I have a 92 300SD and 9k on a rebuild engine, by a shop that when out of bussines allready. Some times I hear some knoking after car been running for a while, knoking is not loud and does not do it frequently, every other day maybe. Is there some thing that I need to check to prevent any further damage? or wait for sound to be came more frequently?. Also once I run car on high speed, oil light come ON, also not all time light will come ON, but oil pressure gauge is normal and have good fresh oil 15/40 Castrol. Any advise