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RMS or Half Moon Leak?

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Old 07-31-2022, 02:47 PM
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RMS or Half Moon Leak?

Hey guys,

I have had a minor oil leak coming from the front and rear half moon seals locations over the past few months. Little pools here and there but nothing significant. Recently as my commute as increased by around 40-60 miles, I noticed my oil pressure light would come on as i was waiting at a stop light, it would blink repeatedly as my RPM dipped below 500-600 RPM. I poured in about 1-2 quarts thinking my oil was low, but when i went to go to my car later that day, i found a huge puddle of oil underneath my car. Could it be that that the RMS has gone bad?

I checked the dipstick shortly after i found the pool of oil and it marked full as can be. No significant oil leaks since then (besides the typical drops that im used too), but is this a sign the RMS has gone bad? I have read a few posts already stating that the RMS can go bad if the engine is overfilled with oil and i suspect that is what has happened.,, I took it out for a drive earlier today and after driving for around 10 miles or so, there was some smoke coming from the area the middle of the engine bay from where the engine touches the transmission.

How can i determine if the RMS has gone bad or if its the half moon seal without dropping the transmission?
Also i read that the 2 o-rings within the upper oil pan can lead to the low oil pressure light coming on...is there any validity to that?

Would love to get some input from the OGs that still lurk here before i go ahead and start planning for this headache of a job
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Old 08-01-2022, 03:38 AM
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Based specifically on what you’ve described, it reads like you may have, for a moment, had a brain-fart.

I think I’m reading that you over-filled the crankcase, experienced an oil leak, after which, the leak has resolved … is that correct?

If that’s truly the case, my recommendations would be:

(1) Check your oil level regularly and following the proper process (i.e. using the dipstick). An illuminated oil light is never a positive sign.

(2) Thoroughly clean your engine or at least all areas soiled by the leak, top of engine to bottom of engine. The leak actually may not have been an oil pan or rear main leak in the first place.

(3) Keep an eye on things (oil level, engine cleanliness, leaks on the floor). If a leak returns you’ll be much more clearly able to point points it’s origin.
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Old 08-01-2022, 09:44 AM
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Apparently you over filled your engine .
You added 1 to 2 more quarts than it's designed to hold.
That amount of extra oil creates problems.
Please drain all the oil. Then pour only 4 quarts back in. Store the rest til you need it.
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Old 08-01-2022, 07:05 PM
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Yes, with full confidence, i had a brain fart and overfilled my crankcase with oil

Thank you Turbo & JvG for the advice. I plan on doing the oil change this weekend and cleaning out the engine bay to try to locate the leak. Ill update when i can. Keeping my fingers crossed the RMS has not gone bad
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Old 09-08-2022, 08:45 AM
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Finally got around to doing this job. I ended up doing the oil change and the leaks were still there. I decided to bite the bullet and remove the upper oil pan to get it resealed. Job took me around 20 hours across 3 days from start to finish. The hardest part for me was getting the upper oil pan back in place as the dowels on the block were not going in smoothly. I used some RTV to keep the 2 o-rings & the half moon seals in place as the pan was being installed.

Both of the half moon seals (front and rear) were broken and extremely brittle. I referenced the FSM and this thread ( https://maxima.org/forums/4th-genera...n-removal.html ) for the procedure. The smoke that i was seeing prior to dropping the oil pan is now gone, unfortunately i dont think i used enough RTV black in some portions and now i have 2 small leaks coming from somewhere.

For anyone trying to do this job on their own, it really isnt that bad. Hardest part is getting those damn studs off the y-pipe (the ones from the firewall). Next up is tackling that steering rack.
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