Engine/Transmission (1998.5 - 2002) Tracking down oil leak

[woodtrucker]

Second time I've changed oil and only got 2 gallons out which means I'm losing 1 gallon between changes so I better try to fix it.
best I can tell I see the block is wet with oil up behind the starter. Is the tappet most likely going to leak that far back on block? Anybody got any advice here? I don't think it would be rear main but it is leaking down to bottom of bell housing so....
Thanks.

 

[SAndreasen]

My guess is the tappet cover

 

[klcammie]

I second that. Tappet cover gasket is "easy" to change, the hard part is getting to it. Lots of stuff to move. When I did my 01 it took 6-8 hours. Course I was not in a hurry. If you look at first two pix you can see how much oil leaked. The last pix shows the broken gasket.