In regards to the confusion about the O-ring part numbers and some OEM ones not fitting - the actual part number for the older style (smaller and orange colored) O-rings is B1304-43U00. This part has been superseded by the 21304-JA11A which is black and too big to make a good seal on the older G's. The new part automatically gets ordered when you go ask for the oil cooler O-ring at the dealership, so you'd need to specify this outdated part number.

The Fel-Pro replacement on rockauto (same as the amazon link a few posts above) is the only aftermarker one I've found that fits for those with the older and smaller O-rings.

For reference - I have an 03 sedan and got stuck ordering multiple replacements (both OEM and aftermarket) before realizing that this was the case.

Further confirmation of this can be found on Infiniti's part lookup here: parts.infinitiusa.com

Sorry to anyone getting notifications on a years-old thread. I hope this info helps any of you guys still working on G's!

 

As common as this repair is, it's hard to believe Nissan or Infiniti dealers will have the old part in stock. At the time Nissan superseded the old part, as inexpensive as they are, they probably tossed the old ones in the garbage. Even if you order the old p/n, they'll give you the right or current one. Now, aftermarket suppliers may have copied the old design and are still supplying it and the thing is, it will work for a while, possibly quite a while. I replaced mine but it lasted close to 100k miles and 10 years.

 

Hey..I have an 08 G35X as well and when I bought this O ring from dealer it was the larger one that fits on the outside of the housing and it has the same part number. The one that was originally inside of the cooler was actually the smaller one that fits on the inside of the grove. Was yours the smaller O ring or the larger one? Does it make a difference which one needs to be used..?

 

There's only (1) o-ring and I can't remember specifically where it was positioned. It will only fit in one location though.

 

I note the FSM doesn't indicate that oil needs to be drained to R&R the cooler or replace the O-ring, That makes sense to me, given the oil cooler and filter are above the level of oil I'd expect in the crankcase.

It does indicate draining the cooling system, but also indicates coolant hoses can be pinched in lieu of draining cooling system.

Question: Has anyone replaced the O-ring without draining the oil?

 

Not sure, I'd suggest trying it without draining oil and just keep a collection pan under that spot in case it does spill out oil.

 

As it turns out the car was ready for an oil change, so I drained the oil anyway. Picked up a Fel-Pro #72493 from my local NAPA. It was obvious the Fel-Pro part was taller in cross-section, so I measured both of them. The old one was 0.0154" / 3.91mm tall, while the Fel-Pro part is 0.195" / 4.95mm tall. The old one was still plenty pliable, while the Fel-Pro part appeared to be firmer / higher durometer. Between the extra thickness and firmness, I suspect this will seal well and fix the problem.

Replaced it without removing the coolant lines - I just pulled it far enough out to remove the old ring and insert the new one. Tightened it up to 36 ft lbs and voila, all fixed.

p.s. I'm planning on re-torquing the Connector Bolt the next time I change oil.