We recently rebuilt the e16 engine in our 1987 Sentra GXE. Its harmonic balancer simply sheared off and the replacement balancer and timing gear literally ate up the end of the crank. Its all rebuilt and with a new timing gear, guide disks and balancer it seems to run when it feels like it! However we've noticed a seal behind the timing gear that doesn't actually seal anything! There is an end plate casting that mounts to the block around the crack shaft, in it is a seal behind the timing gear and the timing belt guide disk (which is also loose and rattles). The seal looks like it should contact the crank shaft or a sleeve on the crank but there is, and was, nothing there. Could we be missing some part that secures the timing belt guide plate behind the timing gear and that would take up the 1/4" radius to the inside diameter of this seal? I've only noticed a very minor drip of oil that looks like black graphite grease. The crank's main seal is further into the engine and is in place. This odd non sealing seal seems usless, but I don't think the timing belt guide disk should be loose and rattling.