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1974 911: oil leak on the manifold

Hi all,
I own a 1974 911 with a 1975 911s engine. The engine was re-done a few years ago and there are 3 leaks remaining. One of which is super annoying since it leaks on the hot header and constantly smells. Yesterday I changed both gaskets on the two bottom valve covers and im somewhat confident that the job is well done. I went for a 30 min ride and put a cardboard underneath and went to sleep. This morning: 3 leaks however one of which is annoying: the passenger-side bottom valve cover drips a few drops on the manifold who (obviously) is hot and burns the oil... and smells. Now I changed the valve cover gasket, torqued it properly, etc.. I was wondering if the root of the leak was higher... I circled a (section Humide) on the 4th picture which seems to be very oily. any ideas? thanks!!




Old 10-06-2017, 06:58 AM
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I'm not familiar with the engine but is there a "triangle of death" on that engine like there is on the 3.2? If so I'd look up top side.
Old 10-06-2017, 07:14 AM
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That is no where near the triangle of death. Sources of leak vary but they can be a warped valve cover, to nylon nuts. For this, I suggest using a thin layer of RTV on the gasket. Don't go overboard.
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Old 10-06-2017, 07:35 AM
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Quote:
Originally Posted by cabmando View Post
I'm not familiar with the engine but is there a "triangle of death" on that engine like there is on the 3.2? If so I'd look up top side.
75s DO have the same setup of the oil breather, oil pressure switch and thermostat.

Quote:
Originally Posted by yelcab1 View Post
That is no where near the triangle of death. Sources of leak vary but they can be a warped valve cover, to nylon nuts. For this, I suggest using a thin layer of RTV on the gasket. Don't go overboard.
It's true it is no where near this area HOWEVER, oil can run out of this area, and it gets directed either down the side of the back engine tin, which would be right in the area he showed. The other pictures of the studs on the valve covers happen to be the lowest point so often oil will end up on those studs even if it originated from another area. Warped covers can cause this, but he has turbo covers and new gaskets. I'm not ruling out the valve cover gasket, but before gooping it up with RTV, i'd look for a few other suspect areas.

Firstly, check the drivers back of the engine bay tin, back by #3 cylinder. There's a plug there that can sometimes leak.



Secondly, there's an overflow pipe off the back of the CIS airbox that directs oil that get's puked into the airbox via the overflow hose coming off the oil tank and into the side of the airbox on a 75 CIS setup. Take off the airbox, and look if you have oil in there. look toward the back, you can see a little hole. Reach around the back side and feel that the hose is connected to this drain hole to a nipple that sticks out of the center of the back of the firewall.

If you recently changed out the valve cover gaskets, that means you drained and refilled the oil. If you slightly overfilled it, when you run the engine, oil will splash into the airbox and possibly make it's way down to this low point.

I mean yes, simple is always preferable, but just some more info to check for you.

Lastly, do you know if you have the oil restrictor upgrade on the cam feed lines? Just for my own research.
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Last edited by 75 911s; 10-06-2017 at 09:59 AM..
Old 10-06-2017, 07:51 AM
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That could possibly be a warped valve cover. It could also be from a leaking rocker arm. I would say, spray the entire area with brake parts cleaner, and get ALL of the residual oil off. Start the car, and let it run for a good 30 minutes or so, then shut off. Let sit over night, and come back. Hopefully it will be easier to pinpoint exactly where the oil leaks are coming from.
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Old 10-06-2017, 07:53 AM
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Gents, thankd for all your replies and ideas.

Duane, the potential leaks on your picture makes sense and in my engine, the other side of the tin (circled on your picture) is exactly where i noted that the section is humid: above the valve cover.

I'm usually super methodical but when it comes to my car, everything seems to be blurry ...ok so my plan of action is to follow turbobrat930's suggestion and clean the around the calve cover with break cleaner, go for a ride and then let it rest. By doing so, im hoping to either confirm the valve cover as leaking or confirm that the leaks comes from higher.

will keep you posted!
Old 10-06-2017, 08:30 AM
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I hope you find your leak without too much work or money involved. I found my two spots up top that made me think my VCs were leaking as well my my oil cooler. Turned out to be from the triangle. I didn't figure it out until I dropped the engine for some other work I needed to do and saw the oil trail from top to bottom.

Good luck!
Old 10-06-2017, 09:18 AM
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1974-911 are you in europa..? those valve cover gasket look axactly like one euro supplier have and they are very very bad.I did a service on friend of mine 911, silly me I used his gasket he has bought. Exactly the same leaks you are having.
Or...

The oil could be from couple of places.as mentioned above.1st did you or somebody do a 1000 miles check up on the engine after it was rebuild?
If not it is possible you rocker arm shaft are loose.
The other oil leak looks like from the camshaft oil line fitting to the engine .You can have the trought bolt tight but the leak is here.


If you rocker arm shaft have move ,they will leak they are supposed to be be here





Ivan
Old 10-06-2017, 09:29 AM
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couldn't wait to tomorrow, I went down to the garage while on a conf call and snapped a few pictures. the ToD (trangle of death) area looks clean. a little dirty/oily but doesn't seem like it has been leaking... what do I know?! I think the determining factor will be cleaning the top AND bottom par, take pictures, and go for a 30 min ride ...and take the same pictures.


Old 10-06-2017, 10:10 AM
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Quote:
Originally Posted by proporsche View Post
1974-911 are you in europa..? those valve cover gasket look axactly like one euro supplier have and they are very very bad.I did a service on friend of mine 911, silly me I used his gasket he has bought. Exactly the same leaks you are having.
Or...

The oil could be from couple of places.as mentioned above.1st did you or somebody do a 1000 miles check up on the engine after it was rebuild?
If not it is possible you rocker arm shaft are loose.
The other oil leak looks like from the camshaft oil line fitting to the engine .You can have the trought bolt tight but the leak is here.


If you rocker arm shaft have move ,they will leak they are supposed to be be here



.




Ivan
This^^^^^^ Rocker arm shaft especially since the engine was overhauled. They're either not tight enough (21' lbs) or positioned wrong. Many rebuilders don't tighten them to the correct torque then they walk out of the bores.
Old 10-06-2017, 10:18 AM
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will look at the rocker arm shaft

btw, im not in europe, im in Montreal, Canada, the car us a US model and (i was told) that the valve covers were replaced with the turbo model.
Old 10-06-2017, 11:07 AM
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Hi Canadian..i just wondered because the French language in the pics...
Ok let us know what you `ll find..
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Old 10-06-2017, 11:15 AM
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yeah, I was sharing the pics with a friend, doing some forensics

ok so I went through the entire internet 3 times this afternoon and it would make sense to explore the rocker shafts for leaks: tighten them and install RSR seals. these are the 2 videos that better explain the rocker shaft leaks for noobs like me.

https://www.youtube.com/watch?v=G7cOSqKN-0A
https://www.youtube.com/watch?v=Fm7S4yQL7xk -- ffwd to 6:05 sec (leaks on the floor)

Now anyone knows or can share a link on how to get to the passenger side rocker shafts? i imagine I have to remove the cover where the chain tensionner is?
Old 10-06-2017, 01:39 PM
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Quote:
Originally Posted by 1974-911 View Post
yeah, I was sharing the pics with a friend, doing some forensics

ok so I went through the entire internet 3 times this afternoon and it would make sense to explore the rocker shafts for leaks: tighten them and install RSR seals. these are the 2 videos that better explain the rocker shaft leaks for noobs like me.

https://www.youtube.com/watch?v=G7cOSqKN-0A
https://www.youtube.com/watch?v=Fm7S4yQL7xk -- ffwd to 6:05 sec (leaks on the floor)

Now anyone knows or can share a link on how to get to the passenger side rocker shafts? i imagine I have to remove the cover where the chain tensionner is?
Don't need the seals just center and tighten.
Old 10-06-2017, 03:54 PM
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Quote:
Originally Posted by 1974-911 View Post
yeah, I was sharing the pics with a friend, doing some forensics

ok so I went through the entire internet 3 times this afternoon and it would make sense to explore the rocker shafts for leaks: tighten them and install RSR seals. these are the 2 videos that better explain the rocker shaft leaks for noobs like me.

https://www.youtube.com/watch?v=G7cOSqKN-0A
https://www.youtube.com/watch?v=Fm7S4yQL7xk -- ffwd to 6:05 sec (leaks on the floor)

Now anyone knows or can share a link on how to get to the passenger side rocker shafts? i imagine I have to remove the cover where the chain tensionner is?
I did the RSR seals on my 3.2 when I put it back together. My personal take is they're a waste of time as it's difficult to install them even with some lube without ending up pealing them a bit when they go in. Not sure I'd do it again. As long as you install the shafts properly and torque them ( I think John Walker recommends going a bit tighter than the torque spec but you'd want to verify by searching) I think you'd be fine.
Old 10-06-2017, 04:54 PM
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Originally Posted by cabmando View Post
I did the RSR seals on my 3.2 when I put it back together. My personal take is they're a waste of time as it's difficult to install them even with some lube without ending up pealing them a bit when they go in. Not sure I'd do it again. As long as you install the shafts properly and torque them ( I think John Walker recommends going a bit tighter than the torque spec but you'd want to verify by searching) I think you'd be fine.
Agree 100% waste of time just make sure to torque to 21 foot lbs. The manual has a different torque spec. A guy who builds race engines taught me this.
Old 10-07-2017, 03:52 AM
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Good morning gents, quick q: what's is the easiest way to access the the cyl no4 rocker shaft? cyl no4 is the first one on the right when looking at the engine. the one I need to access is for the intake valve as I suspect it leaking oil.

I mean I know and understand that the right way to do this is engine out but is there another way?

1) through Chain Box Tensioner Cover?
2) through the valve cover?

thank you!

Last edited by 1974-911; 10-10-2017 at 03:39 AM.. Reason: typos
Old 10-10-2017, 03:36 AM
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Originally Posted by 1974-911 View Post
I mean I know and understand that the right way to do this is engine out but is there another way?
honestly: no
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Old 10-10-2017, 04:19 AM
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Hi..it is not hard..remove the spark plugs wires.Then remove the valve cover and look inside by using a mirror.Look at the rocker shafts for wetness.You can put on allen wrench to see if they are tight.But before that look if they are in the right place.The pin should be slightly showing on the smaller bang.
Like on this picture all pins have to bee to the thinner side....
Old 10-10-2017, 04:50 AM
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Flojo..you seem to have the same leak on the rocker pins...right?
Ivan
Old 10-10-2017, 04:55 AM
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