Got looking at the water pump on my vanagon, and noticed that there is no longer a plastic plug on the bottom where the weep-hole is. My recollection was that there used to be one, then I got looking at some other motors/waterpumps and discovered they don't have them either. No leakage at this time, but it seems like a finger-sized opening would be inviting problems for grit, etc, to get into the pump. Is it necessary? Are replacements available someplace? or is it just a figment of my aged imagination?