WVBill
Veteran Member
I have an old Kubota B6100DT. The FEL has a completely separate hydraulic system. As the weather started getting colder, I started noticing noise from the hydraulic pump whenever I actuated one of the hydraulic controls. The higher the engine RPM the louder the noise.
I concluded that this is pump cavitation noise due to thick oil. The oil in the reservoir was very thick (almost like honey) and a light brown color (like latte'). My father in law had used Ford Hydraulic oil in it for many years.
The manual for the loader finally came in last week so I set about changing the oil. The manual says to use 10W30 motor oil. 6.5 qt capacity. I described the situation to the service manager at my Kubota dealer and he said that there was probably also water in the system. He recommended that I drain the system and then flush it with a 50/50 mix of motor oil and diesel fuel before adding the new 10W30.
I drained the system, cleaned the strainer screen and put in 3 qts of the 50/50 mix. It wouldn't hold any more. I'm assuming that even with all the hydraulic cylinders completely retracted, there's still 3.5 qts of oil in the system (i.e. the reservoir only holds 3 qts of the total system capacity of 6.5 qts).
I cycled the system quite a few times with the 50/50 mix. The cavitation noise from the pump was gone.
I drained the 50/50 mix (much thinner now but still a light brown color and clearly contains small air bubbles), cleaned the screen and put in 3 qts of 10W30. Cycled that, drained it, cleaned the screen and re-filled with 3 qts of 10W30. With the 10W30 alone, the cavitation noise returned and I still see small air bubbles in the oil.
Apparently, 10W30 oil is still too thick. So based on the recommendations in other threads, I'd like to switch to synthetic oil.
That said, it seems that in each drain/re-fill, I can only replace half of the system's oil. I didn't mind the multiple drain/re-fills to flush the system when is was relatively inexpensive dino oil but I would like to minimize this when I put in synthetic. Also, everyone says not to mix dino and synthetic.
Any ideas on how to most efficiently get all of the old oil out of the system in order to replace it with synthetic? Should I disconnect all of the hydraulic lines from the cylinders and manually drain them?
WVBill
I concluded that this is pump cavitation noise due to thick oil. The oil in the reservoir was very thick (almost like honey) and a light brown color (like latte'). My father in law had used Ford Hydraulic oil in it for many years.
The manual for the loader finally came in last week so I set about changing the oil. The manual says to use 10W30 motor oil. 6.5 qt capacity. I described the situation to the service manager at my Kubota dealer and he said that there was probably also water in the system. He recommended that I drain the system and then flush it with a 50/50 mix of motor oil and diesel fuel before adding the new 10W30.
I drained the system, cleaned the strainer screen and put in 3 qts of the 50/50 mix. It wouldn't hold any more. I'm assuming that even with all the hydraulic cylinders completely retracted, there's still 3.5 qts of oil in the system (i.e. the reservoir only holds 3 qts of the total system capacity of 6.5 qts).
I cycled the system quite a few times with the 50/50 mix. The cavitation noise from the pump was gone.
I drained the 50/50 mix (much thinner now but still a light brown color and clearly contains small air bubbles), cleaned the screen and put in 3 qts of 10W30. Cycled that, drained it, cleaned the screen and re-filled with 3 qts of 10W30. With the 10W30 alone, the cavitation noise returned and I still see small air bubbles in the oil.
Apparently, 10W30 oil is still too thick. So based on the recommendations in other threads, I'd like to switch to synthetic oil.
That said, it seems that in each drain/re-fill, I can only replace half of the system's oil. I didn't mind the multiple drain/re-fills to flush the system when is was relatively inexpensive dino oil but I would like to minimize this when I put in synthetic. Also, everyone says not to mix dino and synthetic.
Any ideas on how to most efficiently get all of the old oil out of the system in order to replace it with synthetic? Should I disconnect all of the hydraulic lines from the cylinders and manually drain them?
WVBill
