Nissan 3.5; neighbor complained that the check engine light was on. P0011. timing off on bank 1. hmmmm. pulled dipstick. 4 quarts low!!!
It was an easy repair: replace the o ring between the oil cooler and the block. supposedly book time is 1.2 hours. didn't take half that.
My replacement 5.4 is permanently noisey from that happening. Oil cooler went bad and it dumped 6 quarts of oil into both the coolant and out of the cooler itself while driving. Never had the oil light come on, but it was realllll low.
I acquired a free 03 Maxima with a 3.5L with the infamous busted radiator/tie bar support. When I got it the 3.5 was dangerously low on oil. I added 3.5 qts! There are a couple of leaks. One is the cam sensor o ring. Another is from the pan area. I assumed its the drain bolt washer. Could that possibly the o ring you describe??
I acquired a free 03 Maxima with a 3.5L with the infamous busted radiator/tie bar support. When I got it the 3.5 was dangerously low on oil. I added 3.5 qts! There are a couple of leaks. One is the cam sensor o ring. Another is from the pan area. I assumed its the drain bolt washer. Could that possibly the o ring you describe??
The O-ring is behind the "oil cooler"......the round thingy that the oil filter screws onto. You remove the filter, then there's a big nut behind it (if memory serves correctly). The housing (oil cooler) is then able to move away from the block. There is a big O-ring behind it where it mates to the block. They tend to start leaking above 100k miles. Get the replacement from the dealer. They've been redesigned over the years and I think I only paid about $8 for it.
Edit: There are two rubber hoses that connect to the oil cooler. They contain coolant. Be careful with them..........unless you're replacing them also. Mine were oil saturated from the leaking O-ring, so I replaced mine.