All too often, the shaft has wear in it from the old seal rubbing on it. In addition, there is play in both the front and rear bearings. Combined, the pump leaks no matter what you do.

The pumps will interchange if the year is close. Both tractors use the same GPM rating but Case used pumps from different manufacturers in different years. In some models, the suction line was a hose that went from the pump to the reservoir but in other years, a steel line was used with very short hose sections on the ends to make the joints.

Therefore, some pumps had threaded inlet ports designed to take O-ring fittings while others had a hard, curved pipe swaged into the casting. Of course, you can change the supply lines or fittings to make another pump work.

Case tractors don't use "hydraulic oil", they use "motor oil". Yes, you can use a straight grade 30 weight oil but 20W40 or 20W50 are often used in predominatly warm climates and 15W30 when the temps fall below freezing. Shell's Rotella T or a direct equivalent is the oil of choice.

And no, there is nothing that you should adjust. Relief pressures were set at the factory and should not be altered, especially by persons who have no hydraulic background or the tools to carry out this work properly.

The reason your pump leaks under load is simple. When the tractor is started, all the pump is doing is to circulate the oil through the system. Pressure is minimal because there is no restriction. Once you begin to operate either the loader or the hoe, system pressures rise rapidly. If you bottom out a cylinder, then you will hear the relief valve squeal and that means the pump is now putting out 2100 PSI.

Either buy a new pump from an aftermarket seller such as Grainger or get a good used pump from another Case tractor. Any 200, 400 or 600 series tractor can be a donor.

I have a Case 646 tractor/endloader, Tractor Serial #9698629. I'm looking to replace the hydraulic pump, which has the numbers S15S5EH22R on it. I've been told in the past that the Case dealer thinks its a Borg Warner.

Does anyone know of a more cost effective pump, than the one from the dealer (last time I checked they wanted about $600 for one.)

Thanks in advance for your help.

Greg

P.S. The tractor has been loosing power, any other ideas besides the pump? I'm running 20 weight oil in the hydraulic system.

I have a Borg Warner hydrulicnpump No.S15S5EH22A.I need the repair kit and woodruff key for this unit, It is in a Case 646 loader Sn. No. 9744939. Please let me know where I can get these parts. Thank you. Hubert Kieffer