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Oil Separator - diagnosis?

Chauch
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Chauch Member

Chauch

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I recently had my 996 C2 serviced at a local OPC and it has come back with advice that the oil separator needs replacing. I have searched the site as much as I can, and the usual signs seem to be smoking on startup or a chirping noise. I have no smoke at all and no noise.

How can I ensure that this work needs doing and what harm does not having the separator replaced cause?

Many thanks in advance....

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wams Member

wams

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Remove the oil filler cap with the car running. Then cover the opening with the palm of your hand to check for suction. You shouldn't have any.

(Wams - 09-07-2008) I have a 2002 Boxster. It once sputtered and white smoke with blue tint came out of the exhaust. Then it was fine for several days to a week. In the meantime I called the local Porsche dealer and talked with a service manager. The service manager told me that there could be an oil separator problem and I should have it checked, before it got worst ... meaning the O2 sensors could be ruined. Well, it was one week too late. The O2 sensors went bad, besides the oil separator problem. The total cost was around US $650 at the dealership.

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Loren Member

Loren

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Remove the oil filler cap with the car running. Then cover the opening with the palm of your hand to check for suction. You shouldn't have any.

(Wams - 09-07-2008) I have a 2002 Boxster. It once sputtered and white smoke with blue tint came out of the exhaust. Then it was fine for several days to a week. In the meantime I called the local Porsche dealer and talked with a service manager. The service manager told me that there could be an oil separator problem and I should have it checked, before it got worst ... meaning the O2 sensors could be ruined. Well, it was one week too late. The O2 sensors went bad, besides the oil separator problem. The total cost was around US $650 at the dealership.

MSRP on a Boxster oil separator is $70.51. So they charged you 6 hours labor for a 1 hour job? (Porsche book time is actually less than 1 hour).

Time to find a independent shop or DIY I think...

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Chauch Member

Chauch

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Remove the oil filler cap with the car running. Then cover the opening with the palm of your hand to check for suction. You shouldn't have any.

Many thanks, started her up and there is certainly suction there so that would explain the diagnosis.

Thank you for the warning on O2 sensors as well - will get it booked in ASAP for the work.....

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svansyoc Member

svansyoc

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Remove the oil filler cap with the car running. Then cover the opening with the palm of your hand to check for suction. You shouldn't have any.

Many thanks, started her up and there is certainly suction there so that would explain the diagnosis.

Thank you for the warning on O2 sensors as well - will get it booked in ASAP for the work.....

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svansyoc Member

svansyoc

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Just a little side note on oil seperators, there should be a very slight negative pressure in the cranckase on a normally asperated engine while idling. The quick test if the oil cap is opened the vehicle should not die emediately or sound as if it has extreme gasping noise, there are gauges to measure this pressure, but a trick that we used in the shop is to use a latex exam glove with a rubber band around the fill tube, it should pull in when started showing slight negative pressure, if it balloons outward the seperator is bad, or if the extreme gasping noise is heard when opening (sometimes it can be even hard to get the fill cap off when this occuring) .

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rp2.5 Member

rp2.5

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Just a little side note on oil seperators, there should be a very slight negative pressure in the cranckase on a normally asperated engine while idling. The quick test if the oil cap is opened the vehicle should not die emediately or sound as if it has extreme gasping noise, there are gauges to measure this pressure, but a trick that we used in the shop is to use a latex exam glove with a rubber band around the fill tube, it should pull in when started showing slight negative pressure, if it balloons outward the seperator is bad, or if the extreme gasping noise is heard when opening (sometimes it can be even hard to get the fill cap off when this occuring) .

Can the AOS be bad and not have smoke???

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RFM Member

RFM

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Yes, it is possible. In this case you have to check the DME "actual values" adaption values reaching rich threshold ( engine takes false air - same symptom as vacuum hose loose/cracked ), in some cases the CEL will come on.

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Chauch Member

Chauch

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Having not had any smoke at all, I am now getting a tiny amount when pulling away and can see a slight oil leak onto the left muffler.

The OPC quoted the job at 8 hours, local Indy has quoted 2 hours labour which makes the job a bit of a no brainer so it is booked in next week.

Thanks for your help guys....

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Chauch Member

Chauch

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I'm curious, 2 hours is very sharp. Are you sure that the indy will replace the AOS complete and not only the rubber bellows.

I thought this too, but did check with them and they have quoted for the air oil mist separator at just over £74 for the part and then stated that the bellows hose may need replacing at the same time for another £10. I also gave them the symptoms and they seemed to agree with the diagnosis....

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Chauch Member

Chauch

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Had the work completed today and what a difference it has made. As soon as I started it up, the car sounds very different and idles so much better. It feels more responsive right through the rev range as well. None of this I was expecting.

The job took 3.5 hours although they also sorted a very leak from the rocker cover in that time so very pleased....

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996 Member

996

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Had the work completed today and what a difference it has made. As soon as I started it up, the car sounds very different and idles so much better. It feels more responsive right through the rev range as well. None of this I was expecting.

The job took 3.5 hours although they also sorted a very leak from the rocker cover in that time so very pleased....

how much did you pay to have the work carried out?

Is there a DIY available on AOS replacement for late 98 996 c2 manual?

thanks

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996 Member

996

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Remove the oil filler cap with the car running. Then cover the opening with the palm of your hand to check for suction. You shouldn't have any.

Hi, when I remove my oil filler cap, I can feel suction when I place my hand over the filler tube, also I hear quite a loud hissing type of noise coming from the left hand side of the engine bay towards the bulkhead and the idle becomes rough.

When I replace the filler cap it all goes away and idle goes back to normal, I assume from your comment that this is not normal and is a sign of the AOS requiring replacement?

I have 98 C2, manual, 44k miles. The reason I ask this is because sometimes I get smoke on startup with quite a bit of water dropping from the exhaust tailpipes and most of the time my car hesitates on turn over - like the starter is sticking, but its not as I've had it tested and doesn't do it all the time, definitely not the ignition switch as I've already changed that. I' ve read on this forum that the AOS could be linked to starting problem.

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Chauch Member

Chauch

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Thedre is certainly still mild suction on the filler pipe with the AOS replaced and the idle still changes slightly when you remove the cap which I am told is normal, and it runs and sounds sooo much better.

From memory including parts I paid just over £300 all in...

Edited by Chauch
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