Steering: Eaton Pump Reservoir Vent Question

[over50]

In the 59-64 manual for the Eaton power steering pump and reservoir, it talks about not tightening the cover wing nut too tight. This is related to a cover vent. Can someone explain how the vent works on this cover? There is a gasket, washer and the wing nut, which appears to seal to the cover.
Thanks
Norm

[Mike]

On my '64, there's a recess stamped into the lid around the stud; and a small hole drilled through the lid from the recess to the reservoir. I use a fender washer with a large rubber washer under it on the stud. These "roof over" the recess but don't block the small gap from the recess to the open air. The reservoir vents through the small hole, to the recess, and out through the gap. It's important not to use Ford parts, which are often included in rebuild kits, that cover the small hole or block the gap. Fords have a stack; and vent through the small fill cap.
I suppose if you used a thick rubber washer, and over tightened the wing nut, you could block the gap. That would seal the reservoir and allow pressure to build up, forcing fluid to leak somewhere.
Mike M.

[over50]

Mike - Thanks for the answer but I need a little more info. I see the recess and hole but my 1 inch diameter washer and gasket will seal against the top. You mentioned a fender washer. If I use a 2 inch diameter or larger washer, it will load on cover ridges farther out and leave a gap on one side that would vent. The washer in the shop manual picture doesn't look this large and a gasket isn't shown. Is this 2 inch diameter size washer/gasket what I need?
Thanks
Norm

[41 Frank]

My original washer measures 1 1/8" in diameter, it is about the same size as the rubber seal.