Oil Leak - Help

[tom1394racing]

I am trying to fix a small persistent oil leak on my 3.0 RSR spec motor. The case is a '79 SC Al case. I have traced the leak to the junction between the cooler and the case as shown below.



I removed the cooler and pressure tested it to find no leakage. The case surface did show some sign of leakage but the source was not apparent. The fresh oil in the pic is drippage from the case to cooler seals that occurred after the cooler was removed. The area behind the through bolt washers was clean, dry and sealed with RTV.



I replaced the (3) case to cooler sealing rings and reinstalled the cooler only to find the same leakage.

I recently read a thread here regarding case porosity in this region and the need to seal it with some type of sealant. Can anyone expand on this and possibly explain where to seal and what type of sealant to use?

[Lapkritis]

There is a service bulletin for the 7 o'clock indent in the cavity behind the cooler on the case to be epoxied. Looks like yours is yet to be done.

Edit: JB weld or similar with a thorough cleaning should do the trick.

[pete3799]

Looks like an O ring leak......maybe try the green Viton O rings.

[304065]

Tom, there is also some recent info that the replacement cooler seals don't have the same dimensions as the originals, causing a leak. I supposed you used Charlie's? After my RMS fiasco(s) I won't touch anything made by Reinz. Anyway, I would get a handful of seals from different suppliers and mic them up. Also depth mic the case recess and the cooler.

[carrerarsr65]

it seems that the jb should do it for you , aggod cleaning first with some brake clean spray to degrease,also make sure your work area is at least 50 degrees s it sets up right, good luck al

[JJ 911SC]

Originally Posted by 304065

Tom, there is also some recent info that the replacement cooler seals don't have the same dimensions as the originals, causing a leak...

Check the chart I did @ post #8 of Oil Cooler Seals Leekage with the Engine on the Wall

[tom1394racing]

Thanks for all the input.

Interestingly, the area identified in the service bulletin looked pretty dry when I removed the cooler. Also I am using the red seals, procured from a local, very experienced Porsche engine builder.

I think I will remove the cooler, clean up the cavity, apply the JB weld per the service bulletin and use some Curil-T on the seals.

[brighton911]

Tom, on mine, the oil leak was quite obvious as coming from the known casting issue. I wonder if the leak is from one of the case through bolt O rings, (at the acorn nuts)?

Dave

[tom1394racing]

The acorn nuts and beveled washers were completely dry when I removed them to check.

[brighton911]

Well Tom, that's good that they were dry, eliminates that possibility. Seems to be pointing more strongly to the seals, good luck and post the final solution.

[cmcfaul]

For the longest time my car had a mystery oil leak in that region. Only recently discovered if I keep the oil level in the middle of the gage when hot (not toward the top) the crank case breather hose would not weep and cause oil to run down the oil cooler and the back of the engine.

If all else fails run half a qt less oil than usual and see what hopefully does not happen.

Chris
73 911 E

[Lapkritis]

I can see the hole in his second picture. Look at the indent - you can see the edge of the break.

[boyt911sc]

Tom,

Could you pressure test the engine oil cooler and do the immersion test before coating it? Just curious if you could detect the microscopic crack/s with a pressure test.

Tony

[tom1394racing]

Tony

I pressure tested the cooler and found no leaks. I JB welded the indent in the case and used Curil-T on the cooler seals. Have not tried it out yet.