Michael Gibney

Wet and lousy weather here in Eastern Australia -- and after a 2000k run last weekend (was great fun -- 10 hours each day on twisty roads) the oil filler tube has a good "dollop of cream" from the condensation.

Engine oil is clean on the dipstick -- no water contamination.
Water/coolant is clean in the header tank -- no oil contamination.
88,000 k engine no previous history (known) of problems.
Runs really well.

So... looks like nothing more than condensation -- I accept that as "normal" in the weather we are having...

But -- could I have an engine "breathing" problem? Is there a valve or "crankcase air suck into the intake system" that could be blocked or faulty?

All suggestions gratefully accepted.

Regards

cdodkin

Had exactly the same 'feature' running a 1000 miles round trip around Northern Cal one winter.

Lots of rain, cold conditions, gunk in the filler-tube when I got home

Actually took it to the local stealership to check it out and drop the engine oil - everything was fine.

So it's just a feature by the looks of things.

Might be worth dropping your own oil to be 100% sure - small price to pay for peace of mind

ivangene

seems counter intuitive...

my thoughts are that an internal combustion motor (aka a vacuum pump) which normally condenses water on the inside due to expansion but which once becoming warm, burns the water out (causes it to evaporate) thus cleaning out the water. The fact that after a long run there is any water left seems backwards. (even in a moist environment) The way most engines accumulate water is by not getting hot enough, long enough to burn the water out.

Is this something you have checked prior to your trip? Or was it the first time in a while that you opened that up?

In my case changing the AOS resolved my little condensation (aka - creamy fill tube) - if this has never happened before, check it again in a week of "regular driving" and see if it is gone? Changing oil, is OK, but if its not due, the little moisture (I presume its little because there wasn’t panic in your thread) shouldn't hurt while you investigate the root cause.


OH - by the way the AOS (air oil spearator) is a place your engine "breathes" - to answer your question.

Michael Gibney

Thanks Dodkin and Ivan.

I've had the car for about 10K
Filler tube clean when purchased.
Had the dealer do a full service just after purchase.
At that service dealer left the oil filler cap off (hard to beleive) and it ran crappy 'till I looked and put the cap back on -- about 250k's later -- then was still rough and unresponsive for about 200k's -- then came good -- 'suppose it was the computer adjusting itself after struggling with an open crankcase.

Then after about 5000ks I noticed the oil was down two bars on the dash gauge so -- with it warmed up to hot running temp I used the dipstick -- confirmed it was a bit low -- topped up with 1 litre -- was full on dipstick but one bar over on the dash gauge.

At that time -- 5000k after the dealer did the oil change -- I noticed the cream -- about 2 teaspoons in total -- I read the threads here and was not worried -- carefully swabbed it clean.

Then I looked in the filler cap a few times and always noticed numerous (50-100 hard to say) small (1/8th size of matchead) droplets of water on the inside of the filler cap lid and again the two teaspoons of creamy mess -- mostly in the tube.

Then after the abovesaid 2000k fun drive I checked again this evening and no droplets of moisture -- just 3 to 4 teaspoons (that's an increase) of cream.

It would be interesting to know the science of it -- as you say Ivan -- it is counterintuitive -- perhaps when the engine is running in damp weather the crankcase "air" is a mix of oil and water vapour and they mix and condense on the coolest part -- being the top end of the oil filler tube -- and although the droplets of moisture I have seen are similarly condensing in the cooler part of the system they do not magically turn into the cream -- they are different "product".

So -- can a better engine crankcase ventilation system remove the vapours (oil and water) and therfore stop the cream forming?

Is there a way of checking my present crankcase ventilation/suction system?

Is there a way of adding a breather to the filler tube?

Any ideas on upgrading the crankcase ventilation system? (that is only if I have correctly understood the "process")

Regards

ivangene

ok - the oil sometimes runs a bar or 2 down on the electronic guage, I know you confirmed with the dipstick, but not being right at the top isn't bad, in fact for performance driving I have read that it is advised to not have it completely full...

dealer forgot the oil cap... yea, it ran bad!! - and yes the computer was confuse. it should have been re-set by the dealer via computer before driving it (not that it caused issues, but just because its stupid of them to have caused the problem, and they should have fixed EVERYTHING when they solved it)

you sound like a good candidate for a new AOS to me. take some picutres of this next time it shows up. 2 teaspoon (now more) says there is a problem IMO and that is your suspect part. There are ways to diagnos it. Is the car under any sort of warranty? If not we will try and isolate the cause with you.

if the AOS needs replacing, its a fairly involved job. Nothing really "hard" just a LOT of parts to remove to get in there. There are 2 aproaches (1) from the back (the intake manifold has to be removed and motor lowered) (1) from the tranny side (the transmission has to be removed) Neither is too tough for someone with some experience, but neither is easy...

Michael Gibney

Thanks Ivan.

I can do most tech work -- but am unbearably slow! Was a pro tech on Alfa's and Fiats about 30 years ago -- that WAS interesting.

Just did a search on AOS and saw the following -- seems to cover the subject well...

******
The Engine oil air separator directly affects the engine crankcase atmosphere because basically all Porsches from 1980 on including the current 986-987-996-997-Caymen & Cayenne engines are all positive crankcase type systems meaning the engine crankcase has vacuum supplied from the intake manifold to collect and burn the residual combustion by-products or blow-by in the crankcase by running it through the engine again, basically to lower the overall vehicle emissions.

On most occasions, when the oil separator fails, intake vacuum in the engine crankcase rises to an unusually or abnormal rate and more likely than not ends up drawing engine oil into the intake system usually fouling spark plugs and even possibly causing damage to the oxygen sensors (O2), catalytic convertors and even possibly various other sensitive fuel injection components.

Interestingly enough, the only way to test the oil separator is to periodically test the engine crankcase vacuum with a water filled Monometer AKA an ultrasensitive vacuum gauge. On BMW’s and Porsche’s, the engine crankcase vacuum is normally around 4-7” (Inches) of water. When these oil separators fail the crankcase vacuum can rise to 9-12” and even higher depending on the extent of the failure.

When the oil separator is starting to fail on Boxsters (986-987), generally you will start to see a substantial amount of smoke from the exhaust tailpipe. When the oil separator finally fails, the engine exhaust smoke can reach dangerous proportions that almost look like it was manufactured from an anti-mosquito smoke machine. Unusually enough, on the 999-997’s, when the oil separator fails, it hardly ever creates any exhaust tailpipe smoke, almost being like a silent killer or costly surprise.

On another note, it has been known on rare occasions, that when an oil separator fails that it is possible to cause or create a slightly rich running condition that might turn on the check engine light or CEL.

The only way to know what is/was happening is to check the fuel trim numbers on the OBD-II “Freeze Frame” data and crankcase vacuum to see exactly what’s going on, otherwise your just guessing.

*****

So tomorrow I will see what the vacuum is like and will get back to you -- will see if I can get a photo.

Changing the AOS will be an interesting job -- strange that I look forward to the job -- when the "proper" outcome would be for there to be no problem.

Thanks

cdodkin

There is also considerable discussion around using the car for numerous short trips - and this adding to the 'issue' as the engine never gets hot enough to dispel water vapor in the oil.

Then when you go on a longer run - all of that water evaps out, and if the outside temp is cool, it coagulates at the filler cap.

This is what happened to me - I've not had the issue since, and did not have to change out an AOS.

It's over two years ago now - and no repeat so far - buy equally, I've only been driving in warm SoCal weather since then!

ivangene

I agree, there could be a reasonable running car showing these signs based on use times and temps. That said multiple teaspoons of cream sounds excessive and I personally would at least check for underlining cause. Maybe it just is what it is.... maybe not.

anyone have one of these monometers - or make one, and where have you hooked it up to?

cdodkin

Quick test is to take off the oil filler cap with the engine running - place your hand over the oil filler tube - check for any significant suction on your hand.

Significant suction suggests AOS failing/failed - you're directly experiencing the vacuum from the crank-case that results.

ivangene

but "significant" is a relative term. Acording to the info above we all run 4-7 bar vacuum when its "normal, and with a failure you should see 9-12... if your hand is not "calibrated" feeling a potential minimum 2 bar change is gonna be a bit of a trick....even knowing the differance between 4 and 12 might be hard if you dont have some sort of "benchmark" to compare to.

? right ?

cdodkin

Suggest a search on this forum, and 986 forum on this issue and diagnosis - the vacuum pull of a failing AOS is supposed to be significant, and very noticeable.

Ubermensch

Just as a clarification, the description read 4-7 inches of water, not bar. 1bar is about 400 inches of water. But I agree that a gauge is best way to measure this type of difference.

ivangene

I think the engine stumbles pretty bad when the oil fill cap is removed while running as well (another simple way of knowing) Just imagine a huge intake leak - (though in my case I did not notice the poor running condition)

Like I said I replaced mine and in the Seattle area we often see months of rain - my filler cap is dry... I mean DRY inside and I had the cream before... No where near 2 teaspoons (or 4 after this long trip) which is why I suggested the AOS could be shot.....

ivangene

+1 sorry, you are right - inches, not bar -

Macster

Oil filler tube relatively "cold" compared to rest of engine internal air space and any fumes -- water vapor in this case -- that rise up there when engine hot will cool down and condense and collect under cap.

Be sure oil filler tube cap tight and not leaking. This probably won't account for the cream you see but will account for a oddly behaving engine. If leaking at idle air being admitted past cap significant (and unmetered) and engine controller will have a bit of work to adapt.

As soon as you take off and keep engine speed above idle the amount of air getting past cap drops in significance and engine controller will have to unlearn its adaptation.

As you drive then stop at light engine controller constantly going through this process.

What you might notice is engine a bit rough at light but smooths up. Idle speed might increase a bit over normal.

If it gets bad enough check engine light will come on as engine controller reaches the limit of its adaptation.

Also, while you are there verify coolant cap not leaking. Signs of this are water droplets (condensation) under rear trunk and around/on the rubber seal that fits against the trunk over the vital fluids access bay.

I had to replace both oil filler tube cap (missing this at first caused me to replace a perfectly good MAF) and coolant cap. Both wore out and started leaking. The oil filler tube leaking under engine vacuum and the coolant cap leaking under pressure that builds when hot engine shut off.

Sincerely,

Macster.