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      11-19-2018, 02:20 PM   #1
speedbunny
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piston surface

I have 150k miles, looked through the valve cover with a borascope to see inside. Didn't expect to see it so black. Is this normal on our cars with 150k miles? My oil consumption is around 3 quarts / 5000k.
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      11-19-2018, 02:41 PM   #2
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If you cleaned the carbon off it would be back soon.
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      11-19-2018, 05:57 PM   #3
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Quote:
Originally Posted by speedbunny View Post
My oil consumption is around 3 quarts / 5000k.
Thtaa almost a full oil change every 10k kms. A bit excessive, no?
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      11-20-2018, 07:25 AM   #4
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The tops of pistons don't stay shiny and new looking, especially in engines with such high mileage. Some carbon buildup is normal.

That's pretty excessive oil consumption and given the appearance of your piston crowns I'd say your rings are worn out. Your engine is tired. Keep running it and enjoy it as long as you can or rebuild it/replace it with a lower mile engine.
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      11-29-2018, 03:31 AM   #5
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does carbon look like this upclose? or am I looking at deformed piston surface.. I can't tell how magnified this is.
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      12-04-2018, 09:23 AM   #6
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looks like a lot of pre-ignition has occurred in that engine. You get enough oil in the combustion process and it reduces the effect of the octane which can make it easier for pre-ignition.
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      12-04-2018, 01:29 PM   #7
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If so, maybe injectors could be culprit? thanks for the observation.
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      12-04-2018, 03:20 PM   #8
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If it's above avg oil consumption it will either be rings or valve seals. A compression test can tell you if you have a good seal around the rings.
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      12-04-2018, 07:24 PM   #9
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valve stem seals? sorry im a mechanical newb.
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      12-04-2018, 08:59 PM   #10
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Hard to tell from a close up shot.

All of the s54's I've dismantled have a coating of carbon on all of the piston crowns.

Try using a fuel additive like Techron more often. I throw a bottle in every oil change.
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      12-05-2018, 03:07 AM   #11
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ok, will do.
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      12-05-2018, 09:58 AM   #12
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Quote:
Originally Posted by speedbunny View Post
valve stem seals? sorry im a mechanical newb.
Not a problem, everyone has to learn somewhere. Part #6, seals off the valve guide so excessive oil doesn't seep down into the intake/exhaust track in the head.
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      12-05-2018, 01:32 PM   #13
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oh thank you for the diagram, I was actually thinking valve stem seal was something else had you not shown me the diagram. Yikes 93$ for seals!
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      12-05-2018, 02:15 PM   #14
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Sorry my mistake



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Last edited by Dave07997S; 12-05-2018 at 03:05 PM..
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      12-05-2018, 03:43 PM   #15
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Quote:
Originally Posted by speedbunny View Post
oh thank you for the diagram, I was actually thinking valve stem seal was something else had you not shown me the diagram. Yikes 93$ for seals!
Buying the seals is the easy and cheap part of changing them. Labor will be a lot more. I would leave well enough alone.
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      12-07-2018, 01:30 AM   #16
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checked the valves. They are very clean with no dirt/oil around them. I think its my rings..Will do compression test.
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      12-07-2018, 09:13 AM   #17
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Compression test will not tell you if the oil control ring is doing it's job. I've also never seen a valve stem seal issue on an s65 or s85 that hadn't been "rebuilt" (meaning half ass taken apart and put back together).

You might consider looking at PCV related things too.
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      12-07-2018, 10:27 PM   #18
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i thought the point of the compression test was solely for piston rings?
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      12-08-2018, 01:11 PM   #19
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Hi,
There are two different tests you can run:
* Compression test: Where you measure the amount of pressure build-up that the piston does on its stroke. An adapter with a hose is screwed in instead of the spark plug, and you use the starter motor to go through 3-4 strokes for each cylinder.

* Leak-down test: Where you measure the flow and pressure drop of air injected into the cylinder from your air compressor. While doing this test the engine is not moving, and you set it to a position where the valves are not open. The leak-down tester also screws into the spark plug thread. The equipment has an air regulator and two gauges.

You can usually buy both these testers from Ebay for under $100 each if you are into DIY, but it wouldn't cost you more than 2 hours labour to let a workshop do the testing for you either. There would be a few tricks to get correct readings, and diagnose correctly, so could be best to let a workshop do it for you.

Cheers,
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      12-08-2018, 02:23 PM   #20
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I think it will be more than 2 hours labor to test 8 spark plug holes and rotate pistons. And there is wait time on the leak down.
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