Tom

Tom,

Q I had the front and back main seals replaced on my Jeep Cherokee two

weeks ago (it has a straight six-cylinder engine). Both seals are leaking
again! What could be causing the problem—from a mechanical point of
view?

Sam—Dallas, Texas

Sam,

A What other point of view might you expect from me? Metaphysical?

Psychological? Lie down on a couch and tell me about your seal problem . . .
ommmmmm . . .

All kidding aside, I would make sure it is the same leak. A great way
to make absolutely sure is to conduct an oil leak dye test. During this
procedure, the technician adds a fluorescent dye to the engine oil, and the
engine is then run for a few days. At this point, the vehicle is put up on a lift
and the questionable area is exposed to an ultraviolet light. The leak can
easily be located, as it will show up in a bright yellow color under the light.
Another possibility could be that either the PCV valve or the crankcase
ventilation system is not operating properly due to sludge plugging it up.
This problem can cause excessive crankcase pressure and oil seal leakage.

If the vehicle is of high mileage, check the crankshaft surfaces upon
which the front and rear main seals ride. Make sure there isn’t any excessive
wear or scoring, as this would result in leakage as well. If wear on the front
of the crank is evident, there are sleeve kits that can be installed to take up
the gap from the wear, restoring the sealing surface, and most important,
averting replacing the crank.