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Oil Leaking from where??

Just going through that most frustrating of situations where I have completed a top end rebuild of my '86 930 at a local porsche guy (valve guides, valves and piston rings) along with replacing most hoses and seals and I have multiple oil leaks still! I also have a nice little puff of blue smoke on start-up that I didn't have before...(reason for rebuild was double digit leakdown results in 3 cylinders and multiple oil leaks) so I'm trying to work with my guy's explanation of what to do;

1. The piston rings will take a while to seat so expect a little smoke on start-up.
2. Put some miles on the car before worrying about the oil leaks. I am relatively new to porsches but not german cars and this sounds somewhat contrary to logic.....

Can anyone give me some thoughts on the above?

I am also curious what others would do as we decided not to split the case despite a small leak from the #8 bearing and tried some wonder mercedes? glue and oil is seeping through the glue - has anyone tried this with any success before? I of course now realize that I should have bitten the bullet and split the case.....just adding to my frustration of course!

Thanks in advance for any advice.

Rob

Old 05-04-2012, 03:58 PM
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Sounds like a lot of bs to me.
I think you need an extra set of eyes on it, second opinion as it were.
Old 05-04-2012, 05:20 PM
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Rob, I sort of went thru something similar when I had my recent bottom-up build. It was done by one of the best, and he urged me to not obsess about some minor leaks (actually weeps).

I did find that replacing the thermostat cover gasket and sender o-ring seemed to reduce the mystery leaks. One big fix was routing the breather hose (mine used filter at the end) outside the car - prior oil mist and fumes were leaking out the filter onto the top of the motor and finding its way along the bottom. At one pt - I was convinced it was leaking from the cylinder/case interface -not the case (no pun intended).

Still a minor weep coming from rear main seal and mine too has small puff of smoke on start-up. After that - not a bit of smoke even at high boost. Just did check-up leak down and numbers were perfect.

Nevertheless, if something sounds "unreasonable" it might be - even the best can cut corners on these fickle engines.

Best,
Frank
Old 05-04-2012, 06:02 PM
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So I took the car to someone who has a lot of positive feedback on this site (Mark at Redline in the LBC) who was great (took the time to explain and show what he was talking about, knowledgeable, etc, etc...excellent resource) and the good/bad is that much of what I had been told was correct; the question I had but didn't ask at the time is when you have new piston rings; how long should the seating process take?

Rob
Old 05-21-2012, 03:31 PM
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It is hard to say precisely how long it takes for the rings to seat, but it happens fairly quickly on boosted engines as the boost pressure helps with the process . . .
Old 05-21-2012, 04:08 PM
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I would tend to disagree with ronnie a little... Here is why. When you rebuild a turbo motor you are supposed to stay off boost for first 500-1000 miles (some advice will differ I'm sure) and the engine is typically a lower compression motor (like 7 to 8:1) which means there is not a lot of compression or force to help seat the rings.

With all of that being said, when I rebuilt my 930 I have no idea how long it took to seat the rings but I never had smoke.... so, may be rings, may be something else.

On a rebuild such as yours did you have the cylinders cross hatched again for new rings? Did you re-do the cylinders or just replace the valve guides, seals and rings or did he do any machining? Did he check tolerances on rocker arm shafts and inspect for cracks? Lastly, rocker-arm shafts can be at very high risk to leak after removal and re-install if no attention was paid to their condition? Did he re-finish the rocker arms themselves or look at the cams?

Just making sure you did a top end job and what you expected to get based on what you paid for.... just trying to help. Please take this as merely advice or my .02 on where I would look and possible causes to your issues.

One last thing, are you leaking behind the cam box cover where the chains and tensioners are held? This is the surface between the chain box and cam tower where the cam go's into the cam tower... also a possible spot to leak.

Best of luck in your search for the culprit.

Cheers,
Bryan
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Old 05-21-2012, 05:04 PM
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I have had friendly debates with others regarding "staying off boost" with a new build, and like you said, there are many opinions on this. I follow the advice of two vastly experienced engine builders I know personally - three heat cycles at a stand still and then let it rip from that point on!
Old 05-21-2012, 07:13 PM
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i was a the P dealer a few months ago and they started up a brand new turbo 911 a puff of smoke. the service tech i was dealing with sort of chucked and said see even the new ones do it.
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Old 05-21-2012, 09:29 PM
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Thanks guys, good info; it does seem like every car behaves a little differently and I probably need to try and figure out that fine line between reasonable concern and just enjoying the many great things about the car.

Cheers,

Rob

Old 05-22-2012, 11:32 AM
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