Tractor Repair: Farmall 806 diesel with a JD 148 bucket loader, farmall 806, hydraulic flow

Question
The tractor is around a 1968 with a rebuild motor.  My dad used this tractor many years before he passed and I have taken over some of the farm work.  About a month ago I noticed the tractor having trouble lifting; it has been working slowly for a while but since it has gotten colder it has gotten worse (we live in WI if that helps at all).  The bucket on the tractor will lift fine empty but putting anything in it, even something light (a bucket of snow), it takes a long time to lift.  This happens after the tractor has been warmed up.  I have been told that I could have ice in the lines, the relief valve under the seat could be wearing out, or the main pump could be going.  The three points work OK but bucket lifts slow.  Do you have any thoughts?  Thank you.

Answer
Hello,

  I am in WI also, so I know the weather conditions you are dealing with.  If a filter is getting restricted with ice crystals or dirt, the hydraulics will get slow and may even be jerky, but will still have enough power to lift.  The fact that you say it happens when the tractor warms up makes it sound like the pump is worn out.  As the oil warms up it gets thinner, so it will bypass inside the pump easier than cold oil.  If a relief is bad, the hydraulics would be weak, but temperature would not make any difference.   If you haven't changed fluid and filter in a long time, then it should be changed anyway, but it may not solve the problem.  The pump should be tested with a hydraulic flow rater which will determine it's condition by testing the flow under pressure.  If the flow at 1200 psi is at least 10% less than the flow at no pressure, then the pump is worn out and the oil is bypassing internally.

              Good luck,

                     Arnie