John Deere 300 Hydraulics stop when hot

[jcaldwell]

My JD 300 backhoe has stopped working when it gets warmed up. Hydraulics and transmission. When it cools off, everything works again. I've changed the filters, fluid, and cleaned the sump screen. Any idea whats causing it?
 

[Tx Jim]

Welcome to YT
Since trans stops operating I'm going to guess that the low pressure trans pump circuit has an internal leak or worn trans pump. A very large high pressure internal could cause same problem. JD closed center hyd system such as your 300 has require "good diagnostics" to determine the problem. Check hyd filter relief valve(keys18-20) to be sure it's not stuck open. Check trans pump output by removing hyd filter cover with drain pan underneath then operate engine for 15 seconds to check pump output.

I also suggest to check temp of each external hyd component with a hand held laser thermometer.

Remember diagnostics-diagnostics- diagnostics Good Luck.


 

[jcaldwell]

Will do. I know everything I touch in the hyd system gets very hot when I've used the hoe for awhile. The steering column will burn my leg if I touch it.
 

[Tx Jim]

Steering column o-rings have a long history of leaking causing hyd oil to heat & cause hyds to get sluggish. I suggest to acquire a JIC female cap then next time you need to operate backhoe disconnect steering supply line install female cap on main hyd line then see if hyd's operate cooler/better.
 

[jcaldwell]

just so I understand, this would cap off the power steering? See if I can operate without power steering and see if it corrects the heating issue?
 

[Tx Jim]

Yes capping power steering supply line then operating hyd's is a diagnostic step aka process of elimination.
 

[buickanddeere]

Also time to make certain that there is no oil returning to the tractor from the loader or backhoe . When no function is selected.