Large swing in oil pressure- How come?

[CO_Farmer]

Here's one I don't completely understand...The oil pressure on my YM2500 runs about 50 to 60 PSI at 2,000 RPM when it's first started, then it drops down to around 25 PSI after fully warmed up when the coolant is running around 180 degrees. I use either Delvac or Rotella 15W-40 oil, the same stuff as in my other diesels.

This seems like an awfully large drop in oil pressure, what could be causing it- Or could this be considered normal on a Yanmar?

 

[CO_Farmer]

Here's one I don't completely understand...The oil pressure on my YM2500 runs about 50 to 60 PSI at 2,000 RPM when it's first started, then it drops down to around 25 PSI after fully warmed up when the coolant is running around 180 degrees. I use either Delvac or Rotella 15W-40 oil, the same stuff as in my other diesels.

This seems like an awfully large drop in oil pressure, what could be causing it- Or could this be considered normal on a Yanmar?

 

[Soundguy]

It's just a bit loose.

My old gas antique tractors will start with 40 psi cold, and that becomes 10 psi hot... mains and cams... no biggie.. 25 psi is ok presure. What should alarm you is if you have a large oil pressure swing right after an oil change, or when working... that can mean a bad filter, bad oil, or a spun bearing. If it is a gradual drop in oil pressure over years of use.. it's normal wear and tear. If this happend all of a subben, I'd change the oil, and let it drain thru a white tshirt and look for sparklies, and then change the oil filter.. use a different brand from a different store... might even swap the gauge with a 9$ sunpro just for the heck of it. Grab a differnt batch of 15-40 oil.. since this is a test.. cheap is fine.. tsc 88 cent a quart or napa oil.. etc.. that way you can rule out bad products.. etc. I've seen lots of low oil pressure after a oil and filter change... usually all attributed to bad oil filter..

Soundguy

 

[Soundguy]

It's just a bit loose.

My old gas antique tractors will start with 40 psi cold, and that becomes 10 psi hot... mains and cams... no biggie.. 25 psi is ok presure. What should alarm you is if you have a large oil pressure swing right after an oil change, or when working... that can mean a bad filter, bad oil, or a spun bearing. If it is a gradual drop in oil pressure over years of use.. it's normal wear and tear. If this happend all of a subben, I'd change the oil, and let it drain thru a white tshirt and look for sparklies, and then change the oil filter.. use a different brand from a different store... might even swap the gauge with a 9$ sunpro just for the heck of it. Grab a differnt batch of 15-40 oil.. since this is a test.. cheap is fine.. tsc 88 cent a quart or napa oil.. etc.. that way you can rule out bad products.. etc. I've seen lots of low oil pressure after a oil and filter change... usually all attributed to bad oil filter..

Soundguy

 

[CO_Farmer]

Thanks for the thoughts, I've also been thinking that it's just a lot of hours on the beast. It's just about the same pressure regardless of oil filters. Does get better with a bottle of STP dumped in. Engine runs just fine, otherwise.
My service manual says to use straight 50 weight oil in the summer. Maybe I'll try that and see what happens.

What do you think a minimum safe hot oil pressure would be? 10 PSI at 2,000 RPM would make me nervous.

That's when I'm going to have to suck it up, pull the hamster wheel and rebuild it. Don't want to do it if I don't have to, but I also don't want to do a rebuild after running it completely into the ground and a rod puts a window in the crankcase...That gets more expensive, as you know ;-)

 

[CO_Farmer]

Thanks for the thoughts, I've also been thinking that it's just a lot of hours on the beast. It's just about the same pressure regardless of oil filters. Does get better with a bottle of STP dumped in. Engine runs just fine, otherwise.
My service manual says to use straight 50 weight oil in the summer. Maybe I'll try that and see what happens.

What do you think a minimum safe hot oil pressure would be? 10 PSI at 2,000 RPM would make me nervous.

That's when I'm going to have to suck it up, pull the hamster wheel and rebuild it. Don't want to do it if I don't have to, but I also don't want to do a rebuild after running it completely into the ground and a rod puts a window in the crankcase...That gets more expensive, as you know ;-)

 

[HGM]

Not having oil pressure experience with this engine, I would still not be alarmed by 25psi @2000RPM... Its only lube pressure, and to me thats pretty good..... Never checked mine, but I wouldnt give it a thought at that pressure.. Remember viscocity changes with temp..

 

[HGM]

Not having oil pressure experience with this engine, I would still not be alarmed by 25psi @2000RPM... Its only lube pressure, and to me thats pretty good..... Never checked mine, but I wouldnt give it a thought at that pressure.. Remember viscocity changes with temp..

 

[Jagmandave]

Is it easy to drop the pan? If so, a new set of rod bearings might improve things dramatically.............otherwise, I'd just go with heavier oil as you manual indicates. Sounds like normal wear to me too...........

 

[Jagmandave]

Is it easy to drop the pan? If so, a new set of rod bearings might improve things dramatically.............otherwise, I'd just go with heavier oil as you manual indicates. Sounds like normal wear to me too...........