My 86 420 SEL has a constant tapping noise from the top end of the engine. By looking through the oil cap hole I can see that my camshaft oiler plastic mount is cracked. I suspect that the same is true of the other side of the engine. The camshaft has no grooves in it and the lobes are shiny(normal?). Will these camshaft oilers being faulty effect the oil pressure ??? My gauge reads perfectly all the time according to my manual. The coolant temp is also normal all the time. The engine still runs very smoothly. The reason why I think the plastic mounts are just leaking and are probably not the main source of the problem is because the engine oil pressure is perfect and the top end of the motor is getting oil. Is it fair to say that the noise may be a faulty lifter or rocker arm ? Any input or info would be appreciated. THANKS