John Deere 3650 rear linkage wont lift

[Mark7810s]

Afternoon,
Have got a bit of a head scratcher with a 3650 where the rear linkage wont lift unless a spool valve or the steering is deadheaded. The system is achieving 1900psi tested at the spools. Im hoping its not a cab and top cover off job but got a feeling it might be.

Thanks in advance

 

[Tractortech]

Now Then..
For a start, you should have 190 bar (2750 Psi) at the spool couplers.
The steering priority valve will be set somewhere around what youte getting
As it's a true closed centre system, dead ending an SCV shouldn't make any difference.. I would disconnect the steering and cap it off, do the same with the rear spool block. You can also disconnect the pressure pipe from the pump underneath the clutch housing and put a gauge in there on the end of the pipe....

 

[Mark7810s]

My mistake ment to put 190bar. Thats a good shout remove the two other systems and see what changes. I should also at that stopping and restarting the tractor will also lift the linkage if the lift leaver is raised position while the tractor is started.

 

[Tractortech]

What history do you have with this thing?? Has it had an 'overhaul'/'restoration' or is it a worker??
Has this been developing for a while or has it suddenly happened??

 

[Mark7810s]

Not a-lot of history unfortunately problem developed a few years ago and has been sat on a hedge cutter till my friend recently purchased it.

 

[Tractortech]

As a guess, the lift valve will be sticking inside the rockshaft housing. Operating the steering will drop the pressure on it. At that point it will spring onto the operating rocker... 50 series had polished spools and different O-rings to the 40 series. They were less bother, but sticking is a possibility.
Csb off, rockshaft off, new genuine bobbins in. Do any other age related jobs, then you'll have some reliability..

 

[Mark7810s]

I was afraid we were at this stage with it! Would also explain removing the pressure turning off the tractor then turning it back on and it lifting.

 

[Tractortech]

I find there's nowt worth watching on the telly at the moment, so you might as well fix stuff all night.. 🛠