Dave M7040
Elite Member
- Joined
- Dec 10, 2012
- Messages
- 2,757
- Location
- Williamstown Ontario Canada
- Tractor
- Kubota M7040 Nuffield 465
The following comments are a bit generic and may not apply to a specific model.
I would differ on the Kubota having a main relief valve and then a relief valve in the loader valve.
Look for a label on the Kubota down on the right side where the loader valve connects into the main system. Typically there is a caution label warning not to disconnect the power beyond bypass as the main pump will be destroyed.
If there is no loader, Kubota puts a hose loop to direct the main pump flow to the rear of the tractor where the only relief valve is which controls the 3 pt hitch and rear remote pressures.
When the loader valve is installed, the pb loop is broken, main pump discharge goes to loader valve IN and the loader valve PB connects where the loop previously was to continue to power the rear of the tractor. Now the loader relief valve is the first one in the circuit and limits the max pressure any downstream relief valve can achieve. If you try and adjust the relief pressure for the 3 pt and rear remotes you will soon learn that it will not go above the loader relief valve setting.
The 3rd function is now downstream of the loader valve and while I do not think the 3rd function has a relief valve, even if it did, the loader relief would limit the max pressure.
My caution to owners working on hydraulics is for them to recognize there is no "Lets try it and see what happens."
.
In milliseconds the main pump is destroyed and expensive components also.
Dave M7040
I would differ on the Kubota having a main relief valve and then a relief valve in the loader valve.
Look for a label on the Kubota down on the right side where the loader valve connects into the main system. Typically there is a caution label warning not to disconnect the power beyond bypass as the main pump will be destroyed.
If there is no loader, Kubota puts a hose loop to direct the main pump flow to the rear of the tractor where the only relief valve is which controls the 3 pt hitch and rear remote pressures.
When the loader valve is installed, the pb loop is broken, main pump discharge goes to loader valve IN and the loader valve PB connects where the loop previously was to continue to power the rear of the tractor. Now the loader relief valve is the first one in the circuit and limits the max pressure any downstream relief valve can achieve. If you try and adjust the relief pressure for the 3 pt and rear remotes you will soon learn that it will not go above the loader relief valve setting.
The 3rd function is now downstream of the loader valve and while I do not think the 3rd function has a relief valve, even if it did, the loader relief would limit the max pressure.
My caution to owners working on hydraulics is for them to recognize there is no "Lets try it and see what happens."
.
In milliseconds the main pump is destroyed and expensive components also.
Dave M7040
