Abstract: An oil reservoir for a hydraulic steering system is provided with a venting means comprising a sequence of passages from an inner protective pipe movably guided with concentric spacing on a bolt fixed to an oil reservoir housing. The concentric spacing is part of the venting passage wherein venting passes through a groove on the bolt into a venting cap. The venting cap is threadedly carried on a threaded section of the bolt through which the groove passes and effects a portion of the venting passage means. A nut carried by the venting cap effects threaded coaction and may itself have a venting groove. The protective pipe is biased into sealing engagement with the lid by a compression spring. A special construction permits ease of lid removal in conjunction with oil level indicator means.