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Can lower oil pressue resolve white smoke ?(AOS)


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I replaced AOS about 6000miles ago in my 2001 C4 with 64k miles. But I still get smokes from tail pipe even after a short high rpm run above 5000 rpm (just for a few seconds). I keep my oil level higher than maximum in hopes of relieving IMS problem since I read that low oil pressure can cause premature IMS bearing failure. I was wondering if this is causing an overload on AOS resulting in the smoke. Your advices will be much appreciated.

Edited by triling
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  • Moderators

Oil pressure and oil level are two different things, oil pressure has no influence on the AOS system, but the oil level must not exceed the maximum mark, no way. Put the oil level correct and try again.

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I replaced AOS about 6000miles ago in my 2001 C4 with 64k miles. But I still get smokes from tail pipe even after a short high rpm run above 5000 rpm (just for a few seconds). I keep my oil level higher than maximum in hopes of relieving IMS problem since I read that low oil pressure can cause premature IMS bearing failure. I was wondering if this is causing an overload on AOS resulting in the smoke. Your advices will be much appreciated.

You may still have oil in the intake system, which is slow to come out, and a drop creates a cloud of smoke. As RFM stated, do not run the oil level high, that will only worsen your problems.

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Oil pressure and oil level are two different things, oil pressure has no influence on the AOS system, but the oil level must not exceed the maximum mark, no way. Put the oil level correct and try again

I will do that. Thanks.

out of curiocity. My understanding has been that oil pressure depends on oil level as well. If not so, does oil pressure stay the same regardless of oil pressure before it drops below a level where oil pump cannot inhale the level?

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I replaced AOS about 6000miles ago in my 2001 C4 with 64k miles. But I still get smokes from tail pipe even after a short high rpm run above 5000 rpm (just for a few seconds). I keep my oil level higher than maximum in hopes of relieving IMS problem since I read that low oil pressure can cause premature IMS bearing failure. I was wondering if this is causing an overload on AOS resulting in the smoke. Your advices will be much appreciated.

You may still have oil in the intake system, which is slow to come out, and a drop creates a cloud of smoke. As RFM stated, do not run the oil level high, that will only worsen your problems.

Thanks for the advice. should I wipe out the oils from intake routes or should I leave it till the oil eventually is removed through time?

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If I were you I would remove the excess oil from the sump. Either suck it out through the dipstick tube or drain the entire sump contents and refill with the correct amount. An overfilled oil sump can cause quite a bit of damage as oil get into combustion chambers and then into the cats. Cars like Porsches with horizontal engines are more susceptible to high oil levels than cars with more conventional engines where the pistons move up and down. Porsche pistons move horizontally, so excess oil can rest on the bores and then seep past the rings when the engine is not running. When the car starts this oil unites in the combustion process and blows out as smoke from the exhaust . As other have said DO NOT OVERFILL WITH OIL.

Best of luck.

H

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If the oil level is held between the max. and min. mark, oil pressure will be the same. Anyway, if the level falls below the min. mark, under certain conditions, the pump no longer sucks oil and the pressure drops instandly, no oil = no pressure. It goes without saying that this situation must be avoided in the interests of the service live of the engine. Simply respecting the recommended oil level will already prevent many inconveniences.

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I replaced AOS about 6000miles ago in my 2001 C4 with 64k miles. But I still get smokes from tail pipe even after a short high rpm run above 5000 rpm (just for a few seconds). I keep my oil level higher than maximum in hopes of relieving IMS problem since I read that low oil pressure can cause premature IMS bearing failure. I was wondering if this is causing an overload on AOS resulting in the smoke. Your advices will be much appreciated.

You may still have oil in the intake system, which is slow to come out, and a drop creates a cloud of smoke. As RFM stated, do not run the oil level high, that will only worsen your problems.

Thanks for the advice. should I wipe out the oils from intake routes or should I leave it till the oil eventually is removed through time?

Doing so is quite a bit of work as you would need to remove most of the intake system to do it. It would get rid of the smoking issue, but not knowing your expertise level, you need to think about both the effort to do it and the chance of ending up with vacuum leaks if you don't do it correctly.

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Oil pressure and oil level are two different things, oil pressure has no influence on the AOS system, but the oil level must not exceed the maximum mark, no way. Put the oil level correct and try again

I will do that. Thanks.out of curiocity. My understanding has been that oil pressure depends on oil level as well. If not so, does oil pressure stay the same regardless of oil pressure before it drops below a level where oil pump cannot inhale the level?
The basic answer to your question oil pressure stays the same until there is no oil at the pickup.The pressure will fluctuate with RPM and temperature, that is normal.
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  • 2 weeks later...

If I were you I would remove the excess oil from the sump. Either suck it out through the dipstick tube or drain the entire sump contents and refill with the correct amount. An overfilled oil sump can cause quite a bit of damage as oil get into combustion chambers and then into the cats. Cars like Porsches with horizontal engines are more susceptible to high oil levels than cars with more conventional engines where the pistons move up and down. Porsche pistons move horizontally, so excess oil can rest on the bores and then seep past the rings when the engine is not running. When the car starts this oil unites in the combustion process and blows out as smoke from the exhaust . As other have said DO NOT OVERFILL WITH OIL.

Best of luck.

H

Thank you for the tip. I will remove the oil as recommended.

In the mean time, I wonder if lower oil level closer to mimimum can relieve this smoke to some extent. As Moderator marked, if oil pressure is dependant on rpm but not oil level, this shouldn't worsen lubrication performance to my understanding or else?

Your advice is much appreciated.

Edited by triling
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I never have an oil level that is above the "max" mark on the dipstick, neither do I like to see it too close to the low mark.

Why not get the oil level right and see if it solves your smoke problem?

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  • 2 weeks later...

I replaced AOS about 6000miles ago in my 2001 C4 with 64k miles. But I still get smokes from tail pipe even after a short high rpm run above 5000 rpm (just for a few seconds). I keep my oil level higher than maximum in hopes of relieving IMS problem since I read that low oil pressure can cause premature IMS bearing failure. I was wondering if this is causing an overload on AOS resulting in the smoke. Your advices will be much appreciated.

You may still have oil in the intake system, which is slow to come out, and a drop creates a cloud of smoke. As RFM stated, do not run the oil level high, that will only worsen your problems.

Thanks for the advice. should I wipe out the oils from intake routes or should I leave it till the oil eventually is removed through time?

Doing so is quite a bit of work as you would need to remove most of the intake system to do it. It would get rid of the smoking issue, but not knowing your expertise level, you need to think about both the effort to do it and the chance of ending up with vacuum leaks if you don't do it correctly.

I have some DIY experiences such as starter motor replacement which involves removal of throttle assembly but I have not disassembled the whole intake system. I might as well have it cleaned out professionally. Either way if this resolves the problem I am more than willing to spend some. Thank you.

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Gents,

I am confused about the relationship between oil level and oil pressure.

If oil pressure is only affected at 'below oil pick-up level' and above 'maximum level' and unaffected within correct range, why is oil pressure higher after overnight parking at start-up and starts dropping after a few minutes of driving (even at with proper oil level)? I would like to understand if this is sign of a problem (maybe incorrect oil pressure sensor?)

-> This also brings me to another confusion that oil pressure has no influence on AOS. High oil pressure means more oil being sprayed about in crank case so shouldn't this create more oil fumes for AOS to handle?

I had a short 5 second 'above 5000 rmp' run last weekend sign of smoke reappeared. (and immediately gone when I lifted off the throttle). This is when the oil level is just at maximum mark (measured 2 hours after a run). So I am yet to dig in deeper to resolve this problem. One of the options I am considering is adding a separate Oil Catch Tank. Anyone with this experience, I seek for your advice.

Thank. for your supports.

Edited by triling
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The oil pressure is higher when the engine is cold because the oil is thicker when cold (bounded by the pressure control valve), as the oil warms up it will be thinner and thus, at identical engine speed, the oil pressure drop. Keep in mind that the oil pump generate flow, the pressure is determined by restrictions inside the engine, and bounded/controled by the pressure valve. If the restrictions increase in size by wear, excessive bearing clearance, inner leaking chain tensioners, etc., the pressure will reduce at identical engine speed. Hope it helps a little.

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