Need thoughts and advice please: Major headache getting worse

[Clewsey]

Hello all, For those of you very mechanically minded on this forum I'd really value your thoughts and advice on an escalating problem with my 2002 (Facelift) 986 S and to give me your thoughts on my theory. I am not that mechanically minded but have a logical brain at least!

Some background/context:

I've experienced three issues (latest one today) during track sessions ONLY. The car has never experienced any kind of issue with normal road-use (hard or sedate driving). The only thing commonly observed any time has been a very small amount of smoke at initial start-up, then nothing subsequently. Car runs nice and smooth.

Result of first track outing - very small oil leak, cause was an engine crankcase plug/seal. No oil leak prior to track session (check garage floor each drive). Whilst quite bizarre, the plug/seal was replaced, oil cleaned up etc. Further road driving fine and no oil/coolant loss etc. All good again.

Result of 2nd track outing - as above. Exact plug/seal again popped! Specialist ran a series of cylinder leakage tests and all showed good consistent results (3 tests). The AOS was checked and whist the specialist was going to replace it out of the fact these are a typical weak-spot, it was confirmed this looked fine and so wasn't replaced. The concern here (and was discussed after the first instance) was a possible build up of pressure inside the engine and as it popped the exact same one, a real possibility as this shouldn't happen! The specialist used some gasket sealant on the plug to keep it in place.

Car driven hard by both me and the specialist and all fine. Some spirited drives later, no oil leaks and all smooth running. As I'm doing Spa later this year the only way I was going to test it was to take it back on track to see if the problem would come back. Well, it did but in a very different fashion.

Today, after about 5 laps (all fine at this point) I exited a corner and accelerated hard. On doing so, an almighty plume of WHITE smoke filled my rear view mirror, CEL came up (flashing yellow) and at which point I backed off and parked up off circuit. Smoke exiting exhaust.

Things to note. Engine hadn't blown, no rough running pre or post incident. No overheating, no oil loss registered on gauge OR visually dropped on ground. Idling was as smooth as under normal conditions. Track support who was with me were as bemused as I was given the fact the car was still sounding fine. On checking the oil filler cap, there was a lot of pressure/vacuum going on. I drove it extremely lightly 30-50mph for 3 miles and after a few miles, no smoke. The car was recovered home where even after a cold start, not too much smoke was found. The other thing to point out is that my CEL light came on at the initial incident today but on repeated starts doesn't display the CEL message....

My logical theory:

The symptoms of the HUGE white smoke points to an AOS failure. A high build up of pressure (as before) wasn't able to pop the plug/seal because it was fixed in place and therefore found the next weak link as pressure needs to escape after-all. I've read all the usual posts of AOS failure and the symptoms I've mentioned previously all appear. My Porsche specialist wants to give me an explanation but at the moment is quite frustrated. His next move would be to use a scope to go and have a deeper look. However, the car just doesn't show any signs of a major engine issue (other than the smoke) and even that isn't too bad on returning home today.

Looking at a thread on pelican parts, not only did it discuss the AOS failure symptoms at length but then also mentioned that these type of failures are caused by other engine issues (positive crankcase ventilation valve) or PVC getting clogged or broken causing excessive high pressure to build in the engine and then ultimately breaking the AOS. This is one of paragraph of interest from this post:

http://www.pelicanparts.com/techarticles/Boxster_Tech/09-ENGINE-Air_Oil_Separator/09-ENGINE-Air_Oil_Separator.htm

"Followup from the Pelican Staff: The air oil separator is a an emissions control unit whose purpose is to separate fuel vapors from the crankcase and funnel them back into the intake. These units fail over time when the diaphragm inside gets old and breaks. They can also be caused fail prematurely by other components on the engine failing, most noticeably the positive crankcase ventilation valve (PVC). If the ventilation valve is clogged or broken then the pressure / vacuum levels inside of the engine may become very high, and that puts a lot of stress on the air oil separator diaphragm. Typically when people have a air/oil separator failure problem, and it keeps happening again and again, it's often related to the PVC valve. I did a close look at this first. - Wayne at Pelican Parts"

Obviously there is no other explanation that the high pressure causing the same plug to pop each time but I think the paragraph above could be a real possibility as no doubt there is excessive pressure happening. I don't know if the specialist has looked at the PVC but it seems very possible. I don't know how common these break.

If you have any thoughts or other alternative suggestions, I'd really appreciate them. Until the root problem is found, it's hard to make a warranty claim... I just can't now risk doing any more track sessions until this is fixed. It's also costing me a lot of money each time and I'm now getting earache....... say no more.

Thanks very much for any help and sorry for the long post!

Cheers,
Simon

 

[Glyn]

It seems common on these forums for owners to describe smoke from their exhaust as either blue or white, simply because they read that white is OK whilst blue is very bad.
Just to clarify - smoke is blue - its oil burning
White is steam.
You cannot have white smoke at startup from cold- the plume you see is oil burning and it has a tinge of blue, when an engine cools down water forms in the exhaust system, when the engine is started the cats heat up quite quickly, however not that quick to produce a plume - so its oil and that's a fact, water is expelled from the exhaust and within a few minutes any vapour left will exit as steam.

The reason for the plume on startup is from oil and is nothing to be concerned with, its embarrassing to have a premium marque of car that produces a plume like an old banger but its all to do with the boxster engine design, Briefly - there are three cylinders to the left and three to the right - horizontally opposed, oil is pumped around the engine and when switched off oil drips from the upper extreems of the engine back down into the sump, some oil is splattered into the bores behind the pistons - hot oil is very thin and runs easily, if you have the car parked on a slope (left to right or vise versa) oil drips that drip into the bore runs along the bore behind the piston and a puddle forms, when the engine cools the pistons shrink a little and they return to their original shape of slightly oval (This is because all metal expands with heat - if the pistons were perfectly round and a tight fit the engine would seize when hot, there is more metal around the little end - this part is where the con rod connects to the piston - more metal means more expansion so the piston is machined with a bigger gap tolerance to allow for the expansion)
When the engine cools the larger tolerance at the two points on the piston will allow a tiny amount of oil from the puddle behind the piston to creep by the oil control and piston rings (a miniscule amount of oil produces a lot of smoke) and thus oil enters the combustion chamber - hence the plume on start up, obviously engines with greater miles also have greater wear and the effectiveness of piston rings and the oil scavenge ring together with wear in the bore is reduced and therefore will tend to burn a little more oil or indeed smoke on every start up, Park the car on level ground and the plume will be minimised or occur infrequently.

OK, back to the post, Indeed I would change the AOS simply because these fail so frequently and despite examination no one can certify it is working or completely failed, the part is only £60 but a pig of a job to do so an OPC will charge you £500 to £600 for the job, You can fit this at home if you are reasonable with a spanner.

Blowing seals is usually caused by excessively high oil levels or crankcase pressure - unless of course the seal is very old or high mileage in which case they naturally fail.

The AOS should separate the oil mist which is in the crankcase, condense it and return it to the sump, some of the mist is sucked into the throttle body and is burnt by the combustion process, however, if the AOS is not efficient then more oil mist is drawn into the throttle body and will lay in a puddle in the rubber pipes, heavy throttle produces high vacuum when the throttle butterfly opens and this will suck the puddle of oil from the pipes into the engine - hence massive oil plume on hard acceleration.
The AOS is also the crankcase ventilation system / and affects the emissions - so excessive oil mist drawn into the combustion chamber will affect the oxygen levels in the exhaust gasses and this will trigger an engine check light.

Everything you have described would be accountable for by the AOS, Blowing a seal - excessive crankcase pressure - AOS partially blocked
Plume of smoke, excessive oil mist being drawn into the engine - AOS not condensing the mist
Check light activated - resets when engine cooled because emissions are detected as correct by the Lambda sensors on next start

If you read the codes you will find the engine check light was triggered by the lambda sensors.

On a track you are using full throttle for a considerably amount of time more than you would on any public road - so the temperatures in the engine rise producing more oil mist and frothing, high engine speeds held longer than you would on any road - causes more oil froth and oxidisation, more combustion gasses will get past the piston rings and increase the crankcase pressure - which would force the AOS to cope with a much heftier job to do than poottling to the shops.

If its not your AOS then you have a serious problem with scored bores and massive crankcase pressures as a result.

For £60 and a bit of home spannering change the AOS no matter what your experts are telling you - they are wrong

If Pelican told you exactly what you have stated regarding the job the AOS does then they need to go back to school

 

[Richard_Hamilton]

The white smoke and high vacuum on the filler cap are definitely the AOS.

What is the crankcase ventilation valve? I can't say I've heard of that before.

Crankcase pressure and oil pressure are totally unrelated. The plug sounds like it might be a core plug on the main oil gallery. I've heard of them leaking, and even being blown out, dumping large amounts of oil, and causing heart failure! It sounds to me like it wasn't fixed properly first time. I think you may be able to check oil pressure with a Porsche tester, but I very much doubt it is too high, unless the pressure relief valve has stuck. More often, the spring can break, giving low pressure. Even if the tester can't read it, you could put a mechanical gauge in place of the pressure switch to test it.

IMO you have two unrelated issues. I would get the AOS changed, the oil pressure checked, and take it from there.

 

[Clewsey]

Thanks Glyn and Richard for your responses, very comprehensive. Just a few points of clarification though for the record:

- The Pelican parts response wasn't to me directly, but just something I spotted whilst reading a thread of AOS failures.
- The engine had no excessive oil levels
- The original engine seal popped, and the specialist made sure the new one was replaced correctly. I don't doubt this as they are very thorough.

Glyn - just one question. You said the AOS is also the crankcase ventilation system but on diagrams I've looked at, the PVC appears at least to be a different item but connected to the AOS? My train of thought had been that if this is blocked/broken (according to the PP post), then this could be causing the high pressure to build. Pardon my ignorance here, just reading the threads for ideas. The reason I say this is that the AOS has never failed previously, just the same/replaced seal popping each time. This time with the seal "sealed", the pressure has failed the AOS. The plug hasn't popped this time as no oil on the floor.

I don't doubt the AOS needs to be replaced after yesterday as a precautionary thing to do but the excessive crankcase pressure is the worry. I guess getting the endoscope in there is the way to go to prove if there's any bore scoring. I hope this is not the case of course. If I have this would there be other symptoms? The car (up to yesterday at least) felt brilliant and even with this happening doesn't feel any different?

Thanks for your help!

Cheers,
Simon

 

[spyderman]

I've had the same plume of smoke after oil surge on track at Rockingham and one of the new race Boxsters did exactly the same Wednesday at Silverstone. If you're going to track it a lot consider fitting a baffled and extended sump. Until then make sure you don't over-fill with oil - one or two bars off the top is sufficient.

Chris.

 

[Richard_Hamilton]

ORIGINAL: Clewsey

............... but on diagrams I've looked at, the PVC appears at least to be a different item but connected to the AOS? ............

Can you point me in the direction of where it is on the PET diagrams? I'm struggling to find it.

 

[Clewsey]

Hi Richard,

For the life of me I can't find it now - so annoying as I was looking at a clear diagram of the interconnecting parts yesterday. I've given up and will come back and have another go later on.

If anybody else can find it please share

Cheers
Simon

 

[Glyn]

The AOS relieves the crankcase pressure at the same time it separates the oil mist and condenses it, a partially blocked AOS prevents condensed oil draining away - which in turn prevents the mist separation from doing its job, the breather pipe from the AOS connects to the throttle body and when air is drawn into the throttle body that same depression acts on the rubber tube from the AOS - drawing crankcase fumes, oil mist and pressure - which the engine then burns and expels via the exhaust.

There is nothing in your post that should concern you regarding serious issues with the engine - it WILL be the AOS because your description of running in conditions not on a track would not be the case with any serious bore scoring.

I know these cars create paranoia and when something goes seriously wrong its serious money to put right, just relax a bit, change the AOS.
The pressure on you at the moment is more serious than the pressure in your crankcase, simple cheap part to swap out and everything will be sorted.

 

[Clewsey]

ORIGINAL: spyderman

I've had the same plume of smoke after oil surge on track at Rockingham and one of the new race Boxsters did exactly the same Wednesday at Silverstone. If you're going to track it a lot consider fitting a baffled and extended sump. Until then make sure you don't over-fill with oil - one or two bars off the top is sufficient.

Chris.

Thanks Chris. Assuming you are saying or two from the max line? I agree with the extended sump recommendation, something I may do if I decide to keep it going forwards.

Simon

 

[Clewsey]

ORIGINAL: Glyn

The AOS relieves the crankcase pressure at the same time it separates the oil mist and condenses it, a partially blocked AOS prevents condensed oil draining away - which in turn prevents the mist separation from doing its job, the breather pipe from the AOS connects to the throttle body and when air is drawn into the throttle body that same depression acts on the rubber tube from the AOS - drawing crankcase fumes, oil mist and pressure - which the engine then burns and expels via the exhaust.

There is nothing in your post that should concern you regarding serious issues with the engine - it WILL be the AOS because your description of running in conditions not on a track would not be the case with any serious bore scoring.

I know these cars create paranoia and when something goes seriously wrong its serious money to put right, just relax a bit, change the AOS.
The pressure on you at the moment is more serious than the pressure in your crankcase, simple cheap part to swap out and everything will be sorted.

Cheers Glyn, yes a stiff drink was needed last night (and some ear defenders with the other half) []

Bit of an update today.

Started the car from cold, usual bit of smoke. Left the engine idling for a bit. On idle, removed the oil cap with no problem whatsoever. Engine didn't become rough etc. On very light throttle, some smoke but hardly anything to be honest (oily smell).

I took the car out for 5 mile drive with roof down to listen and watch. No smoke at all, and because everything seemed to be fine, I gave it heavier throttle up to 70mph. Again no smoke. On returning home, no oily smell at all, no smoke and at idle removed oil cap no problem.... So maybe the remaining bit of oil etc had been burned off? So, as it stands - the car appears normal again....

I will have the AOS swapped out as you say and I'll still have the specialist look with an endoscope but all appears normal again. I do wonder if Chris's comments on the oil surge could also have been relevant? (my oil level is on the Max line).

Cheers again for your help!
Simon

 

[Clewsey]

ORIGINAL: Richard Hamilton

The white smoke and high vacuum on the filler cap are definitely the AOS.

What is the crankcase ventilation valve? I can't say I've heard of that before.

Crankcase pressure and oil pressure are totally unrelated. The plug sounds like it might be a core plug on the main oil gallery. I've heard of them leaking, and even being blown out, dumping large amounts of oil, and causing heart failure! It sounds to me like it wasn't fixed properly first time. I think you may be able to check oil pressure with a Porsche tester, but I very much doubt it is too high, unless the pressure relief valve has stuck. More often, the spring can break, giving low pressure. Even if the tester can't read it, you could put a mechanical gauge in place of the pressure switch to test it.

IMO you have two unrelated issues. I would get the AOS changed, the oil pressure checked, and take it from there.

Richard, found it. Find the diagram here:
http://forums.pelicanparts.com/boxster-cayman-forum/603481-question-boxster-air-oil-separator.html

 

[Richard_Hamilton]

The parts lists describe it as a "Connection Piece". Are you sure it is a valve?

 

[Clewsey]

From what I've read, it does look that way but I've been told today by an OPC that they rarely fail.

I've had an update today from my specialist. Looks like the Oil Surge scenario is known about but not that well publicised. And it would appear this is the issue. The car was driven hard today on the road and no issue (oil cap easy to remove, no vapour), no oil plumes other than the one on startup etc.

Apparently there is a modified dip stick which alters the level of oil when full, a change to the programing of the oil level sensor and a modified / motor sport oil separator was introduced for the first Boxsters.

So Spyderman's post was certainly on the right lines.

Will update with more news but moving forward now at least []

Simon

 

[Clewsey]

Just a small update on the Boxster.

I've ended up having the Porsche Motorsport AOS fitted in addition to having the oil level lowered to one bar below MAX. The original AOS was fine when it was broken apart so I can only conclude a combination of the standard AOS being overwhelmed and oil level caused the oil surge. According to my specialist, the MS AOS looks much larger and is pretty tricky to fit due to a different design.

I'll be booking a track evening back at Bedford to see if it's now cured. I hope so as the AOS/fitting wasn't exactly cheap!

Simon

 

[Clewsey]

ORIGINAL: Clewsey

Just a small update on the Boxster.

I've ended up having the Porsche Motorsport AOS fitted in addition to having the oil level lowered to one bar below MAX. The original AOS was fine when it was broken apart so I can only conclude a combination of the standard AOS being overwhelmed and oil level caused the oil surge. According to my specialist, the MS AOS looks much larger and is pretty tricky to fit due to a different design.

I'll be booking a track evening back at Bedford to see if it's now cured. I hope so as the AOS/fitting wasn't exactly cheap!

Simon

Mission accomplished. An evening and at least 30 laps (15 consecutive) went by trouble-free I'm pleased to report.

There was some bad news the day after however....... my clutch finally started to fail dramatically. It's lasted longer than I'd expected and at least it didn't spoil my enjoyment Thursday - phew. Now, just the only issue of shelling out for a new clutch, RMS and IMS[]