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Very large oil leak


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I found a oil trail down the street leading into my garage. Looked under my 240z and found a very large oil puddle coming from where the tranny and the engine meet. I believe its the rear main seal. If so do I need to remove the engine and tranny or can I just drop the tranny. I tried researching the proper steps on replacing the rear main seal but met with no luck. My Chiltons book says to remove engine.

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Remove the transmission and take a peek.

Rear main seal can be changed with the engine in the car.

BUT: If it's a really big leak, what have you done recently to the car?

Normally the rear main seal doesn't leak that badly or just start suddenly.

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haven"t done anything. Its been leaking a few drops for quite a while so I used stop leak and it did stop for sometime, but I guess the seal can only take so much. I'm pretty sure it's the seal. I never performed a big job like this before. looking forward to the challenge. once I remove the tranny is the seal on the tranny or on the engine?

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I had a leak before, it was located apparently from the same area as yours.

I've checked everything at the time and found it was coming from the window on the front of the engine on the head. I was missing a gasket. Oil was flowing along the engine until reaching the floor much further away...

To solve it, it was a matter of removing 3 bolts, put some liquid gasket and install back everything. Much easier than a trans to remove ;)

I would wipe the engine & check where oil come from, it should be easier to do on a Z than any other car with the room available around the L-engine.

Edited by Lazeum
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If it is indeed coming from between the engine and transmission, my experience is that sudden, large leaks are seldom the rear main seal. I'd think it is just as likely to be the input seal on the transmission. Is the oil level low in the engine?

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If it is indeed coming from between the engine and transmission, my experience is that sudden, large leaks are seldom the rear main seal. I'd think it is just as likely to be the input seal on the transmission. Is the oil level low in the engine?

Plus in most cases the manual transmission oil has a distinctive smell.

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Engine oil pan bolts tightish. No cracks in the pan? The sudden aspect of it coming on and enough to leave a trail..... Oil level should be down significantly I'd think.

I'd vote for the wash down and clean up and start by letting the car idle in the garage and watch how soon it starts and where it's coming from. If nothing after idling, then drive the car and park it and give everything a good once over.

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Ok it's not coming from clutch fork boot. Oil is definitely down. I filled it yesterday. I let it idle and I saw oil dripping from the plate that separates the engine and the tranny. So it has to be the rear main seal.

So my plan now is to drop the tranny, remove clutch, then the bearing is behind the clutch. Is that right?

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Ok it's not coming from clutch fork boot. Oil is definitely down. I filled it yesterday. I let it idle and I saw oil dripping from the plate that separates the engine and the tranny. So it has to be the rear main seal.

So my plan now is to drop the tranny, remove clutch, then the bearing is behind the clutch. Is that right?

Drop tranny, remove clutch, remove fly wheel....

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I had a leak before, it was located apparently from the same area as yours.

I've checked everything at the time and found it was coming from the window on the front of the engine on the head. I was missing a gasket. Oil was flowing along the engine until reaching the floor much further away...

To solve it, it was a matter of removing 3 bolts, put some liquid gasket and install back everything. Much easier than a trans to remove ;)

I would wipe the engine & check where oil come from, it should be easier to do on a Z than any other car with the room available around the L-engine.

Do you have picture of that leaking place? Sounds like i have same kind of symptoms..

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  • 3 weeks later...

Did you end up replacing the rear oil seal? Mine has had a slow leak for a while and I'm looking to change it out next week. Would love some advice if you wouldn't mind. A little intimidated by having to drop the tranny.

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I put in a new oil pan gasket and valve cover gasket. However, It turned out to be the rear main seal. I just put in a rear main seal stop leak 2-days ago, I havent seen any oil leakage since. I didnt think it would work, but so far it seems to be working. Give it an oil change first and then put in the stop leak. Dont over fill.

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  • 2 weeks later...

If the seal is really bad, it's just a quick temporary fix. If you're doing a ton of driving, I'd be careful. Nothing worse than being broke down on the 5 or the 405 at 6pm on a weekday. I picked up my ex who broke down on the 110S in Carson at 2am... it was still crazy.

Ask around for a FSM, some of these guys have them for your 240. I'll take a look as I have three but I think they are all 280Z, not sure the differences in removal procedure. Trans aren't too bad to pull either and the seal should be less than $15. If/when you change it, change the output shaft seal from the trans since you have to pull the driveline anyways. And don't forget to mark the DL too. Good luck man!!!

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my prior z did the same thing. Got home from work one day and followed an oil trail up the driveway to where my wife had parked the Z.

Cleaned it all up underneath and then ran it for a bit and oil was coming out the same spot between the transmission and engine. Took it in to a Z guy the next day and he just about glued the engine oil drain bolt in place thinking that was causing the drip (that was fun a couple months later when I went to change the oil). Eventually he decided it was the rear main seal and replaced it.

what brand of stop leak did you use?

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  • 1 month later...
Remove the transmission and take a peek.

Rear main seal can be changed with the engine in the car.

BUT: If it's a really big leak, what have you done recently to the car?

Normally the rear main seal doesn't leak that badly or just start suddenly.

Thanks for your information. I currently removing it. :D

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the tranny is easy to remove on this car because u have access to all the bell housing bolts. Just take out the main shaft, put a jack under the tranny, remove bellhousing bolts. Remove shift knob, take off cross member and slowly lower tranny. U may get a lot of fluid everywhere, so have some cat liter handy after ur done.

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