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First or last Porsche? White smoke issue...

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Hi there,

first, sorry for my english, I'm one of those from Quebec, Canada where we got over 85 inches of snow so far this winter (french canadian).

I've been driving Subarus for +/- the last 10 years (mainly all turbos, Outback, Forester, WRX, Sti). I had LOTS of fun with them. I now decided to try a Porsche. I own a 996 2001 C4 convertible since a couple of days. The car has 60,000 miles (130,000 kms) on it, still in very good shape. Very proud of it, until yesterday.

I had a nice small ride with my 2 kids yesterday night (4 and 6, just enough room for them!!). It was the first ride, +/- 10 miles ride.

Back in my garage, I've restarted the Porsche and noticed a huge amount of white smoke off the exhaust. I've opened the engine bay. My coolant was down for +/- 2 liters (+/- 60oz). It was full, verification was made before departure. Garage floor completely dry, before and after the ride.

I've then decided to look on the net (mainly this forum). I saw many posts about AOS. I'm still however not sure if a bad AOS would consume that much coolant. I expect this to be a more serious problem. Head gasket maybe? With only 60K miles on it, this would be surprizing unless the car would not have been well taken care of before.

Engine ran smooth. I've started it up again today. Again, lots of smoke in the garage. Small hesitation 1 second after it was started, ran smooth after for 10 seconds.

Not sure if I should drive the car or not at this point. Even to bring it to my mechanics at 8 miles away.

Anyhow, I will order a new AOS to replace it after what I read. I hope this will fix the issue. Thanks to all of you for the various DYI, very helpful.

Also, thanks in advance for your comments. I will keep you informed once the AOS changed.

I hope I will be able to run the car this summer and have fun with it. Feeling is great, so far!!!

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To further confirm your diagnosis of a bad AOS, try to remove the oil fill cap while the engine is idling. If the AOS is bad, the oil fill cap will be hard to remove because it is under excessive vacuum. If the AOS is in good shape, you should be able to remove the cap without much resistance.

Also check the throttle body to see if there is a heavy coating of oil. A very slight coating is normal.

If it is the AOS, do not drive the car as you could cause considerable damage if oil is then sucked into the combustion chamber and then cylinders because the pistons cannot compress the liquid (i.e., the oil).

Regards, Maurice.

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If there really is a problem why not have it towed to a mechanic and diagnosed? Maybe there isn't a problem and coolant level can fluctuate slightly depending on engine temp. Throwing parts at a vehicle and guessing isn't the the solution.

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I had exactly the same problems, much white smoke on start-up, lasting for two to three minutes (seemed like forever). I had no problems removing my oil filler cap and feared the worst.

I purchased a new AOS and set about fitting it. When I stripped down the inlet system there was a huge amount of oil in the plenum - more than you could possibly expect to find.

The original AOS looked fine, but when everything was rebuilt the white smoke disappeared and has never come back.

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I Will replace the AOS. There is effectively vaccum from oil fill. I may have a separate issue with the coolant, it may not have anything to do with the AOS/smoke. I will have the radiators/hoses verified, I think I may have a small leek... The challenge is now to find a couple of hours to change the AOS!!!

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If your expansion tank has never been changed it might be leaking. The tank sits above the HOT muffler and cooks until it gets brittle and cracks on the bottom. Often the crack is small at first and only leaks when it is under pressure while the engine is hot. Look in the area under the shelf for signs of leaking.

Also look at the bottom of the water pump.

If your blue cap ends in a number other than -04 get a new one. They are under ~$20 in the US.

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It seems that I will have a couple of interresting hours tomorrow night as I will begin the work. Thanks for the suggestions, I'll verify the expansion tank and the blue cap.

I drove it to the garage where I'll do the work. The oil pressure gauge was travelling between 2.5 and 4. Check engine light finally came on. The exhaust was smelling a lot all the way (wife followed me, no important smoke though). Let's hope for the best!!

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I still wonder if I will be able to make it w/o lowering the engine a little. It is a C4 convertible, I think there's a little less room in the engine bay on convertibles. Right?

BTW, it is -20°F this morning here in Quebec (-29°C). Not necessarely a good day for a ride in a convertible!!!

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6 hours later, almost done. Lots of oil in intake. We've wasted our time trying to remove the coolant tank, w/o success. Then decided to lower the engine, everything became more simple. Let's see what will be the conclusion tomorrow!

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fpb111;A bit off this present topic but while we are waiting for Monsieur Garwood74 to fill us in on his repair, I have never seen a 'Metropol blue' interior with AS as you have. Would you mind sending us a picture of your interior if that's not too demanding? Is this a color that is only avail in a cab 911? Thanks very much!Garwood74;Comment ça va?Martin

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Job done! AOS was the main problem. There was also a leak from a weak hose clamp near the right front rad. So 2 different issues. I feel that engine sounds and runs better now. Didn't go for a ride yet, will do tomorrow. I'm sure I'll have a better feeling vs my first rides in a 911 a couple of days/weeks ago.

Still not a good evening for a ride in a convertible; -40 degrees with the wind factor here in Montreal (F or C)!!! Tu t'ennuies du Québec Martin??

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Garwood74: Félicitations pour ta besogne d'AOS, Simon! Oui et non à ta question! My pleasure to tell you more some other times. On such a cold day like today in Montréal, it is nice to live on the rainy West Coast (+5C today). Back to the AOS, if you can take the time to explain a bit more on the approach you took to do this job, it would benefit a few of us in the near future. As my C2 is approaching 90K miles (143k kms at this time), I'm pretty sure it is still the original AOS. The fact that my drive-to-work commute is not very long, likely doesn't help either on the AOS department. So far so good, though!At the present time, I'm dealing with a pass. inner door latch replacement (window not coming down and interior lights not coming on when pass. door open) and a speaker board that is falling apart due to a vapour barrier (liner between door metal & door panel) that was badly damaged by a previous owner's not so brilliant work: board and speaker have to be replaced as well due to corrosion.fpb111: Many thanks for posting these pictures. This metropol blue goes well with Arctic Silver, I must say and rare to boot. Nice aerial shot of Teddy at the helm! Cheers!

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To replace my AOS, Isimply used the DIY from Hobbes (in the DIY forum). It was great help!!!

As mentionned, I was not able to take the coolant tank out of there. Instead, I've lowered the engine a bit and everything else was easy.

There was a coolant hose connector ( 996 106 226 51) that was completly dry... This should be purchased and changed, no question!! I wonder if a small plastic piece form this part going in the coolant would generate a AOS problem... One thing for sure, not too god to have plastic parts in the coolant system!!!

Next step for me: abs/PMS lights comes on after a couple of minutes (everytime). I will have this checked, probably a sensor or the brake switch.

Hopefully this one will be an easy fix!!

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Merci Simon! I did my pass. door latch this weekend and replaced the speaker (rusted and broken internal wire) and board holding it, plus the liner between the panel, speaker board and the door metal. I got the liner (vapor barrier) from an Independant (indy as often referred to by the Renntechers) dealer in Vancouver. It costs me $90. but it is well worth it. It shapes beautifully to all of the nooks and crannies of the door and provides superb insulation from outside noise. Made by Sofitec, a french company. The old liner was all broken up and totally unusable: Someone had been there before me.Now I have a properly working window (goes down by a couple of cms when I touch the door handle and goes up in its own slot by the same amount when I close the door), interior lights come on when I open that door and, finally an alarm system that does not beep twice at me when I unlock the car. The fact that the car blinked twice when you lock it and once when you unlock it was a nice surprise to me yesterday, since that door latch had not been working fully or properly since I bought the car last April.C'est l'fun quand ça marche, n'est-ce pas mon ami (Great, when things work the way they should, my friend)!? Salut!MartinPS If anyone wants more info, I took a few pictures of old and new latch, door work area and microchip involved, which appeared to be not broken, but well worn out from rubbing on the latch internal cam.

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  • 1 month later...

Update: Check engine went on again. One cat have beed severely damaged because oil went in it (certainly due to the AOS failiure). Dealer in Canada is asking 2,500$ per cat.Found 2 used cat for 600$ (perfect sape, from a car with 40,000 miles on it). Those used cats are impossible to find, at least for the 3.4L. Seems easier for the 3.6L...

This means an AOS failiure must be changed rapidely to avoid this.

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