Truck Repair: 1998 Nissan Frontier Oil Leak, nissan frontier, frontier oil

Question
I have a 1998 Nissan Frontier 2x4 truck 4 cylinder and have owned it since I bought it new back in Oct 1998.  I regurlarly change the oil and have it tuned up as well.  I have not had any problems with the truck since I owned it.

But, I have noticed a leak on the passenger side of my 1998 Nissan Frontier 2x4 truck 4 cylinder.  The oil spot on the ground when I see it is approximately 4-6 inches in diameter.  The service station where I take it in for oil changes stated that this was a result of oil build on the skid plate after an oil change and that this was the cause of the oil dripping.

About 3 weeks ago I took my truck in to the Nissan dealership to check it out.  They said that the oil pump gasket was bad and this was the cause of the oil leak and at that time they replaced it.  So for the next two weeks there was no oil leak.  

Then 3 days ago the tempature got colder and I notice an oil leak again in the same spot on the ground as before.

Any thoughts as what may be causing this?

Thanks for your time and help.

Gene

Answer
Hi Gene,
First of all, I doubt that either of those people are trying to scam you.
I have seen oil build up in the grooves of a skid plate when the oil is drained. I try real hard to deflect the oil so it won't collect on the skid plates, knowing that they will drip for days.
The dealership possibly did find oil from the pump, and probably cleaned the skid plate while working on it.
But it is possible that the oil is coming from higher up, running down across the oil pump area, and collecting on the skid plate. That would explain why it seemed fixed for a few days.
I feel there is a need to search a little harder.
The best way I have found is to get in a real dark place, like a dark garage, and use some good directional light source and a mirror.
Don't use a cheap plastic drop light that you can't see past because the plastic is so bright.
Look up near the bottom of the head, and valve cover.
Look at the oil pressure sending unit, and the pcv valve.
Oil pan gasket, and timing chain cover, as well as the front crankshaft seal are other possibilities.

I immagine if you take it back to either of those places, and explain that the leak continues, they might search better.

Van