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lmaoufle Samba Member
Joined: June 02, 2015 Posts: 63 Location: France
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Posted: Tue Jun 10, 2025 5:40 am Post subject: The mysterious oil leak |
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Hi all!
I have been fighting an oil leak for a long time, my engine was brand new 2 years ago, then started leaking from the flywheel 6 months later
So I did remove the engine, but as I had only half day to fix it and go home, I went for the quickest solution and change the main rear seal. And guess what the leak was still there
So now 1 year later, my gearbox died and so engine has to come out and here we are fighting once the again this leak.
So here are the pics
I really don't now where the leak is, there is some oil from the main seal but also on the camshat plug, and the oil gallery plug is also dirty, so difficult to know.
And what I really don't understand is the gearbox! it is convered with oil!!! it doesnt smell and looks like engine oil
So any ideas to explain all of that? worst case, I change rear seal, oil gallery plug, camshaft plug, but I am not that confident to mess with this important stuff  |
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SGKent  Samba Member

Joined: October 30, 2007 Posts: 42400 Location: at the beach
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Posted: Tue Jun 10, 2025 7:28 am Post subject: Re: The mysterious oil leak |
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There are many places oil can leak on these. The one that bit me the worst on a type one engine was my 1971 had so many miles on it that the shims cut a groove that went all the way down to the dowel pins so oil would leak from them. The quick fix was to put sealer in the dowel pins. The permanent fix was to replace the crankshaft. I have also had gallery plugs leak even with a good sealer on the threads. Best solution is to clean it well, put a fluorescein dye in the oil, run it 20 minutes and see where the oil is coming from using a black UV light, _________________ "Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin |
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Glenn  Mr. 010

Joined: December 25, 2001 Posts: 79428 Location: Sneaking up behind you
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Posted: Tue Jun 10, 2025 8:31 am Post subject: Re: The mysterious oil leak |
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First I only use the red flywheel seals.
You can easily remove the pipe plug and reinstall with some loktite thread sealant.
The cam plug doesn't look like the stock metal one. So the only solution is to remove it and use the plastic Mexican plug. _________________ Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"
Member #1009
#BlueSquare
עַם יִשְׂרָאֵל חַי |
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timvw7476 Samba Member
Joined: June 03, 2013 Posts: 2479 Location: seattle
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Posted: Tue Jun 10, 2025 5:39 pm Post subject: Re: The mysterious oil leak |
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Great images.
But the one that helps most is backside of flywheel.
Any radial streaks coming off the main seal/main bearing area?
If not you can concentrate on the cam plug area. Looks like a cc of oil is right there. |
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Mispeld Samba Member

Joined: April 29, 2018 Posts: 364 Location: Jacksonville - Coastal NC
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Posted: Tue Jun 10, 2025 6:20 pm Post subject: Re: The mysterious oil leak |
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Just curious, how did it look externally around the starter area? I've been dealing with an oil leak that I can't figure out that looks like yours being covered inside the bell housing. Oil seemed to be leaking out of the starter opening and bolts. I've changed the rear main seal twice, and I didn't see any signs of anything leaking once I pulled the engine and flywheel. You can see my old pictures in my gallery on pg 2 to compare. I hope you can figure it out! _________________ Tom
1977 Westy. 2.0 Fuel Injected. |
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lmaoufle Samba Member
Joined: June 02, 2015 Posts: 63 Location: France
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Posted: Wed Jun 11, 2025 12:39 am Post subject: Re: The mysterious oil leak |
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Thanks all for your comment, but I still don't understand:
- if it is the cam plug, oil should go down to the case? so why is the case dirty from the cam plug to the rear main seal?
- why the gearbox is covered with oil? and not the engine case?
I will take picture of the flywheel and clutch plate but I really thing they are clean as new.
and for @Mispeld yes the starter area is covered with oil, the other of the gearbox is covered also, even the rear top engine case!
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timvw7476 Samba Member
Joined: June 03, 2013 Posts: 2479 Location: seattle
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Posted: Wed Jun 11, 2025 2:38 pm Post subject: Re: The mysterious oil leak |
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Good Question(s).
The spinning flywheel assembly can help throw oils all around the clutch housing. Also there is the gearbox seal right next to it & yeah it weeps gear oil adding to the mystery. But gear oil has a sulphur stench that follows it. I'd pick up some of that material on the transaxle & sniff it. Time to swap the input shaft seal as well. |
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SGKent  Samba Member

Joined: October 30, 2007 Posts: 42400 Location: at the beach
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Posted: Wed Jun 11, 2025 4:04 pm Post subject: Re: The mysterious oil leak |
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Many flywheels have a rubber o-ring that goes in a groove on the inside of the flywheel where it mates to the crankshaft. It keeps oil from leaking from thru the border between the crankshaft and flywheel. Make sure it is there and not cracked, hardened, or broken. If it is missing or damaged that may be your leak. But if it is there and in good condition, grab this pin with the arrow with a set of vise grips and pull it out, trying not to damage or deform it. Look inside the pin hole and see if it is wet with oil. If it is, look on the outside side of the pin hole to see if it shows a slice thru where the shims may have cut thru to the pin. If not, you still should not have that much oil between the crank and flywheel as in your photo.
_________________ "Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin |
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Abscate  Samba Member
Joined: October 05, 2014 Posts: 23784 Location: NYC/Upstate/ROW
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Posted: Thu Jun 12, 2025 2:01 am Post subject: Re: The mysterious oil leak |
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Remember, it’s not a leak until you are catching enough in a pan to pour back into the motor inthe morning. Anything less than that is just a pizza box lubricator _________________ 🇺🇸 🇺🇸 🇺🇸 🇺🇸 🇺🇸 🇺🇸 🇺🇸 🍊 🍊 🍊 |
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