135 massy Ferguson hydraulic problem

I have a 1967 massy Ferguson 135. Im having a hydraulic problem. Everything lifts and works properly with no weight and like for say a box blade. Everything works like it should. As soon as I put a lot of weight on like say a brush hog. The hydraulics will pick up and not stop untill it gets all the way raised up and it will lock. While its raising u have no control over it. Once it gets all the way up the pump continues to pump. I cant figure this out. I even bought another hydraulic top cover and put on it but it does the exact thing.. please help

Hello, looks like you have a breakdown in communication between
the position of the 3-point linkage, the quadrant lever and the pump
control valve. Forgetting about your second cover for the moment;
First of all check that the control valve lever works freely against the
spring through it’s full working range. Next, make sure that the pump
lever is correctly attached to the pump backplate by the popper
button. With the engine ‘off’, observe what is happening. With the
quadrant lever fully down, the pump lever should be leaning forward
in the discharge position. Raise the quadrant lever to about halfway.
The pump lever should move fully rear wards. Have an assistant lift
the 3-point linkage slowly. As the linkage nears the selected position
the pump lever should move to the near vertical neutral position.
Raising the quadrant further will repeat the process. When you lower
the W lever the cv lever will go forward into discharge. As your
assistant lowers the 3-point the cv lever will return to the neutral
position when it reaches the selected height. It would appear that the
cam on the ram arm on the main hydraulic shaft is not telling the
pump that it should be in neutral when the point of maximum lift is
reached. There are several things that can cause or contribute to
this. With the Draft lever lowered check for in/out movement at the
top link attachment point. There should be no end float present. The
assembly should be removed and the control spring checked to
ensure that it is tight to turn by hand. There may be damage or wear
in the position control spring frame within the cover which is
preventing the vertical lever moving the pump into the neutral
position when told to do so. Observe with the engine running this
time. If the pump lever remains leaning rearwards at full lift then that
is the area of the problem. It may be possible if you have enough
thread to unscrew the knurled screw on the vertical lever just enough
to move the pump into the neutral position at the selected Qw
position. If this does not work I think the next step would be to
remove the cover and carry out a full adjustment sequence but for
that you will need the special setting tools.
Let us know what you find.
DavidP,South Wales

Should be Q lever not W lever.
DavidP