560 SEC oil consumption - Mercedes-Benz Forum
 
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post #1 of 5 (permalink) Old 10-25-2018, 09:09 AM Thread Starter
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560 SEC oil consumption

Dear MB enthusiasts,

I'm running out of possibilities to explain increased oil consumption of my 1987 560SEC especially at highway speeds (around 3 liters for every 1000km). My first guess was the valve stem seals but the spark plugs are dry and light brown. Piston rings are another possibility but I'm having perfect compression on all eight cylinders (about 9kg).

There are no leaks that would explain such an amount of oil being lost and I don't notice smoke coming out of the exhaust either (except grey smoke under hard acceleration at highway speed which I suspect is just burnt gasoline).

Am I overlooking something?

Your suggestions would be much appreciated.

Tempur
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post #2 of 5 (permalink) Old 10-25-2018, 09:57 AM
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Quote:
Originally Posted by tempur View Post
Dear MB enthusiasts,

I'm running out of possibilities to explain increased oil consumption of my 1987 560SEC especially at highway speeds (around 3 liters for every 1000km). My first guess was the valve stem seals but the spark plugs are dry and light brown. Piston rings are another possibility but I'm having perfect compression on all eight cylinders (about 9kg).

There are no leaks that would explain such an amount of oil being lost and I don't notice smoke coming out of the exhaust either (except grey smoke under hard acceleration at highway speed which I suspect is just burnt gasoline).

Am I overlooking something?

Your suggestions would be much appreciated.

Tempur
I just replaced the valve stem seals on my 560 and it appears that my oil consumption has dropped to zero. I don't have enough miles yet to be absolutely certain but it sure looks good at this point.
I was not able to detect smoke coming out of the exhaust but I used to have little black dots on the concrete below the tailpipe frequently. Since the valve stem job those black dots no longer appear after a start up.
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post #3 of 5 (permalink) Old 10-25-2018, 08:43 PM
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My guess is also valve stem seals
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post #4 of 5 (permalink) Old 10-28-2018, 05:07 PM
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Before I redid the heads I changed the valve seals and fiund the old ones to be very brittle. The cost of these are negligible (lot of work though) and I doubt its rings. If it does not leak oil then its the seals
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post #5 of 5 (permalink) Old 10-29-2018, 04:43 AM
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Leaky valve guide seals will often show up as blue smoke under heavy engine braking. If you can get someone to follow you, run the engine up to high speed in the lowest gear you have, then close the throttle abruptly and let the engine slow the car. The high manifold vacuum pulls oil past the seals and you should see blue smoke in the tailpipe.
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