Oil Pressure Driving Me Crazy - Not Cam Plug

[JohnDB]

... is the dipstick tube original (not the sort that normally goes down through a hole in the block) or the right length for that dipstick?

Didn't get any bites on that question, so took a brief look at a D950 parts list which indicates that you don't have the standard dipstick arrangement. So the tube and dipstick is probably a special, maybe borrowed from a different series Kubota. The D950 (anyone, correct me if I'm wrong) has the dipstick hole nearer the front of the engine. Relocating it 1/2 way back makes some sense for a tilted engine. That oil level would have to come down a loooong way to expose the oil pickup (which according to the diagram I saw is towards the rear anyway) so that shouldn't be a problem. I reckon think about Wolfman's question about oil quantity, and depending on that, consider operating the engine with a lower oil level and keep an eye on the oil temperature as well oil pressure.

Don't know if the yellow line correctly shows the standard oil level (below the line of the counterweights), but operating for an extended period with a 7 deg. tilt might causes rear counterweights to whip up oil. And when your boat is cruising, does that change the angle further... bow up, stern down? Just my 2c.

[edited to add question about change in boat/engine angle when cruising]

 

[GreensvilleJay]

I have to wonder how hot the oil is, as normally 'oil pan' heat released into the air but in the belly of a boat, it can't escape nearly as fast ? I'd expect to have 1 or 2 powerful fans to blow a LOT of air at the oil pan ?? An oil cooler would help both to cool and possibly reduce foaming.

 

[lugbolt]

Since there are no bearings in the cam to block, I was not aware that checking them was a thing, so that is one thing I didn't do that could be a potential cause of my issue. But of course it's a lot of work chasing a potential wild goose. I did check all bearing clearances and with the new bearings they were within spec. The engine only has 1400 hours so it'd be surprising since I only saw one person online mention the cam to block being an issue, but the engine was mistreated by prior owner so it's hard to say. Included photo of the cam I had taken during rebuild in the original post, but can't make much just looking at it.

since there is an oil clearance, yes, it needs to be checked. The cam wears and the block wears. Even if it's a .001" combined amount of wear, it adds up. Most people never check it but I have and I've seen the cam worn a little bit which can cause exactly what you are describing.

 

[jlm46]

Didn't get any bites on that question, so took a brief look at a D950 parts list which indicates that you don't have the standard dipstick arrangement. So the tube and dipstick is probably a special, maybe borrowed from a different series Kubota. The D950 (anyone, correct me if I'm wrong) has the dipstick hole nearer the front of the engine. Relocating it 1/2 way back makes some sense for a tilted engine. That oil level would have to come down a loooong way to expose the oil pickup (which according to the diagram I saw is towards the rear anyway) so that shouldn't be a problem. I reckon think about Wolfman's question about oil quantity, and depending on that, consider operating the engine with a lower oil level and keep an eye on the oil temperature as well oil pressure.

View attachment 159118
Don't know if the yellow line correctly shows the standard oil level (below the line of the counterweights), but operating for an extended period with a 7 deg. tilt might causes rear counterweights to whip up oil. And when your boat is cruising, does that change the angle further... bow up, stern down? Just my 2c.

[edited to add question about change in boat/engine angle when cruising]

Thank you sir, yes the boat angle changes a lot with rocking and yes like you saw the dipstick tube is a marinized thing on this engine because the modified exhaust manifold blocks the standard dipstick location. I brought the oil level down to half way between full and empty...which really should still be ok anyway, to see if it makes a difference and will test in next few days. Like you said the oil pickup is way lower in the pan and the designer who marinized prob went very conservative.

I cant properly answer the questions about amount of oil used in the past except that its approx 4 quarts, i always went by the dipstick because engine angle and drain location on this modified pan prevents fully draining each time.

Will test soon and see if it was aeration the whole time and will report back

 

[jlm46]

since there is an oil clearance, yes, it needs to be checked. The cam wears and the block wears. Even if it's a .001" combined amount of wear, it adds up. Most people never check it but I have and I've seen the cam worn a little bit which can cause exactly what you are describing.

Yes i wish i had known to check it but good to know its one possible cause...if i have no luck with other paths i could always make it a winter project to take the cam out and measure it and the block. Thanks for the comment

 

[jlm46]

I have to wonder how hot the oil is, as normally 'oil pan' heat released into the air but in the belly of a boat, it can't escape nearly as fast ? I'd expect to have 1 or 2 powerful fans to blow a LOT of air at the oil pan ?? An oil cooler would help both to cool and possibly reduce foaming.

I wondered the same and used a temp gun at one point to measure the temp of the front cover at the bottom and oil pan and the highest i could find was low 200s hot which didnt seem unusual. I run a 160 thermostat on this engine while some others run a 180 thermostat so i think im running cooler than some others do. I havent had overheating issues or anything.

 

[JohnDB]

... yes the boat angle changes a lot with rocking ...

Not thinking so much of rocking, but the sustained angle at whatever speed it can spend a lot of time at.

 

[jlm46]

Not thinking so much of rocking, but the sustained angle at whatever speed it can spend a lot of time at.

Oh gotcha, nothing like that, its a sailboat and maximum speed is around 7-8mph with this engine, which doesnt change the angle by any significant amount. This engine was used on tons of these boats and has a very healthy online community but this topic only ever leads to oil sensor or cam plug issues unfortunately, nothing like all the ideas raised by the great comments in this thread by everyone.

 

[JohnDB]

Oh gotcha, nothing like that, its a sailboat and maximum speed is around 7-8mph with this engine, which doesnt change the angle by any significant amount. This engine was used on tons of these boats and has a very healthy online community but this topic only ever leads to oil sensor or cam plug issues unfortunately, nothing like all the ideas raised by the great comments in this thread by everyone.

Cool, thanks for explaining. Yes this forum is the motherlode of info on Kubotas.

 

[jlm46]

So I tested this today with the oil level half way down between "F" and "E' on the dipstick and I can't tell if its my imagination and poor scientific method here or if it actually did improve but it felt a little better.
Started off at 42psi cold as usual, and once hot I was at about 30psi at 2500rpm, 20psi at 1600rpm, 10psi at 1100rpm. If i went down to idle at 1000rpm I still got the buzzer, but if i waited only 1 minute instead of the usual 5-10, then I could go to idle and get 10psi.
Temperature-wise, at 2500rpm I was getting 190-195 degrees on the oil pan and around the bottom of the front gear cover where the pressure relief valve and oil filter are. When I waited a minute at 1100rpm and then lowered to idle at 1000rpm without getting the buzzer, the temp had dropped to 185-188. I wonder if only a few degrees is also making a difference like a tipping point.

Next step for next week is to try the straight 30 or 40 weight oil suggested by others in this thread and see if it makes a difference.

Thanks everyone!

 

[JohnDB]

So I tested this today with the oil level half way down between "F" and "E' on the dipstick and I can't tell if its my imagination and poor scientific method here or if it actually did improve but it felt a little better.
Started off at 42psi cold as usual, and once hot I was at about 30psi at 2500rpm, 20psi at 1600rpm, 10psi at 1100rpm. If i went down to idle at 1000rpm I still got the buzzer, but if i waited only 1 minute instead of the usual 5-10, then I could go to idle and get 10psi.
Temperature-wise, at 2500rpm I was getting 190-195 degrees on the oil pan and around the bottom of the front gear cover where the pressure relief valve and oil filter are. When I waited a minute at 1100rpm and then lowered to idle at 1000rpm without getting the buzzer, the temp had dropped to 185-188. I wonder if only a few degrees is also making a difference like a tipping point.
...

With a slight lowering of oil level you got a measurable improvement (subject to scientific method so before draining and refilling, why not try it on "E"? You aren't at all likely to run it out of oil due to the deep oil pickup. Temperature rise due to lower oil quantity **might** be a result... but you are already monitoring that, and anyway we already know that the dipstick markings are suspect and who knows how much oil is really in the sump anyway. It might be perfectly fine and your experiment will go a long way to informing that view.

Its a cheap and safe experiment before you start doing other things.

Also measure the oil quantity like Wolfman suggested. .

Not to say that it isn't any of the issues raised here, but you may as well conclude the oil level experiment first