Rock'n Tractor

[dingleberry]

Rock\'n Tractor

I have recently replaced the hydraulic FEL valve on my tractor. I also drained, replaced filter and all fluid in the hydraulic system. I just bought a box blade and put on the tractor. I have only owned the machine a short time, 6 mos, and have never used anything with the three point. I have only used it with the bhoe or nothing on the back.

WHen the tractor sits and idles and the box blade is up the box blade will start rocking up and down. The slower the idle the more it seems to rock. THe FEL will also rock up and down but I think this is a result from the box blade on the three-point rocking.

Any explanations? the tractor FEL or backhoe never did this before.

Thanks,
D

 

[SnowRidge]

Re: Rock\'n Tractor

I assume you mean that the BB sort of bounces? I have had that happen, particularly when my tractor was brand new, and right after I changed the filter and fluid at 50 hours. In both cases, it soon went away.

I have always assumed it was due to a little bit of air being trapped in the system that soon worked itself out.

 

[SnowRidge]

Re: Rock\'n Tractor

I just reread your post. For some reason I initially thought you said you bought your machine new six months ago. If that is not the case, you may have a worn part in the valving of the 3PH mechanism, and it may not be simply air in the system.

I saw the same thing happen to a friend of mine who bought a grey market Mitsubishi. In his case, the bouncing only occurred when the 3PH was carrying substantial weight. If I recall correctly, the repair was rather expensive because of the labor involved.

 

[frank_f15]

Re: Rock\'n Tractor

</font><font color="blue" class="small">( I have only owned the machine a short time, 6 mos, and have never used anything with the three point. )</font>
QUESTION! IS THE TRACTOR NEW? and you have had it for 6 mo. or is it used? if it is new talk to the dealer. sounds like a valve problem

 

[slowzuki]

Re: Rock\'n Tractor

Hello,

If it isn't air, it is just the feedback linkage on the 3 point. Nothing broken, just needs adjustment.

What happens is the position control watches the hitch location and corrects it to match the lever. If it gets too highs it bleeds to let it drop and if it gets too low it raises it back up. When out of adjustment this can form a cycle or feedback loop where it is still telling it to raise when it already has then it tells it to lower once it raised cause it overshot the mark.

 

[dingleberry]

Re: Rock\'n Tractor

Appreciate the input so far. THe tractor is not new, far from it. It is a 1982 Ford 1700 4X4 with 3800 hours. It was used almost exclusively as a backhoe. It never did this before when I used it. I am having a hard time tracing when the problem started because when I bought the box blade I brought it home and before I ever hooked it up, I drained and serviced the hydraulic system. I did not have the BB on before I serviced it so I am not sure if the problem could be air, plugged filter or what.

Please keep the input coming.

D

 

[KiotiJohn]

Re: Rock\'n Tractor

Well since you serviced the tractor have you checked the level of fluid again to make sure that it didn't change after you started running it? Probably not the problem, but it's a good idea to recheck after a few hours of use.
Raise the FEL, run it through all it's functions, and power it back to the ground and then put it in float, letting it sit on the ground.
Now, run the 3pt up and down a few times, and then put it all the way down, let the tractor run for a few minutes. This sometimes will bleed air out if there's some in it. If you have a seal in a cylinder that's not seating properly, you could be dragging air into the system while operating that cylinder.
There are several causes of this up/down motion, and the adjustment of the hitch that was metioned is but one of them. A worn pump that's trying to maintain the flow is another. Air in the system, yet another. A partially blocked hose/fitting is another possibility. Are you sure you cleaned the hydro filter out completely? Change any hydro filter that you may have? I'm not sure what's on that tractor, but for sure there's at least a screen, and maybe a transmission filter. John

 

[dingleberry]

Re: Rock\'n Tractor

kiotijohn,
thanks for your input I tried cycling through the loader operation, but I will try again with the loader in float and operating the 3 pt. Yes, I have a manual and I am sure I got all of the hydraulic system. It just has the one screen. Anyway to check the performance of the pump?? 3800 hours of backhoe use would wear me out too. /forums/images/graemlins/frown.gif

D

 

[slowzuki]

Re: Rock\'n Tractor

Not too likely a worn pump as he said it happens more aggressively at high rpm. This indicates the pump is supplying good pressure and flow.

A really bad set of seals in the piston that pushes the rocker shaft could do it too.

Ken