Cylinder scoring

[PSManring]

Went to the track and ended up with a coat of oil over the engine. I took it to a reputable race shop where they performed some testing. "Oil leaking after track event. Oil pooling under intake . Perform leak down and compression tests. 15% leakage on cylinder #2, scoring on bank one cylinder walls."
So my question is what can I do to fix this? I do not want to scrap the engine as I can daily drive it with out blowing oil everywhere. Can I do new pistons on that bank of cylinders with new or used cylinder (heads?/Jugs? I don't know the proper term)?
I would love some input. Thanks for your help.

[Glenfield]

Be careful PSManring.

I had a mechanic perform a leak down and compression test which returned similar results on cylinder #5. He borescoped the cylinder and diagnosed cylinder scoring. Tore engine down and cylinder #5 was perfect. Compression/leakdowns return false negatives and borescopes invite user error. Even at the most respected shops.

You have different symptoms and do appear to be more consistent and uniform. Also unlikely to have any carbon buildup skewing numbers. Just my 2 million cents though.

[ClickClickBoom]

Originally Posted by Glenfield

Be careful PSManring.

I had a mechanic perform a leak down and compression test which returned similar results on cylinder #5. He borescoped the cylinder and diagnosed cylinder scoring. Tore engine down and cylinder #5 was perfect. Compression/leakdowns return false negatives and borescopes invite user error. Even at the most respected shops.

You have different symptoms and do appear to be more consistent and uniform. Also unlikely to have any carbon buildup skewing numbers. Just my 2 million cents though.

Differential Compression tests are primarily a diagnostic trend monitoring device. “Pooling under intake” tends to indicate a oil leak in the oil venting system. Beware, second opinion before tearing engine down.

[JSV798]

Perhaps you just overfilled with oil and extra heat of track event caused oil to expand, leading to spillage. I never fill higher than halfway between marks on dipstick, checked with engine warm and idling.

[MBAtarga]

What engine are we talking about 3.0, 3.2, 2.7 ?

[Jeff Alton]

^^^^^ This, what engine is this? Is it stock or modified in any way??

[Trackrash]

Let me see if I got this correct. The engine blew out some oil, and the mechanic did a compression, leakdown, and borescope? Not sure how those tests would find the source of the oil leak.

Did he check the oil level or the tank vent setup?

Leak down means little with out knowing where the air is leaking. Scoring on bank one? What does that even mean? I could be wrong, but it sounds to me like this mechanic is looking for work.

[ClickClickBoom]

Originally Posted by JSV798

Perhaps you just overfilled with oil and extra heat of track event caused oil to expand, leading to spillage. I never fill higher than halfway between marks on dipstick, checked with engine warm and idling.

Volume of oil at different temps is the same until it becomes gaseous.

[Arne2]

Originally Posted by ClickClickBoom

Volume of oil at different temps is the same until it becomes gaseous.

Not so sure about that. Both of my Porsches ('84 3.2 and '72 2.4) show low on both tank gauge and dipstick until fully up to temp. Easily a full quart difference from cold to full warm. So there's some expansion going on in there.

[ClickClickBoom]

Originally Posted by Arne2

Not so sure about that. Both of my Porsches ('84 3.2 and '72 2.4) show low on both tank gauge and dipstick until fully up to temp. Easily a full quart difference from cold to full warm. So there's some expansion going on in there.

Do not mistake anecdotal experiences with science. When the 911 is “cold” the oil has more viscosity and tends to adhere to every surface inside the engine in a thicker film. Once the engine heats the oil, the viscosity reduces, allowing the ‘gravity return” of the oil to the sump and then the tank.

Plug in whatever numbers you prefer:

https://my.hostmysite.com/ssl/30/thermotab.net/infoPages/Table_limits.html

[stownsen914]

Excessive blowby can result in excessive oil mist coming out the breather and result in coating the engine with oil, but there are many other possible causes. I'd want to give the engine a good cleaning and then reproduce the leak to trace the source before making any decisions how to proceed.

[Trackrash]

Originally Posted by stownsen914

Excessive blowby can result in excessive oil mist coming out the breather and result in coating the engine with oil, but there are many other possible causes. I'd want to give the engine a good cleaning and then reproduce the leak to trace the source before making any decisions how to proceed.

Yes.

I have had a motor that had broken piston rings in one cylinder, so basically no compression. The symptom was LOTS of smoke coming out of the breather. Enough that I could see it in my mirrors while driving at night. Still there was not any noticeable liquid oil blowing out. (this was not a 911 btw)

Is that what the mechanic was thinking was wrong with your motor?

Maybe you could share the numbers from the compression and leakdown tests?

[stownsen914]

Sometimes excessive blowby can result in the extra oil overwhelming whatever it is that catches is. For most stock 911s, I believe this would be the airbox, which can start to fill up and/or leak. And then the mess ensues.

Or it could be as simple as a leaky breather hose. Tracing the source of the leak will reveal a lot.

[brshap]

Originally Posted by ClickClickBoom

Do not mistake anecdotal experiences with science. When the 911 is “cold” the oil has more viscosity and tends to adhere to every surface inside the engine in a thicker film. Once the engine heats the oil, the viscosity reduces, allowing the ‘gravity return” of the oil to the sump and then the tank.

Plug in whatever numbers you prefer:

https://my.hostmysite.com/ssl/30/thermotab.net/infoPages/Table_limits.html

I'm not sure I agree. The specific volume of liquids generally increases as temperature increases and I don't think engine oil is any different.

https://www.engineeringtoolbox.com/temperature-density-petroleum-lubricating-oil-lubricant-volume-correction-ASTM-D1250-d_1943.html

[ClickClickBoom]

Originally Posted by brshap

I'm not sure I agree. The specific volume of liquids generally increases as temperature increases and I don't think engine oil is any different.

https://www.engineeringtoolbox.com/temperature-density-petroleum-lubricating-oil-lubricant-volume-correction-ASTM-D1250-d_1943.html

The volume difference correction at 0c or 32f and 125c or 125c or 257f, starts at .9 and ends at 1.075, this volume on a 10 quart system is .2% or 1.155 cubic inches, or about 19ml. I will stand with my original statement. I would posit very few 911s are used at 0c, and if you increase the temp to 85c or 185 when the thermostat for the front cooler opens the difference is even less. This is from your provided charts, the 3rd chart on the page:

https://www.engineeringtoolbox.com/temperature-density-petroleum-lubricating-oil-lubricant-volume-correction-ASTM-D1250-d_1943.html

[brshap]

Originally Posted by ClickClickBoom

The volume difference correction at 0c or 32f and 125c or 125c or 257f, starts at .9 and ends at 1.075, this volume on a 10 quart system is .2% or 1.155 cubic inches, or about 19ml. I will stand with my original statement. I would posit very few 911s are used at 0c, and if you increase the temp to 85c or 185 when the thermostat for the front cooler opens the difference is even less. This is from your provided charts, the 3rd chart on the page:

https://www.engineeringtoolbox.com/temperature-density-petroleum-lubricating-oil-lubricant-volume-correction-ASTM-D1250-d_1943.html

Not to belabor the point but I find this stuff interesting.

So if you take the volume correction factor of 1.0 at nominally room temp your 10 litres=10litres at startup say. With the volume correction factor of 1.075 lets say nominal operating temperature you would have 10L*1.075=10.75L , and increase of 7.5% volume. A not insignificant difference.

Can you explain how you arrived at your numbers? I don't follow.

[PSManring]

Originally Posted by MBAtarga

What engine are we talking about 3.0, 3.2, 2.7 ?

This is a 2003 C4S with a 3.6L.

[PSManring]

Originally Posted by ClickClickBoom

Differential Compression tests are primarily a diagnostic trend monitoring device. “Pooling under intake” tends to indicate a oil leak in the oil venting system. Beware, second opinion before tearing engine down.

I will get a second opinion before investing a TON of cash! I have not been able to reproduce the symptoms that I got at the track.

[PSManring]

Originally Posted by JSV798

Perhaps you just overfilled with oil and extra heat of track event caused oil to expand, leading to spillage. I never fill higher than halfway between marks on dipstick, checked with engine warm and idling.

With the High RPMs and a full reservoir ...??? I will take your advice on the refill amount.
Thanks

[PSManring]

Originally Posted by Trackrash

Let me see if I got this correct. The engine blew out some oil, and the mechanic did a compression, leakdown, and borescope? Not sure how those tests would find the source of the oil leak.

Did he check the oil level or the tank vent setup?

Leak down means little with out knowing where the air is leaking. Scoring on bank one? What does that even mean? I could be wrong, but it sounds to me like this mechanic is looking for work.

He said the scoring was on bank 1 1-2-3 cylinders was normal for a car with 98,000 miles and that cylinder 2 had the leak down. Will not the scoring (grooves on cylinder wall) on cylinder 2 allow oil to leak through/ by the piston rings?