PCA SDR

In the first serious trial of my 911 SC "project car" at Fontana last week, I developed an oil leak that got me black flagged. I can't tell exactly where it's coming from; the oil is clean and it's harder to trace. With car on lift, it looks like one of these: left side lower valve cover gasket, left rear chain cover gasket, or a left side oil return tube (head to crankcase). It is a very slow leak around town (and on the way back from Fontana), a drop every day or so, and thus hard to pinpoint. It must have leaked more at sustained hi rpm and blown around at hi speed. I had just changed from 10-40 to 20-50 oil before the event, and after this I noticed the oil pressure was a little higher when the engine was cold.

Which of these areas (valve cover, chain cover, or return tube) sees the most increase in oil pressure at hi rpm?

Could left side leaks be worse due to the repeated right turns on the Fontana course?

To change valve cover gaskets, do I have to drain oil first? These gaskets were fresh from a valve adjustment when the engine was out, but I did not change the nuts or washers (Pelican recommends this). Can it leak around the nuts themselves if you don't change them?

Thanks for any and all wisdom.

Actually I did change the nuts and washers. Forgot, but I see they are new.

Dave:

Your initial ideas are good ones. Valve covers, cam housing seals, chain covers ... all good guesses. Did you change to a synthetic oil type? Synthetic blend? Synthetics have a way of cheating past old seals.

A couple of seals that can develop leaks in these "older" 911's are under the intake system: the O-ring on the temp sensor (I think that's what it is), and/or the seal on the breather tube plate, or the thermostat on top. My 3.0L engine developed leaks there and trickled down onto the left side. I searched for a while in vain before Kinninger finally found 'em.

Fontana is a lot of right turns, thus the potential for left side migration of fluids from the top of the case.

Take a small LED flashlight and small hand-held mirror and look all around/under the intake manifold right in the middle of the top of the engine. If it looks wet at all ... bingo.

Hope that helps.

Dave Diamond wrote: I can't tell exactly where it's coming from; the oil is clean and it's harder to trace.

You might consider using a UV fluorescent leak detection dye in the oil and a blacklight while on the lift to pinpoint the leak source. This is what Steve G. has always done when my cars have oil leaks. It is easier to differentiate the old oil from the newly leaked oil when it glows under a UV light source. The way clean oil gets spread around on an engine from wind and G-forces while driving makes it very difficult to determine where it originally came from. As Dan said, it may very well be coming from the top of the engine.

TT

[quote][/quote]
I used Brad Penn 20W-50, partial synthetic.

I'm reasonably sure the leak is not from the top, but I will check again. I wiped off the bottom after the leaks, but around town, even revving it up, the leak is slow enough that it's hard to see much. The engine is pretty clean bottom and top, and the new oil is clear. I'll drive it harder for longer and see if I can re-create more evidence. Is it bad to rev it high for long while stationary in the garage? That would avoid the wind problem.

Fluorescent dye -- great idea -- sounds like something from CSI. Maybe Steve G. has another life...?

Secret identity for sure...
The ultraviolet oil dye is the way to go.
I have done this for about a dozen drivers on this board when they couldn’t find the leak themselves after multiple attempts. The entire process is about $120 and comes with a cool digital picture of the findings so the owner can do his own DIY repair. The cost is far less than the tools needed to run the test.
If that doesn't find it there is a similar test using compressed smoke to find oil leaks that occur with excessive case pressure like during extended periods of full throttle.

Pretty cool stuff…

Steve Grosekemper wrote:Secret identity for sure...
The ultraviolet oil dye is the way to go.
I have done this for about a dozen drivers on this board when they couldn’t find the leak themselves after multiple attempts. The entire process is about $120 and comes with a cool digital picture of the findings so the owner can do his own DIY repair. The cost is far less than the tools needed to run the test.
If that doesn't find it there is a similar test using compressed smoke to find oil leaks that occur with excessive case pressure like during extended periods of full throttle.

Pretty cool stuff…

+1. Do the dye test. Totally worth it.