Had the valve cover gaskets done on my 2003 G35 in February 2020. Car had 155,000 miles on it. A few days later I noticed a few spots on the ground under the car. Took it back. Was told that it was a pinched o-ring on the cam position sensor. Took it home. Couple days later noticed drips again. Took it back. They ran dye and said the sensor was still leaking so they replaced the o-ring with a larger one. Went 6 days before I saw a drip again. What ever is leaking, it's leaking very slowly. I've looked underneath as best I can (not a fan of going under the car when the only thing between me and certain death is a pair of plastic ramps) and as far as I can tell the oil filter and surrounding area looks dry. I see oil on the bottom of the bell housing but can't see if that is the source of the leak or if it's higher up and running down to that point. They said to bring it back in again but I'm starting to wonder if they'll ever find the source. I've used these guys for several years and never had an issue with their work. This can't be residual oil from the valve cover leak as that was 7 months ago. Any ideas as to what might be causing this? I hate to have to take it to the dealer. There is a Nissan not far from me.

 

Get an inspection mirror and a good flashlight so you can look around the engine from the top to determine for yourself where the leak is coming from.

Wipe everything down good with a rag before you start so you will be better able to tell where exactly it's coming from. A rag taped to a stick will be your friend, helps a ton trying to wipe down oil from really tight space.

DONT CATCH THE RAG ON FIRE FROM HOT EXHAUST COMPONENTS!!!

 

I checked from the top as best I could. I don't see any traces of oil. I even used my hand to feel around the area of the cam position sensors and it feels bone dry. I still see oil at the bottom of the bell housing. I'm worried it might be a main seal but if that were the case I don't think it would have taken 6 days to see oil down there.

 

Assuming I have a bad seal, I called my local Nissan dealership and got a quote for replacing the rear seal. Asked about the front seal as well and they said the labor would be the same whether they did one or both at the same time. Does that make sense?

 

You're going to need to get a look from under the car to find a slow leak like that. Use the splash guard as a guide to help you find the leak. Check the power steering rack and lines.

The rhino ramps I have from AutoZone are rated to 16,000 pounds. No way a G35 will ever come close to that weight. Whenever I put my car on them, I set the e-brake and put a block behind the rear tire just for good measure. Remember to wear safety glasses when under the car!

 

I have my trans pulled right now and the rear main seal is leaking. It appears to only be a leak in the housing of the seal resulting in a slow leak exactly like you're describing.

 

I'm pretty sure my rear seal is leaking too. If the labor charge is the same to replace both rear and front seals at the same time, I would have them do both. Just thought it strange since I thought the front seal would add more hours to the job.

 

My best guess for the front seal is that the dealership is going to drop the entire upper oil pan. That should make it easy to service both seals.

 

So we're not talking crank seal here, correct?

 

Well the front upper oil pan seal. I’m not 100% sure on the crank seal. I was assuming that’s what the dealership was talking about replacing.

 

Yes I believe you're correct. I spoke to my indie first and mentioned the rear seal and the CRANK seal He said both are big jobs. One needed the transmission dropped the other needed the engine pulled. Then I called the dealer for a price but I mentioned FRONT seal not crank seal. That's why they said they could do both for no additional labor charge. My mistake. Thanks for your input. Helped me realize where I messed up.

 

Yes the dealership will drop the UPPER pan when doing the RMS, that's how the steps are listed in the FSM. It's an incredibly labor intensive repair (that method) and you're better off just going to an independent shop that will remove just the tranny, then pry out the RMS housing and replace just that component.

You'll be paying for close to 20 hours of labor at Nissan, probably 10-12 hours at an independent shop. At $150/hr you do the math... my guess is Nissan quotes you $2500 - $3000

Independent shop will pull the tranny, neither requires the engine to be pulled. Nissan will have to install an engine bar to support it from the top, then remove the entire front suspension and engine subframe, then most of the front of the engine components.

Personally I'd just pry out the RMS and replace just that component, no reason to rip the engine apart.

 

My indie said that if it was the rear seal it would be around $1000 so I scheduled a drop off day so they could look at it. Then I called the dealer to get a price on rear seal replacement. They told me $1300. I asked about the front seal and they said the labor would be the same with only a small additional amount for the part for the front. I assume they're talking about the front oil pan gasket. They did say they drop the upper pan. After I dropped it at my indie's, he called later and confirmed that it is the rear seal that is leaking and quoted me $1300. Not sure why it jumped $300. He had the car already so I said go ahead and get it taken care of. He also will be dropping the upper pan. I was surprised at how low the dealer's quote was but it was just over the phone without ever seeing the car.
I'm hoping the crank seal isn't the next to go since it's probably made of the same material as the rear seal. If it does, is it as big a job as the rear seal? I notice the FSM does not require the engine to be pulled to do it. I could have sworn my indie said the engine had to come out if it was the crank seal. Maybe he misunderstood me. I'm going to ask him about that again when I pick it up later this week. After this repair I'm committed to at least another 3 years for this car. A 2003 with 156,000 miles and still runs amazing.

 

Here's where I get confused. My Chilton manual says to just pop out the rear crank seal with a screwdriver and put the new one in. However, the replacement I ordered from Z1 is the entire RMS with the crank seal built into the housing. So what I'm wondering is do you know a way to replace just the crank seal like my service manual says? If not, how do you replace the entire housing without rolling the upper oil pan seal as you slide the housing over the crank? Picture of my replacement for reference. ↓↓↓

 

The pan seal slides over that little groove on the bottom edge of the RMS, it slides on without too much hassle but yes you have to watch the rubber to make sure it is actually seating properly. I set the bottom part in first, then get it all started around the crank, then push the bottom in a little more then drive it all on flat.

The reason you can't do like the Haynes/Chilton explains is obvious when you look at that picture of your RMS, the seal is installed from the BACKSIDE of the housing, you cannot just pull it off and leave the housing in place like you can on a Toyota or most other vehicles. Either way the RMS housing has to be removed.

Yes you can pull the actual ring seal out of the housing once it's removed from the vehicle. It's fairly difficult though it's a very tight fit.