Thanks, I installed clear lines between the wvo filter and the valve switch and can see clearly that there is air being introduced before or at the filter. There are only 2-3 clamps between that point and the aux wvo tank, so unless the hose in that tank is above the oil level partially(I haven't tried more than 5 gallons in the 12 gallon tank) I don't know how this is happening. I've been using a vacuum pump to test it out though I think my stock pump could use an assist. I believe there are inline pumps I can buy and install...

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1984 190d 5 speed manual