Oil leak - seems like cylinder base gasket is blow

[totle]

Just had a trip to Germany and Nürburging. Noticed that engine was leaking oil, but was not able to do anything until I got back home.
Engine was never over revved.

Was under the engine today, and it looks like the cylinder base gasket on cylinder #4 is pooped out.
I'm really not sure, but looks like the gasket on this cylinder is more out than on the other cylnders, and the leak looks like coming from this place.

Not any leak when engine is not running, but when running it leaks too much for me to like driving it.

I had a misfire due to coil problem earlier, could this have caused too much pressure in the engine to blow this gasket?

Any suggestions why this has happened?
Engine is newly rebuilt, new head studs and torqued according to spec.

Seems like I have to take out the engine again to verify and fix

[Flat6pac]

The gasket is a metal gasket and isnt under any pressure from compression or turbo boost, simply ambiant pressure inside the engine which is handled by fumes inside the oil tank being sucked into the air flow sensor then burned.
Need to check the head studs for torque.
Bruce

[totle]

Thanks Bruce, will have a look at the torque.
I used new head studs from competitive engineering, and torqued according to spec.

Yesterday I cleaned the engine and started the engine for a minute, and it started to drip right away.



This is the gasket that I have been using. Looks like they are sort of teflon on, but might be copper underneath.

[Walt Fricke]

Trond

You can retorque your head stud nuts with the engine still in the car. Consider it as part of your first oil change. I'd for sure do that right away. Torque them all for good measure.

I'd do that because the alternative is not attractive:

If you have a piece of that sealing ring actually sticking out, you have a big problem. Somehow it got damaged in assembly?

You can pull just the cam stuff on that side, and just that one cylinder, in order to replace it if somehow it was misaligned and was damaged in installation.

Hope a fix is easier than this.

Walt

[totle]

The engine bay is so tight, so I think the best way is to drop the engine.
In case the retorque does not work for me I still have to drop engine to look at the cylinder.

My plan is as you described. Will only need to take apart right cam tower, and change base gasket on cyl #4.
Then re-torque all head studs and re-adjust valve clearance.
While rebuild, I changed valve guides on exhaust side, and had the seats grinded, so guess the exhaust side needs to be re-set

[cstreit]

Can you try and better lit picture of that area? Hard to tell what's going on there, but that area really isn't under much pressure per se. I wonder if you have a loose or broken head-stud causing it to loosen up. Can't imagine what would "push" the gasket out.

How many miles are on this engine?

[totle]

Will try to see if I can get a better picture tomorrow.

The engine is just recently rebuild 4 weeks ago.
Might be that I have bent the gasket in the assembly process.

The head studs are new from competition engineering in the rebuild

[totle]

I have tried to take a better picture.

[john walker's workshop]

may be a case through-bolt o-ring. were they replaced recently? undisturbed originals don't tend to be leaky, but fresh blue ones maybe. does the copper gasket seem to be protruding outward?

[Walt Fricke]

Does this new, better, picture show the protruding base gasket? Just to the left of the black cylinder tin? Nothing should be sticking out there.

Though it is a little difficult to see how this could happen, because the lower part of the cylinder forces the copper gasket to stay round, so there isn't anything to protrude unless somehow the malleable copper is crushed to make it thinner but wider.

I wonder if the fact that it only leaks with the engine running helps differentiate things. There is usually a fair amount of positive pressure in the engine case - more than one might expect - in our older 911s. I think that is mainly what would make it leak at the cylinder base if the seal is bad.

But case through bolts would only leak as you show when there is oil pressure in the engine from the oil pump.

On the other hand, I don't think this lower case bolt is connected to the oil pressure system. The oil gallery is on the top of the engine, and the main bearings are oiled directly from it. The piston squirters get oil from the upper through bolts. I don't think there is a connection to that particular lower bolt. If that is correct, I think it would make it less likely that you'd have a leak there.

I've worried about creasing or crushing these as I installed the cylinder - paid attention to getting them to stay in place as the cylinder starts into the spigot, and keeping their cutouts for the studs where they should be after removing the ring compressor.

You might clean all the oil off, spray some brake cleaner up in there, and clean again. Then run the engine to see if there is oil again right up against the cylinder gasket. If this is a bolt seal issue, I doubt oil is spraying out, and the air blowing down ought to keep what seeps out from migrating up to the cylinder base. Maybe.

In some ways, the worst outcome is for you do do a partial disassembly, and not find any likely cause. Now's the time (if the engine is still in the car) to try to pin the origin down a little better, if possible.

Walt

[totle]

My rebuild was more a top-end rebuild. The engine case was not opened, so the through-bolts was never touched. That means they have the old o-rings.

To me it looks like the base gasket on this cylinder is more protruding than on the other cylinders.

The engine is still in the car. Does not have the time to drop it yet. To many other projects going on.
Good tip about the brake-cleaner. Will clean properly later today and see if I can figure out where the leak is coming from.
Very tight under there and the cylinder tin is in the way of viewing

[Walt Fricke]

Trond

Another thing you can do is pull the right side engine cover sheet metal. The piece that sits above the right side cam oil line. That will allow you to look (some) at the top of the #4 cylinder, which conveniently is closest. Not that I'd expect to see oil there, but it is easy to do and won't take the kind of time you will need when you pull the engine.

One advantage of the collapsible oil return tubes is you can get them out of the way. Then you might be able to remove the cylinder tin retaining clip up top and pull that piece of tin for a better look.

Though prospects for a fix short of pulling a cylinder off are starting to look gloomy.

Let's see - if you loosened all the head stud nuts on that side, and applied a wicking sealant (Loctite wicking threadlocker?) liberally from top and bottom of the cylinder base, then retorqued? Anyone give odds on whether that would solve a copper gasket damage issue?

Walt (a guy has to keep thinking)

[totle]

Well guys, then I finally had the time to drop the engine and inspect further, and it was as I expected.
The base gasket has been sliding and caused the leak. How this has happend I have no clue of.
Maybe I did a lousy job when mounting.

Here is a picture of what the base gasket looked like, and you would see why the oil leak

[Walt Fricke]

Hmmm

But the gasket should look nicely coppery all around. Like what one can see in the picture of its neighbor.

Yours is distorted, displaced, and perhaps thinned at the bottom, to be sure. But why is the left side all darkened, as far as the photo shows?

There should not be any side loading trying to force the gasket out.

Could the gasket itself have been deficient from the start?

Is it possible that the case spigot surface is not true? Or that the cylinder base is not true?

[Steve@Rennsport]

Some thoughts,....

Boost pressure at 1 bar? Is the waste gate working properly to prevent overboost?

Stock HE's or a header system?

What head studs did you use?

[Ken911]

Originally Posted by Walt Fricke

Hmmm

But the gasket should look nicely coppery all around. Like what one can see in the picture of its neighbor.

Yours is distorted, displaced, and perhaps thinned at the bottom, to be sure. But why is the left side all darkened, as far as the photo shows?

There should not be any side loading trying to force the gasket out.

Could the gasket itself have been deficient from the start?

Is it possible that the case spigot surface is not true? Or that the cylinder base is not true?

it's dark because that is a teflon coated copper gasket. I have done a couple rebuilds the ones i got were all like that.

[totle]

Originally Posted by Steve@Rennsport

Some thoughts,....

Boost pressure at 1 bar? Is the waste gate working properly to prevent overboost?

Stock HE's or a header system?

What head studs did you use?

Waste gate has been inspected and I have found no issues

I'm running OBX headers and Brian's (RarlyL8) dual out free float muffler

Heads studs from Walt at Competition Engineering

[Steve@Rennsport]

I have no experience with OBX headers, however I've had plenty of boost creep issues with B&B & GHL headers. If the OBX's use the same size wastegate plumbing, I'd confirm boost levels with a standalone gauge to make certain its no more than 1 bar.

FWIW, the ONLY head stud we will use on Turbo engines are the factory 993TT ones. This is due to problems with loose heads using aftermarket ones.

JMHO, of course.

[Eagledriver]

Perhaps the teflon coating on the gasket allowed it to "creep" out of position. Might want to find some without the teflon coating.

-Andy