I've heard of plenty of rear main seals leaking in Magnas, but how common is a leak from the front crank seal?

I've got a VERY slow leak, which I've been able to trace as far as somewhere behind the crank pulley, which pretty much pegs it as the front seal. By slow, I mean just enough to leave a film on the bottom of the sump pan after about 2000km.

The engine's from a 2004 TL, with just under 108,000km.

Have you had the timing belt and seals changed? Chances are the crank seal was installed incorrectly. Pull the cam belt cover off, and see if there is oil on the belt. If not, leave it, but if the back of the belt is oily it needs to be fixed. If you still have the original belt on, belt change time is a good time to see what is going on.

I changed the belt at 98,000. It's still got all it's original oil seals, which we checked when we changed the belt. They were all bone dry, but that only means that they were ok 10,000 ago. It really is the slowest of slow leaks - normally I wouldn't worry, but it's the sort of thing that I'll always be thinking about. If it does need doing, I may as well get everything done - water pump, both cam seals and the crank seal.

Make a note to change the 20 or 30 bucks worth of seals next time you do a timing belt - its like water pumps, cheap insurance against having to the job all over again! :)