Is high engine oil pressure a bad thing?

[zaragozo]

I have a Yanmar 4JHE-TBE in my boat which ran with perfect oil pressure (1-1,5 kp/cm2) before being serviced by a 'professional' marine engineering company. I provided the exact amount of new oil but they said they didn't need to use it all. I suggested that they didn't get all of the old out. They said they got out as much as the could. In the event I now get up to 4.5 kp/cm2 - well over the normal reading. They said it might be the oil pressure sensor that's gone wrong. The dipstick showed that the oil reservoir had been well overfilled and now after about another 150 nm of use it's still above the max level by a couple of cm.
I'm thinking maybe I should siphon off the excess? Would this lower the pressure? I've not had any other problems with this engine - it's a 2003 and has only done 650 hours. The operating temperature is normal, I can't see any leaks and am now getting a little paranoid as I am due on a longish trip shortly and wouldn't want the engine to split open or whatever.
I'd welcome any suggestions. The company which did the service had agreed to check the oil pressure with a gauge but haven't managed to get one yet - after 3 months...

 

[savageseadog]

Over filling the oil is highly dangerous to diesel engines, perhaps they know they can do this on your engine but it isn't normal. No it won't affect oil pressure, but it's possible they've either used the wrong oil or oil filter. Suggest you such out or drain the excess.

 

[earlybird]

I second that. Remove excess oil. Also, the high pressure suggests a possible restriction to oil flow, the bearings etc might suffer. You need to find the reason.

 

[Lakesailor]

Remove excess oil and try to get another pressure sender to check their theory. Doesn't have to be a new one, just one (borrowed perhaps) that you know works. If the excess pressure is causing oil starvation at the bearings or there is a jammed pressure relief valve that is creating higher pressure all the way through the system it can still cause damage. Too much pressure can be harmful as well as too little.
You need to get it sorted before you run it any more.

 

[fergie_mac66]

I was always told that too much pressure/oil will blow oil seals

 

[tinkicker0]

High oil pressure puts strain on gaskets and seals within the engine. It can also cause filter canisters to deform or even split open in extreme cases.

Without knowing the lube system layout on your engine it is difficult to diagnose, but as the others have mentioned, suspect the sender unit first.
Most oil filters have a bypass valve that opens if they are clogged, so I doubt your crank is getting starved, however your oil may not be getting filtered.

Most high oil pressure woes are usually caused by a stuck oil pressure relief plunger, this may be mounted on your oil pump, or in your engine block. It may be accessible without stripping the motor or it may not.

High oil pressure would not normally be caused by overfilling the sump. Low pressure maybe if it is high enough. However as others have said, it may place severe strain on your oil control rings and result in a smoky motor.

I do not know your particular motor, so I am only speaking in generallities.

 

[lw395]

Without knowing the lube system layout on your engine it is difficult to diagnose, but as the others have mentioned, suspect the sender unit first.
Most oil filters have a bypass valve that opens if they are clogged, so I doubt your crank is getting starved, however your oil may not be getting filtered.

Most high oil pressure woes are usually caused by a stuck oil pressure relief plunger, this may be mounted on your oil pump, or in your engine block. It may be accessible without stripping the motor or it may not.

I would add to this that I've had an engine quickly go from oil pressure relief stuck closed to stuck open, I think the pressure got high enough to overcome the friction and open the relief at moderate revs, then drastic loss of pressure as the revs dropped.

I would suggest getting another gauge and sender or a mechanical gauge to check the old one. Maybe mount it in place of the oil light switch. Adaptors are available from motorsport places. Merlin at Castle Combe helped me.
Good Luck!

 

[Heckler]

I have a Yanmar 4JHE-TBE in my boat which ran with perfect oil pressure (1-1,5 kp/cm2) before being serviced by a 'professional' marine engineering company. I provided the exact amount of new oil but they said they didn't need to use it all. I suggested that they didn't get all of the old out. They said they got out as much as the could. In the event I now get up to 4.5 kp/cm2 - well over the normal reading. They said it might be the oil pressure sensor that's gone wrong. The dipstick showed that the oil reservoir had been well overfilled and now after about another 150 nm of use it's still above the max level by a couple of cm.
I'm thinking maybe I should siphon off the excess? Would this lower the pressure? I've not had any other problems with this engine - it's a 2003 and has only done 650 hours. The operating temperature is normal, I can't see any leaks and am now getting a little paranoid as I am due on a longish trip shortly and wouldn't want the engine to split open or whatever.
I'd welcome any suggestions. The company which did the service had agreed to check the oil pressure with a gauge but haven't managed to get one yet - after 3 months...

Its a times like this when peeps make "educatd guesses" that I despair. FACT: the oil pressure in all the engines that I have worked on for nigh on 50 years does not pressurise oils seals or piston rings!
Generically speaking, there is an oil pump, with a suction pipe that is positioned in the sump, it picks up oil, pumps it thru an oil filter and then in to galleries in the engine block, usually there is a pressure relief valve in the gallery that controls the oil pressure. The galleries feed the oil, thru internal drillings to the main bearing housings where it lubricates the main bearing journals and enters the crank shaft where galleries carry it to each big end bearing, usually there is a fine drilling in each con rod which allows oil from the big end to spray the under side of the pistons and to lubricate, thru holes in the piston lands, the piston rings. Further galleries in the block carry oil up to the rockers or cam shafts which allows lube to reach the top end of the engine and drain back down to the sump. No where is there any pressurised oil seals as such. The oil seals at the front and rear of the engine act as a barrier rather than a pressurised cavity. The running clearances of the bearings dont allow pressurisation of the bearing "housings" The overall pressure is governed solely by the oil pressure relief valve. The capacity of the pump is such that when the bearings get worn then the loose fit governs the oil pressure. That is basically how the vast majority of engines work.
Going to the OP problem. There is every possibility that the oil pressure relief valve is stuck, OR depending where the oil filter is in the circuit, that it is the wrong one or it is blocked. I had it happen to me on a Ford V 6 years ago, it used to explode the oil filters!.
I would say that if a "professional" has overfilled the engine by a couple of cms then he is not very professional at all and I would be questioning what else he has done wrong.
Wrong oil filter, quite easily checked and remedied, too much oil, again quite easily remedied BUT is it the right oil? if he has put sae 90 oil in by mistake? that would give excessive pressure by not allowing the pressure relief valve to dump the exessive pressure quick enough. I think one could say that if the guage worked before, what has changed? oil and filter, therefore its a good chance that the guage is reading correctly.
I would change the oil and filter quickly, running as is, is risking damage to the engine.
Stu

 

[tinkicker0]

Its a times like this when peeps make "educatd guesses" that I despair. FACT: the oil pressure in all the engines that I have worked on for nigh on 50 years does not pressurise oils seals or piston rings!


You don't call O ring seals, sealing oil galleries seals then?

As for the piston rings, if you read my post, I state that it is overfilling the oil to the extent of the crank webs flinging it up the cylinder bores at a couple of pints a second that overload the oil control rings, they float away from the cylinder wall on the oil ramp, becasuse the drillings cannot clear the oil fast enough, allowing oil into the top of the cylinder. This then burns and makes smoke. Unfortunately by the time the overfill condition has gone, the bores are glazed and high oil consumption continues.

Nothing to do with oil pressure.

 

[Heckler]

Its a times like this when peeps make "educatd guesses" that I despair. FACT: the oil pressure in all the engines that I have worked on for nigh on 50 years does not pressurise oils seals or piston rings!


You don't call O ring seals, sealing oil galleries seals then?

As for the piston rings, if you read my post, I state that it is overfilling the oil to the extent of the crank webs flinging it up the cylinder bores at a couple of pints a second that overload the oil control rings, they float away from the cylinder wall on the oil ramp, becasuse the drillings cannot clear the oil fast enough, allowing oil into the top of the cylinder. This then burns and makes smoke. Unfortunately by the time the overfill condition has gone, the bores are glazed and high oil consumption continues.

Nothing to do with oil pressure.

Stop digging dear boy!
Stu

 

[VicS]

I would change the oil and filter quickly, running as is, is risking damage to the engine.

Sensible advice there i think from Stu. Oh the pain of having to agree with him.

Its no guarantee that it will cure things esp if the pressure relief valve has stuck but a sensible thing to start with.

Not sure by any means but I think the relief valve on these engines is part of the oil pump assembly. I found a workshop manual but not for exactly the same engine.

Find a different mechanic next time!

 

[tinkicker0]

Stop digging dear boy!
Stu

Thank you for your entertaining article on how oil distribution pathways exist within an engine. I am suitably impressed with your knowledge.

High oil pressure would not normally be caused by overfilling the sump. Low pressure maybe if it is high enough. However as others have said, it may place severe strain on your oil control rings and result in a smoky motor.

however re reading the above. I can see where I was not clear in the fact that overfilling would cause ring problems, not pressure. My bad syntax.

 

[Heckler]

Thank you for your entertaining article on how oil distribution pathways exist within an engine. I am suitably impressed with your knowledge.

High oil pressure would not normally be caused by overfilling the sump. Low pressure maybe if it is high enough. However as others have said, it may place severe strain on your oil control rings and result in a smoky motor.

however re reading the above. I can see where I was not clear in the fact that overfilling would cause ring problems, not pressure. My bad syntax.

Still digging!
Stu

 

[Heckler]

Sensible advice there i think from Stu. Oh the pain of having to agree with him.

Its no guarantee that it will cure things esp if the pressure relief valve has stuck but a sensible thing to start with.

Not sure by any means but I think the relief valve on these engines is part of the oil pump assembly. I found a workshop manual but not for exactly the same engine.

Find a different mechanic next time!

Hee hee
Stu

 

[TQA]

This is something that you should get checked before running the engine further. If you have a stuck pressure relief valve the oil pump has to work much harder and the drive to it can fail.

N.B. A failed oil pressure sensor is the more likely cause of the high reading but it is a potentially serious problem.

Overfilling the sump does not usually cause any problems unless the level is high enough to allow the crankshaft to dip into it. If this happens the oil may froth which worsens the problem and oil gets splashed onto the cylinder walls , this often leads to oil in the combustion chamber and LOTS of blue smoke.

An old fart now retired with Diploma from the Institute of the Motor Industry and a City and Guilds Full Technology Certificate plus a few years "On the tools"

 

[Heckler]

I have a Yanmar 4JHE-TBE in my boat which ran with perfect oil pressure (1-1,5 kp/cm2) before being serviced by a 'professional' marine engineering company. I provided the exact amount of new oil but they said they didn't need to use it all. I suggested that they didn't get all of the old out. They said they got out as much as the could. In the event I now get up to 4.5 kp/cm2 - well over the normal reading. They said it might be the oil pressure sensor that's gone wrong. The dipstick showed that the oil reservoir had been well overfilled and now after about another 150 nm of use it's still above the max level by a couple of cm.
I'm thinking maybe I should siphon off the excess? Would this lower the pressure? I've not had any other problems with this engine - it's a 2003 and has only done 650 hours. The operating temperature is normal, I can't see any leaks and am now getting a little paranoid as I am due on a longish trip shortly and wouldn't want the engine to split open or whatever.
I'd welcome any suggestions. The company which did the service had agreed to check the oil pressure with a gauge but haven't managed to get one yet - after 3 months...

Ahem, now the boys have stopped scrapping/strutting, cheapest and easiest way to answer the question, change the oil and filter and see what transpires.
Stu

 

[savageseadog]

Further to what I've already said, there are possible liability issues here. If said pro mechanic has buggered your engine then he could be legally liable. If you do anything yourself, especially without consulting him or inviting him to put the problem right you won't have any chance of recovering your losses. I'm not sure exactly what to suggest but I would understand if you didn't want him near your engine again, but that is probably what you're going to have to do though. The other courses of action would be to get an independent engineer or surveyor.

As a first step I would inspect the oil filter and note its make and part number and find out if it's the right item. I would also take a sample of the oil preferably witnessed and retained independantly.

 

[Lakesailor]

Well. What a pissing contest this has turned into.

I think zaragozo can rest assured that all avenues have been explored.

If there is a concensus it's not to run the engine much until you have determined why the pressure is too high. Damage can occur.

 

[Heckler]

Well. What a pissing contest this has turned into.

I think zaragozo can rest assured that all avenues have been explored.

If there is a concensus it's not to run the engine much until you have determined why the pressure is too high. Damage can occur.

Hee hee!
Stu

 

[Lakesailor]

No-one has remarked on the OP's comment

and now after about another 150 nm of use it's still above the max level by a couple of cm

which would suggest the motor is either very robust, or it is just the sender that's at fault.