The "nasty black stuff" is the graphite lubricant. The reason that it is
leaking is a bad tach drive seal in the tach drive adapter on the back of
your engine. This lets the engine oil wash the Black stuff thru the tach
drive housing. The housing should not leak under normal conditions so I'd
also check to see if the housing has a hole worn in the side.


--
Cy Galley - Chair,
AirVenture Emergency Aircraft Repair
A Service Project of Chapter 75
EAA Safety Programs Editor - TC
EAA Sport Pilot


RonLee" wrote in message
...
My tach cable housing (Lycoming) leaks nasty black stuff so I cleaned
and dried it. What is the best lubricant to use? Particularly one that
does not deteriorate and leak through the housing. What about a
covering for the housing to prevent the leaking?