Ok…I’m posting this here, since all the information I found on this seemed disparate throughout the forum and the thread refers to the leak behind the oil cooler.
I noticed during my last oil change there was some oil residue/sludge accumulating around the edge and underside of the oil pan and subsequently a complaint filed by the boss there was oil on the driveway. I checked it out and couldn’t find the source, so I had to clean out all the Northeast winter road filth that had built up and wait. The car sat for about half a day with no sign of a leak. I started the car up and found the leak coming from behind the oil cooler, under pressure. So…scheduled during the next oil change was an o-ring replacement as well. The FSM was minimal help, and these forums proved to be a great source. I found the part number for the oil cooler o-ring gasket (B1304-43U00) in this thread. This part required a call to three different dealerships, but I finally found one that had it. Interestingly, when I got to the parts counter, the guy there told me there was no such part for a 2003 Maxima; then ironically, a tech walked up for something and confirmed there is with the qualifier statement, “Of course there is, we change them all the time!” That really made me feel good about the durability of the gasket.
Anyhow, below are a few pictures of during and after…didn’t think to take before pictures. The first shows the oil cooler removed and in its natural 130k mile condition. I’ve included comments to help novices like myself. The hose seen on the left is one of the coolant lines. It was replaced during an oil pan gasket replacement. It only needed to be replaced because it was stabbed by a snapped drill bit while trying to drill out a bolt whose head broke off. You will see later I replaced the second hose during this repair…figured why not since I am disturbing it anyhow…and replaced the clips too with stainless steel hose clamps. The second picture is the oil cooler wiped down and cleaned up. The third picture shows where it is located and points out the coolant supply and return lines. The last picture (no comments on the belt please, it will be changed very soon) is the oil cooler returned to its place in the wild with the 23mm bolt, torqued just right. You can see the SS hose clamps. I decided to use these because I like them better than the OEM clamps.
During the work expect to lose the coolant (about a gallon in my case) unless you plug both ends. I decided to let it drain and replace with fresh, since I reused what was recovered from the oil pan fiasco. Tools and parts needed:
10mm socket (to remove the wheel well shield)
Phillips screwdriver (t o remove the wheel well shield)
Slotted screwdriver (for the hose clamps)
Approx. 4” long x ½” OD hose (will verify the ID)
(2) SS hose clamps (purchased from Lowes for about $1.50, 7/16” to 29/32” size).
23mm deep socket (for the oil cooler bolt)
(1) Oil cooler o-ring gasket (p/n: B1304-43U00)
Coolant (if needed)
Oil (will be needed)
Oil filter (I reused my old one…j/k)
Pliers (to remove the OEM hose clips)