 I think the seals on the pump might be allowing it so suck in air which is why the oil is foaming, and then the cintered vent brass is clogged so the air cannot escape (though it would probably overpower the tiny vent anyway). Or, the oil you are using is not the quality and type called for and it is foaming up as it runs through and gets whipped up by those gear teeth. Make doubly sure you are using the JD oil called out as "For Use in Power Steering Systems prior to 1960". Unscrew the dip stick and see if it still "boils" over using this oil. If it does, you can try to lay some air pressure on the dipstick hole and hope to force some oil out of the problem seal or joint so you can find the suction leak. If it is leaking out of the frontmost fan shaft pump seal, you might get lucky and see the drip, but the odds are 50:50 that it is leaking out of the rear most seal which you cannot see. It could even be leaking at either end joint of the suction pipe. If it were me, if it's still sucking air after an oil upgrade, I would pull the pump. It probably deserves new seals by now. Understand that the new seals are offered as two seals front and two seals back to replace the original chevron double-lipped seals. Frank
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