brotherman

Greetings all - I'd appreciate people's opinions on this.

My '03 996TT produces a lot of smoke out of the exhaust during startup, with the smell to go with it - if you are next to the car, the fumes are very strong and you can even smell them as you are backing out of the garage and the smoke find its way inside the car through the A/C vent. My buddy commended "it's like a boat when it starts" After 20-30 seconds, the smoke is gone and everything looks fine. The car runs fine and I have no other problems with it.

Here's the pertaining info:

- '03 996TT / 25000 Miles
- Completely stock except a Europipe exhaust addition when the car was new
- Last oil change at 18000 miles (Porsche dealer), Pennzoil 5W-40 Synthetic
- Since, toping it off with Rotella T 5W-40 (because it's the only 5W-40 synthetic oil I could find in the open market)

I'm positive the smoke issue started after the last oil change. I'm wondering if the combination of Rotella / Pennzoil has anything to do with it or if it's completely unrelated and I should be looking at something else. I am thinking about taking it in for another oil change, though it's only been 7000 miles but I wanted to hear some opinions before I take it in and I'm at the mercy of the shop.

Thanks in advance.

ltc

Did you by any chance overfill the oil ?

wross996tt

also, do you cool down before shutdown?

brotherman

I don't cool down before shutdown - I thought that was a myth Then again I don't drive it that hard (she's a garage princess - not enough time to enjoy it!).

Have I overfilled? Hmmm, I go strictly by the on-board computer as far as needing oil. Once it goes down two lines I add the exact amount suggested in the manual, 8oz of oil per line (so I add 16 oz for two lines). Perhaps I should run it one line down?

Thx for the replies BTW.

ltc

Do you have a 'wet' residue on the exhaust tips? Is it an oil smell or a fuel smell?

Macster

Unlikely oil change or even oil mixing has anything to do with smoking upon startup.

Except I have to mention this. Rotella T 5w040 is an oil intended for diesel engines. As such it is specially formulated to deal with the huge amount of soot diesel engines put into their oil. An oil that is formulated to deal with high levels of soot is a very high detergent oil. In a diesel engine that sees very low rpms and has a superior air/oil separator to remove the high levels of oil vapor a high detergent oil can generate this is ok.

In a higher reving gas engine, high detergent oil can result in excessive foaming and high levels of oil vapor in the crankcase. This AOS already a weak point with the Porsche engines might simply be overwhelmed and unable to remove all the oil vapor.

This oil vapor along with crankcase fumes is routed to the intake manifold of the engine and when engine shut off any oil on the intake walls will drain down into the engine and upon next startup cause oil smoke.

Just a thought.

Someone has asked about overfilling. You can try running oil a bar or two below max line.

An oil change might help. If you don't drive car much and use it for short trips oil can build up quite a load of water and unburned gas. This makes the oil more fluid and more likely to seep past whatever it seeps past.

Or the oil can come from the AOS failing to remove all the oil vapor. I touched upon this above regarding using Rotella oil. Anyhow, oil with miles on it will pick up water and unburned gas -- these are common contaminants in oil form combustion. Oil with water and unburned gas more likely to foam and aerate and this puts more oil vapor in crankcase fumes. So much so the AOS can't remove it all and what it can't remove gets routed along with crankcase fumes to intake manifold of engine. The oil vapor will deposit its load of oil on the intake manifold walls and upon engine shutdown this oil will drain down and into one or more combustion chambers where it will result in smoke upon startup.

Now, it is probably colder too. Engine controller likely running engine richer upon cold start. A garage is a confined space so any exhaust smell will seem overpowering as you back out through the exhaust cloud.

Are you possibly mistaking the strong smell of exhaust and possibly now visible water vapor in the exhaust due to colder temperature? I see my 03 Turbo emitting water vapor now that night time temperatures are in the mid to high 40s.

I see an occasional cloud of what I know -- from experience -- to be oil smoke but it is rare.

My 03 gets 5K mile oil/filter changes. I run 0w040 Mobil 1 though this last change I tried Mobil 1 10w-40 high mileage oil even though my Turbo had at the time just 17.9K miles. Next oil change I'm going to use Mobil 1 5w-50 oil.

However, you can use the oil the dealer or some other quality oil as long as it is approved by Porsche for use in the Turbo engine. Just be sure the shop doesn't overfill the engine. If you have dealer change oil pick up a quart or two of oil at the dealer. My dealer's parts counter even carries the little cloth bags you can fit a quart of oil into and tuck it down in the trunk or somewhere out of the way. I like to carry a quart or two in the trunk though I use a small plastic tub to carry the oil bottles in just in case a bottle leaks it doesn't put all into the trunk and onto the carpet.

Sincerely,

Macster.

wross996tt

You should do at least a minute cool down...

This sounds fine to me...some trackers don't fill it to the top.

brotherman

Lewis: No wet residue whatsoever on the exhaust tips. I'd say the smell is reminiscent of fuel more than oil.

Macster: Very educational post - definitely not cold weather related (Florida). Unfortunately I don't drive the car much and when I do it's usually 10-20 mile trips which possibly contributes to the problem, as you suggested.


Thanks to both (and Statman) for the info.

Also I wonder if the Europipe could possibly amplify the problem? I think I have stage 2 (judging from the noise - people can hear me coming in a block away

Dock

I RARELY get any smoke on start up (I honestly can't remember the last time it occurred).

I run the oil level down to one bar above the minimum mark before adding an entire quart of oil. I also idle cool down.

Exhaust = EP2 Loud

Macster

Right. In Florida then smoking not due to cold weather then but the area is known for its high humidity.

Thus with the short trips I bet the oil contains a good amount of water and unburned gas from the short trips.

If I were you before I spent any more time worrying about the smoking upon startup I'd have the oil/filter changed and I as touched upon be sure the engine is not overfilled.

Mention to the service manager you are concerned about smoking upon startup and unless he advises you against this, ask if he would instruct the technician to not fill the engine with oil right up to the max. bar line but a bar or two below.

Then afterwards only add oil when the level gets down to say a couple of bars above the minimum level. Add just enough oil to keep the oil level a bar or two below the max. line leve.

Then see if the smoking upon startup continues.

Of course, if smoking gets worse, engine develops any other symptoms or oil level starts dropping at an alarming rate this suggests the smoking is just another symptom of a more serious problem that needs prompt professional attention.

Unlikely a change in the exhaust system could account for the excessive and consistent smoking...

Except I have to point out that in changing the exhaust system this could have an effect on the amount of back pressure the exhaust system has.

The engine's intake system and valve variable lift and variable valve timing based on a certain range of back pressure. This is especially true at cold start and cold engine idle cause the engine controller uses variable valve lift and timing to reduce cold start emissions and speed up converter warmup.

Reduce the back pressure (or increase it) by too much and the startup smoking could arise from a higher level of unburned hydrocarbons that results from a faster than expected flow through the exhaust system.

Even more so than older engines, these newer engines are very tighthly coupled from intake to exhaust. A change in one area can have repercussions elsewhere.

Would I advise you to revert the exhaust system back to stock? No. At least not yet. I'd give the oil/filter change and a slightly lower oil level a chance to show any improvement.

If the smoking continues though and absent any other source of the symptom the change to the exhaust does move up the list of possible causes.

I would still not advise you to revert back to the stock exhaust unless you can't live with the smoking or simply want to see if the exhaust change has or had any affect. At this point what you do and why you do it up to you.

Sincerely,

Macster.

brotherman

Thx for all the advice. I'll get an oil change next weekend and run it a couple of bars below the top - see if there's a change in the behavior.

Dock

You can let the oil level drop further than a couple of bars from the top.

BuddyG

Slight smoke on startup is not unusual because the motor
is a flat six and some oil can sit in the cylinders and gets
burned on start up. If it is excessive good advice above.

Hawk2109

When was the last time you had your valves adjusted? You may be due.

.02

whiteturbo

The 996 does not need to have the valves adjusted.