1990 300ZX NA - Slow oil leak near oil pan and transmission

[loopster1556]

Hello guys,

I'm just looking for insight as to possible causes for a very slow oil leak situated at the back of the oil pan where the transmission begins. Please excuse my poor choice of explanations, I am new to the world of cars and trying to troubleshoot and fix as much as I can myself. Attached is a picture where you can see a little droplet of oil forming. It does not seem to come from the oil plug or oil filter. It seems to be right on seam of the transmission. Is that a gasket leak?



Feel free to ask me any questions that may help you troubleshoot this correctly as I wouldn't be sure what is relevant.

Any insight from you experts is most welcome.


Thank you

Louis

[itsa300zx]

Rear main seal would be my guess. Should be a regular maintenance item during clutch replacement.

[loopster1556]

Thank you for the quick response. If I understand correctly from research and videos, in order to access the rear main seal you have to remove the transmission and the clutch, which gives you access correct?

Also, if there is a slight grind between 1 and 2, could the clutch be the culprit? I read that changing the transmission fluid and bleeding the clutch system is a good thing to do as well. (I replaced the transmission fluid last summer). I'm asking because i'm trying to see if this would all be related somehow and trying to see what I should replace while the transmission is pulled out.

Any additional suggestions / insight welcome.

Louis

[itsa300zx]

Correct, trans and clutch needs to be removed to access RMS.

Slight grind MIGHT be related to clutch, but more likely trans syncros. Try redline MT 90 trans fluid, it help solve my 4th gears slight grind. How old/mileage on the current clutch?

[loopster1556]

Unfortunately, I don't have the age / usage of the clutch at the moment, I will try to see if I can contact the previous owner to know. I have heard good things about redline MT90 so I will give that a go.

Maybe 1 more question; do you know if using some sort of oil additive such as no leak engine oil stop leak http://www.goldeagle.com/product/no-lea ... -stop-leak could be useful here, between now and when i get the seal repaired? It does say it works for rear main seals, but I don't want to make it worse by adding a foreing agent in the mix.

Thanks again for your help. It's much appreciated

Louis

[DCaff300ZX]

I would NOT use any type of additive of that type on your engine, both because those products often lead to other issues and mostly because having this small of a main leak is not a big deal other than the drip mess. I let mine go for almost a month (3 drips a night) before I got my engine and trans work done. Put a piece of cardboard under it if the mess is a problem on your driveway, and get the work done as soon as you can and you'll be fine...checking your engine oil level religiously the whole time of course!
You will want to replace all of the clutch fluid of course (don't save the old and reuse), and be aware that there are two bleed points in the system to deal with- a common DIY scenario that results in no clutch, and another frantic post on that issue

[loopster1556]

LOL - ok thank you, this is the type of confirmation I was looking for. You're correct, it's a very slow leak, and I do check the oil level regularly. I will make sure to do my research to bleed the clutch properly and use redline MT 90.

If you don't mind me asking... I don't have the tools at home to remove the transmission. If I take it to the shop, would there be other work / inspection I should have them do while the transmission is out?

Thank you for your assistance.

[NolimitZ32]

Depending on the condition of your clutch it is always an item to look at replacing, if that's being done then flywheel resurfacing is almost a must. The only other thing I can think of would be to replace your clutch fork and pivot to the HD ones. Also if you are looking to do some deletes I would think this would be a good time to delete your EGR. I'm sure I'm missing something, I'll let others chime in.

[loopster1556]

Thanks NoLimit, i just learned what deleting my EGR means

[DCaff300ZX]

I think NoLimit covered it pretty well, although some also remove the two-bleeder point clutch line and use a Z-1 one bleeder line to make the bleeding easier. I bought one but my Z guy didn't use it, preferring the OEM setup...

[loopster1556]

Ok thx Dcaff. I also wanted to ask you, would you replace both the transmission and differential with MT90? Also, from the sound of it, bleeding the system is not something you can do at home? I ask because I changed both the transmission and differential fluids last summer. Aside from a vaccum pump, we didn't need anything special. Maybe I need to watch more videos too

And while i'm at it, MT-90 redline, is that a unique product or are there 75 different versions of it and you have to pick the product that applies to your can specs?

Thanks again for answering my nagging questions

Louis

[DCaff300ZX]

No problem with the questions, it's what we are here for and enjoy helping out with.
I would go ahead with the Redline fluid as I have heard nothing but good from it, I have never needed it as my trans (knock on wood) works perfectly and especially now after a full shifter rebuild and new HD internals with the new upgrade clutch. As far as I know the MT-90 covers any version issues as it is 90 weight oil for transmissions and rear diffs, Redline product.
As for bleeding you can do it with help from a friend to actuate the clutch pedal same as brakes, or use the vacuum type bleeding pumps...just keeping in mind that you have the two bleed points to hit not one. Do the closest first, then furthest to finish.

[itsa300zx]

Ok thx Dcaff. I also wanted to ask you, would you replace both the transmission and differential with MT90? Also, from the sound of it, bleeding the system is not something you can do at home? I ask because I changed both the transmission and differential fluids last summer. Aside from a vaccum pump, we didn't need anything special. Maybe I need to watch more videos too

And while i'm at it, MT-90 redline, is that a unique product or are there 75 different versions of it and you have to pick the product that applies to your can specs?

Thanks again for answering my nagging questions

Louis

MT90 in the trans
75W90 in the Diff

[loopster1556]

Ok will do, thank you both for the clarification