you have a 55 that has a wak in it and not a perkins, might pay to get a shop manual, I don't think you can get at the oil pump without pulling the engine, I could be wrong it's been 15 or so years since I worked on one of these.

 

[Jagmandave]

Sounds pretty normal for a 33 year old engine.........how many hours are on it? Before I went to the trouble of dropping the pan, I'd consider going up in viscosity on your engine oil and see how it does.

 

[Oliver1855]

The gauge thats on it is a mechanical gauge. It has almost 4,000 actual hours and we use 15w40 Rotella oil. I will check the mentioned ideas (thanks!) and post back here when I find the problem. It has cooled down out here a little and the hot pressure has come up to 40 psi now, if that tells you anything.
Thanks again

 

[oliver28472]

For what its worth, I ran a 1650 with a 10' pull type bush hog through fescue Saturday. It was barking pretty good. I noticed the oil pressure went down to about 36 on it after warming up. The fescue had not been cut this year. Had to run in 3rd. This one has the 2-speed, not over-under like yours. There is another site you may want to post the same question. Try ytmag.com. They have an Oliver discussion forum there with some good retired Oliver mechanics. Have you had this tractor long? Do you know if it has had the updates done on the engine? Does it have the engine oil cooler on the side of the block?

 

[Jagmandave]

Sounds like you all are saying the same as me, low pressure due to high oil temp and some wear on the engine. A thicker base stock oil may help, ie 20W40 instead of 15 or maybe even a straight grade 30 or 40W. Then pull the pan this winter and check for worn bearings.

 

[jerry shannon]

I will be watching this closely on my 1855. I have just picked up a 1974 Oliver 1855. Had a complete rebuild on it several years ago. Runs strong, shifts smooth and sounds fantastic. I will start paying attention to the oil pressure gauge on mine for signs of drop off after warm. Its cold here in Michigan and have only had the machine for a few weeks so have not worked it hard yet. Glad to find some Oly owners out there.

 

[jerry shannon]

I will be watching this closely on my 1855. I have just picked up a 1974 Oliver 1855. Had a complete rebuild on it several years ago. Runs strong, shifts smooth and sounds fantastic. I will start paying attention to the oil pressure gauge on mine for signs of drop off after warm. Its cold here in Michigan and have only had the machine for a few weeks so have not worked it hard yet. Glad to find some Oly owners out there.

 

[Jerry/MT]

I have a 1972 Oliver 1855 diesel that after initial startup, will idle around 55psi oil pressure and at 2000RPM its around 75psi. After using it for over an hour, oil press drops to 15-20psi @ idle and 35-40psi @ 2000RPM. Has anyone run across this before? Could it be oil pump? gauge? It runs great with almost no blowby or leaks. After its shut off and cools for 30 min or so, it will have good pressure again. Any help would be appreciated! Thanks

The most likely causes for the loss in ol pressure that you describe are a stuck open relief valve, and /or a worn oil pump, and/or worn main and rod bearings.
As the oil heats up and the engine warms. the oil viscosity drops and the engine clearances assume their running values. These combine to cause a drop in oil pressure. In a new engine, the relief valve should mantain the oil pressure at a fixed value, the valve being more open when the oil is cold and less open when the engine is warm. A the engine wears , the releif valve will reduce its opening to zero andll only the bearing clearances control the oil pressure.This will result in a variation in measure oil pressure with oil temperature. As the engine wears further the oil pressure will drop as it warms up untill the clearance become so large that the oil pressure drops below the min allowable spec. Unfortunately , a worn oil pump will cause the same indications for oil pressure as worn bearings and so will a stuck open relief valve.

We have a Ferguson TO-30 with around 700 hrs on a remanufactured engine that maintains it's oil pressure at 27 psi (spec is 25-30 psi) from cold start up to operating temperature and from idle to max rpm. That indicates to me that the relief valve setting is maintaining the oil pressure and there is minimal wear in the pump and bearings.

To determine the cause of your reduction in oil pressure will require you to pull the pump and check the relief valvefor sticking open and the pump clearances. If they are within spec than it time to Plastigauge the main bearings and consider replacing the bearings.