Join Date: Jun 2006
Location: Hillsboro Oregon
Mentioned: 2 Post(s)
Quoted: 281 Post(s)
Is this an open center 1680 with the small gear pump on the left hanging below the reservoir? If so, there is a block bolted to that bracket with a plug on top. That plug is the relief valving. It is difficult to shim, and near impossible to afford a new one. The spring weakens over time lowering the pressure.
On that same style 1680, there is a screen up by the cab next to the entry door. It is inline with the pressure line. It may be plugged.
The best investment I ever made on the hydraulics of the combine, was to put a gauge in the pressure line just off the pump. Now I have an instant diagnosis tool that will tell me with reasonable accuracy where I need to look for problems should they come up.
The gear pump, if it is the type you have, is available off the shelf at most hydraulic sales counters. There are numbers stamped into the pump that you will need. It is a tapered shaft design, but common taper.
I replaced the relief with an off the shelf unit made by Prince for about $69 or so. At that same time, since I was making a couple hoses to hook the relief valve up, I installed the gauge. Granted I need someone in the cab to hit the switches to activate circuits so I can read the gauge, but that is no problem as the truck driver is never far away.
If you have the newer 1680, I'm not much help.