Help needed -- Northern Tool 37 ton log splitter

I have the same splitter and have replaced the control valve for the same reason as you. It is an internal leak, as that portion of the control valve is filled with grease normally, but will fill with oil when an internal seal gives up.

Mine was within the two year warranty, so they charged me for one shipped asap, then refunded the money when they got the old one back.

I had another major leak with mine this past week when the oil filter burst and puked-out all the oil. A real Exxon-Valdez moment.

It turned out the bypass valve inside the filter mount, which is supposed to open if the filter gets clogged, had dropped back to block off the return line completely. Can't figure out how the little bugger got bent and slipped through the hole. I think it must have been bent from day-one and finally came loose.

I'd contact NH anyway as if it a known problem they may warranty it.
Otherwise, take it apart, pull the spool out, and see if there is an oring in a groove inside the valve body casting.

The part was $151.81 with shipping. (Prince valve, part 778435) The warranty is 2 years, so you might be lucky.

I just spoke with Tim at Northstar. 1-800-270-0810. Very helpful guy. I told him about my burst oil filter and he wasn't at all surprised.

It happens that the bypass valve actually operates all the time with pulses in the system. It seems that the filter doesn't have the capacity that it needs, and is usually manifest by blowing out the oil filter gasket. The part that bent on mine used to be made of plastic but now is made of metal that still isn't up to the job. So, now the new splitters no longer come with a filter. The new splitters, as well as the old ones, have a 80 micron screen on the suction line. Because of that, and the fact that it is pulling oil from about 1/2" above the bottom of the tank, is enough that the manufacturer will warranty a pump without a filter in the system.

On another note, I asked him about my cylinder retract detent that doesn't stay put. He knows about that one too, and is sending me an upgrade kit for the valve that installs under that cap that's leaking on yours.

The valves used on the majority of splitters usually sell for about $70.00.

I have seen many articles advising against having ANY kind of intake screen between the tank and the pump inlet - arguement being that it's inherently a flow restriction and can cause a pressure drop at the pump intake, leading to cavitation in the pump, and subsequent pump damage, especially if the screen starts to get clogged... At the same time a filter screen that is large enough mesh to not be a flow restriction problem is relatively unlikely to stop particles that would be large enough to harm the pump.

Oil filters and heads that CAN handle the job are readily available on line or through your local hydraulic shop...

Gooserider