Is high engine oil pressure a bad thing?

[sarabande]

glad the problem is now solved, but I was really looking forward to the debate from m'learned friends running on for a bit. We were already halfway through to getting a communal degree in Tribology and Marine Engines.


Forum Power wins again.

 

[ianc1200]

Just in case this is of interest, I had a similar problem. The engine was a 5 cylinder 62hp 2.8L Nanni/Kubota. After just less than three years old the oil pressure gauge was beyond the highest reading (90 bar or PSI, can't remember). The agent was called, the gauge was replaced, no change, the high pressure relief valve was changed (this all taking 2 weeks whilst parts were ordered, and trip from the upper Thames to the Blackwater became in doubt), and the agent used a mechanical gauge and found the pressure to be 130. The expected pressure was 50-65. It was agreed the engine was to be lifted & examined under warranty, but I was determined to get to the Blackwater as only one crew left. I noticed this all seemed to be happening with the temperature at about 60C. I closed the seacock, got the temperature up, and the pressure dropped.......

However, two years later the engine had a monumental failure & I wished I had of had it looked at, could have saved a lot of grief.

The replacement engine also has high oil pressure until it's run at least 30 mins and up to temperature.

IanC

 

[jason -and the arguenauts]

1 bar is 1 atmosphere or about 15 psi so 90 bar would be 1350 psi. I dont think your engine would have reached that oil pressure.

Stu - I would think that gear oil is thicker too, but apparently not. See http://en.wikipedia.org/wiki/Gear_oil

 

[Heckler]

glad the problem is now solved, but I was really looking forward to the debate from m'learned friends running on for a bit. We were already halfway through to getting a communal degree in Tribology and Marine Engines.


Forum Power wins again.

Good innit?
Tribology, hmm, I think it was more about whether a pressure relief valve was working or not. Suppose the rubbing together of the plunger and the casting in the relief valve would qualify?
Seriously, there is some good stuff here BUT a lot of WAG goes on too! Plus a bit of strutting! I suppose that is what makes it in to a community, the other thing that is strange is ones perceptions of peeps, I know Richard M44 was expecting someone totally different to my true personna, plus savage seadog, sorry searush, looks just like his pic!
Stu

 

[alan_d]

Tribology is a facinating subject and frequently difficult for the lay person to understand.

"Tribology is the science and technology of interacting surfaces in relative motion." (Wikipedia)

And here was me thinking it was a sexual perversion ....

 

[Heckler]

1 bar is 1 atmosphere or about 15 psi so 90 bar would be 1350 psi. I dont think your engine would have reached that oil pressure.

Stu - I would think that gear oil is thicker too, but apparently not. See http://en.wikipedia.org/wiki/Gear_oil

Ermm, Quote from your site, "Gear oil is a motor oil made specifically for transmissions, transfer cases, and differentials in automobiles, trucks, and other machinery. It is of a higher viscosity to better protect the gears and usually is associated with a strong sulfur smell. The high viscosity ensures transfer of lubricant throughout the gear train. This is necessary since the devices needing this heavy oil do not have pumps for transferring the oil with only a portion of the lowermost gears bathed in an oil sump. This heavy oil can create viscous drag leading to inefficiencies in vehicle operation."
When I said SAE 90, gear oil is what I was referring to, perhaps my terminolgy is at fault and instead of saying SAE90 I should have said gear oil.
But any way, enough of this point scoring, this thread is going the way of others that i complain of where peeps wriggle and twist like a hsband and wife determined to have the last word in an argument!
Stu

 

[TQA]

Tribology, centistokes, pascals we are a right bunch of anoracks 46 posts so far and counting. Most on opening page.

Note to self "Gotta get a life"

 

[VicS]

When I said SAE 90, gear oil is what I was referring to, perhaps my terminolgy is at fault and instead of saying SAE90 I should have said gear oil.

You actually said "hypoid" but that's beside the point .
You are right that sae 90 gear oil would be more viscous that a 10/40 multigrade engine oil when cold.

However.

The viscosity specification of a sae 90 gear oil covers the same range of viscosity as as the specification for sae 40 and 50 single grade engine oils.

That perhaps is what confused Jason.

Bl*st. Ive agreed with you again.

 

[Heckler]

You actually said "hypoid" but that's beside the point .
You are right that sae 90 gear oil would be more viscous that a 10/40 multigrade engine oil when cold.

However.

The viscosity specification of a sae 90 gear oil covers the same range of viscosity as as the specification for sae 40 and 50 single grade engine oils.

That perhaps is what confused Jason.

Bl*st. Ive agreed with you again.

Wow getting better, I like fixing engines, Ive done enough of them, I like solving problems in fact I get just as much of a kick out of it as sailing! Sad innit?
Stu

 

[Heckler]

You actually said "hypoid" but that's beside the point .
You are right that sae 90 gear oil would be more viscous that a 10/40 multigrade engine oil when cold.

However.

The viscosity specification of a sae 90 gear oil covers the same range of viscosity as as the specification for sae 40 and 50 single grade engine oils.

That perhaps is what confused Jason.

Bl*st. Ive agreed with you again.

I was puzzled but looked back, in the first post i said sae90 and then later on hypoid
Stu

 

[VicS]

in the first post i said sae90 and then later on hypoid

Cant cater for all these inconsistencies

Lets start a new debate. (should put this thread to sleep with luck)

An grade 90 oil is not necessarily a hypoid oil. Hypoid oils are EP90

 

[tinkicker0]

Errr Vic....Nah i'll keep me gob shut.

 

[cliffordpope]

Anyway the important thing is that the excess oil has been drained off.
The main danger from overfilling is frothing, caused by the big ends striking the oil surface and whipping it into a lather, which has inadequate lubrication properties.

 

[TQA]

Cant cater for all these inconsistencies

Lets start a new debate. (should put this thread to sleep with luck)

An grade 90 oil is not necessarily a hypoid oil. Hypoid oils are EP90

A hypoid is a type of spiral bevel gear whose axis does not intersect with the axis of the meshing gear. The shape of a hypoid gear is a revolved hyperboloid (i.e., the pitch surface of the hypoid gear is a hyperbolic surface), whereas the shape of a spiral bevel gear is normally conical. The hypoid gear places the pinion off-axis to the crown wheel (ring gear) which allows the pinion to be larger in diameter and have more contact area. In hypoid gear design, the pinion and gear are practically always of opposite hand, and the spiral angle of the pinion is usually larger than that of the gear. The hypoid pinion is then larger in diameter than an equivalent bevel pinion.

A hypoid gear incorporates some sliding and can be considered halfway between a straight-cut gear and a worm gear. Special gear oils are required for hypoid gears because the sliding action requires effective lubrication under extreme pressure between the teeth.
[Wikipedia]

Extreme Pressure and a wiping action as the gears can not roll without moving require a special additive as you say. A typical hypoid oil is a SAE 90 base oil with an additive cocktail to resist the pressure and the wiping action inherent in the gear tooth profile.

Castrol call their hypoid oil Hypoy.

I knew an ex Rolls Royce mechanic who insisted on using it in his oil can when rebuilding engines saying it would maintain an oil film during those first seconds before the oil pump picked up and the system pressurised.

Anorack moment of the day. Now where is my life!

 

[Lakesailor]

I still have a little bottle of cam assembly oil that Kent Cams used to supply with new cams. It has some additives in it to make it very, very sticky for that same reason.
This Gear oil vs Engine oil viscosity discussion is going on all the time on US chainsaw sites. Chainsaw oil is also very sticky.