Oil level inconsistant

[captmikem]

The hyd oil level on my MX 4800 never seems to stay the same, it shows nothing, quarter or half, and over full. Never consistent, and it does not matter if the loader is up, down, or half way.

I worry about it being over filled, but when it does not show on the sight glass for a few hours I worry about it being low… so I add a quart or half a gallon, pretty soon it is showing half or over.



Any ideas? Thoughts? Suggestions?

 

[Hugo Habicht]

Is the tractor perfectly level when you check the oil?

And I would think the level changes with oil temperature too.

 

[captmikem]

Is the tractor perfectly level when you check the oil?

And I would think the level changes with oil temperature too.

Yes, level. and it can be winter or summer, I would expect a slight change as the oil gets hot, but this is pretty radical.

 

[JonM]

hydrolix oil expanss a lot with heat

 

[NorthwoodsLife]

At refill measure the capacity that you put in per the specs, and don't sweat it.

Unless you have fluid leakage under the tractor...
Don't fix what isn't broken.

 

[captmikem]

At refill measure the capacity that you put in per the specs, and don't sweat it.

Unless you have fluid leakage under the tractor...
Don't fix what isn't broken.

That is my thought, there is never (well, occasionaaly a hose or fitting leak but usually just a drip that I fix quickly. But never any oil spots under the tractor when sitting and no oil trails when moving. Just hate to be under or over filled.

 

[InTheWoods]

Wouldn't the fluid level in the reservoir depend on the position of any hydraulic implements that are hooked up, including the 3PH?

 

[captmikem]

Wouldn't the fluid level in the reservoir depend on the position of any hydraulic implements that are hooked up, including the 3PH?

no, level stays the same with the 3p up or down, loader up or down, bucket rotated in or out.

 

[RCW]

no, level stays the same with the 3p up or down, loader up or down, bucket rotated in or out.

Just guessing, but possibly due to the geometry of the vessel/sump the fluid is in, I can see small variations in temp, etc. could/would change what you see in the sight glass.

As an example, my little BX takes about 3 gallons. The difference between off the dipstick and full is only about a quart + - - maybe 1.5 quarts.

The dipstick is in a narrow part of the sump. Little bit of fluid changes the level on the stick quite a lot.

Those sight glasses are often a problem for many owners.

I prefer a dipstick....

 

[Hugo Habicht]

Wouldn't the fluid level in the reservoir depend on the position of any hydraulic implements that are hooked up, including the 3PH?

Oil level does change with cylinder in or out. The rod displaces oil when in. But it may be too small to see.

In this case it is oil temperature. Thermal expansion of oil is way more than of the enclosure.

And position of the tractor has a huge impact. But you said it is perfectly level when you check it.

 

[Blondie70]

I don't think it can be hurt by overfilling....in fact, think it could be running out the top and still not hurt anything....it's low you don't want !!!!!!!

 

[McMXi]

hydrolix oil expanss a lot with heat

There's an equation for the expansion of hydraulic oil as a function of the coefficient of thermal expansion and the temperature change.

Reservoir Volume = System Volume * (1 + (β * ΔT)) where β is the coefficient of thermal expansion, and ΔT is the change in temperature.

Who knows what β is for UDT or UDT2, but if it's .0007 which is a common value for engine oil, and ΔT is around 100°F, then the volume of the hydraulic oil could increase by 7%. The MX6000 (similar to MX4800) supposedly has 11.6 gallons (46.4 qt) of hydraulic oil so with 7% expansion that would be 49.6 qt or an increase of about 3.25 qt.

Kubota says nothing in the owner's manual about oil temperature when checking hydraulic oil, only to lower the implement to the ground (for safety I assume), to park the tractor on level ground, and to shut off the engine. So now I wonder if the difference for an MX as indicated by A below is around 3 Qts. That would make sense to me.

 

[captmikem]

There's an equation for the expansion of hydraulic oil as a function of the coefficient of thermal expansion and the temperature change.

Reservoir Volume = System Volume * (1 + (β * ΔT)) where β is the coefficient of thermal expansion, and ΔT is the change in temperature.

Who knows what β is for UDT or UDT2, but if it's .0007 which is a common value for engine oil, and ΔT is around 100°F, then the volume of the hydraulic oil could increase by 7%. The MX6000 (similar to MX4800) supposedly has 11.6 gallons (46.4 qt) of hydraulic oil so with 7% expansion that would be 49.6 qt or an increase of about 3.25 qt.

Kubota says nothing in the owner's manual about oil temperature when checking hydraulic oil, only to lower the implement to the ground (for safety I assume), to park the tractor on level ground, and to shut off the engine. So now I wonder if the difference for an MX as indicated by A below is around 3 Qts. That would make sense to me.

View attachment 153428

I think you are correct, around 3 qtss. Pretty much the same for the MX. It does state not to start the engine if the oil is below the indicator, but I have that happen often. System holds 11.6 US gal. so it is a LOT of hyd fluid.