MF 135 hydraulic position control. Help, I'm stuck.

My position control doesn't work (see my last post for the exciting story so far) and I'm still trying to work out why. The grass is still growing …

I've had 2 suggestions (thank you guys) on what might be the problem and I think I've checked them both out:

1) the spring on the "dog" linkage: it's definitely there and seems strong enough. The linkages seem straight (see photos). The control valve moves smoothly by hand.

2) the draft control spring: there doesn't seem to be any end float.

The lift works using the draft control (just not very well, as you'd expect). It seems to have plenty of power though there is probably a leak(s) as the lift will not stay up, but I think that's a separate problem from the position control.

Other things I've found which might (or might not) have a bearing: dashpot is broken as shown in the photo; the relief valve is the compact type so, from what I've read, I don't expect the response control to work. I found an old post from Big Dean referring to a part that tends to comes loose stopping the position control working, after the tractor has an impact, but I can't find out any more on this. Oh, and the mounting lug on the ram cylinder is broken (see photo).

Should I overhaul the draft control assembly (no lathe to remove the "gripping weld", DavidP. Just the angle grinder …) and the control valve, put it back together and see if there's an improvement? I'd be really grateful for any suggestions on the next step.

Hello,
Superb photos! If the lug of the lift cylinder is broken that can be enough to prevent the position control working. The cylinder will lift in one corner and probably 'blow' the O ring.
To check whether everything in the lift cover is working requires a bit of mental dexterity. First of all position the hydraulic cover upside down but in a position where the upper lift arms can be lifted by hand and lowered. Have an assistant to hand to move the upper lift arms.
Tell the assistant to hold the upper arms up..in effect in the lowered position when fitted. Move the Position Lever into the lowered position. The vertical lever should now be pushed forward (as in fitted position) to put the control valve in the 'discharge position.
To recap if the cover were fitted; the position control lever is down, the 3-pt is down and the vertical lever is leaning forward. Exert gentle pressure rearward on the vertical lever but not enough to move it.
Now raise the Position Control lever slowly. The vertical lever will move rearward (as if fitted) through the neutral position and into the pumping position. Leave the PC lever at about halfway. Tell you assistant to lower the upper lift arms slowly (raise them when fitted). As the upper arms approach the selected position of the PC lever the vertical lever should move into the neutral position. If it does this it is working OK. You will probably need to do this quite a few times to firstly understand how it works and the relationship between the PC lever, upper lift arms and vertical lever position.
If you are able to support the hyd cover right way up it will be a lot easier.
DavidP

I could not agree more about the photos, they are indeed superb.
"Witzend", may I ask which make and model of camera you are using?

Never mind the tractor problem.....just post a photo of the camera!!!!!!!!
DavidP

Why didn"t I think of this before? "Canon EOS 350 Digital " unless Picasa is lying to me!

Bit better than a Box Brownie then!!!

David

No, it was one of these (with the optional flashcube, of course). Honest.

I had one of those ,Terrific, I don"t think we can even buy films (126?) for that here now