greg2390

I own a 2003 audi a6 3.0 quattro that I bought back in september 2010. It has roughly 150,000 miles on it. When I bought it the dealer had the catalytic converters replaced on it because the check engine light was on when I bought the car. Since then I have had the oil changed (full synthetic), transmission flushed, and the timing belt service done. Also since I have bought it there has been white smoke coming out of the exhaust. We cannot tell what this is coming from. The temperature levels on the engine are fine, oil temperatures stay around 220-250, and all my fluid levels have been checked by a mechanic and they are all fine. One thing that was noticed, although it hasn't affected it at all was when the timing belt service was done the mechanic took off one of the head gaskets and said there was some actual water in there (it did not look like antifreeze or any other fluids), he emptied it out and put it back together. Any reason this smoke is coming out or what I should have done about it? I also have recently used STP fuel cleaner twice when I filled up with premium fuel, and no difference.

blueS4

White "smoke" often indicates a leaking head gasket, since it's actually steam (water and / or antifreeze) that's coming out the tailpipe. If your mechanic has already looked into the engine and hasn't seen any sings of antifreeze (the engine oil should look kind of like a chocolate milkshake if it's contaminated), then you may have just a little water problem.

If the car isn't driven very far / hard (so it doesn't get fully warmed up) or sits for prolonged periods of time between drives it's not particularly uncommon to experience the white "smoke". It's usually due to some water condensing inside the engine, but it shouldn't last too long after it's warmed up and driving.

Since you've checked several items and can't find anything amiss, you should check it thoroughly after a longer drive. If you're still getting white smoke out the tailpipe after a 20-30 minute run (with the engine under some load) then I'd suggest you should check again for a head gasket leak. If it disappears after the run, then it was likely just some water condensing. Just remember that the "smoke" will likely continue to reappear if the driving conditions that the car is used under continue the same way.

Good luck!

greg2390

The mechanic that works on it lives about 30 miles away from me, which im going 70 the whole way there to see him, and it still is having white smoke come out. If it was a a head gasket do you think I would have noticed something more serious happen by now, I have noticed it for over 2 months. Also, if it matters, I live in eastern NC, and for the most part since November the weather around here has been cold, freezing most nights, and most days of the week below 45 degrees.

blueS4

Temperature can / will play a factor. Some parts of Canada will frequently have months of temperatures that are below the freezing point, so white smoke coming from the tailpipe of every car is a fairly common sight.

If there's no sign of antifreeze contamination within the engine oil after 2 months, then I would doubt that you've got a head gasket leak. During colder months it can be difficult to determine where the white smoke is originating from. You could have some water vapor inside the exhaust system itself, which could produce a similar appearance once the exhaust gets hot.

My best thought would still say to run the car at higher rpm (after all the fluids are fully warmed) make sure everything gets nice and hot - 20 minutes or so in a lower gear or two should suffice - vary the rpm. The idea is to burn off any water that may have condensed inside the engine or exhaust. Continue to drive it normally for a similar amount of time and then see if the white smoke is still present. If it isn't, or is greatly reduced, then you likely just haven't been driving the car frequently enough for longer drives and water has been condensing. If the white smoke increases, however, then you should revisit the leaking head gasket scenario.

mksu19

Condensation can play a part especially if the car has been (mostly) driven in short intervals.

greg2390

Thats what I thought, but I figured the STP fuel cleaner would have gotten the condensation out of any lines or the fuel tank.

blueS4

Any condensation collecting inside the engine or exhaust isn't likely coming from your fuel, it's condensing because of differences in temperature between the air and the metal parts. Water vapor in the air condenses on the metal and unless it's completely burned off, the resultant white smoke (ie. steam) continues to be released from the tailpipe.

It's easier to see the same effect when you let your car sit for a while, your iron brake discs begin to develop a layer of rust on their surface. This is basically the same reaction, whereby a little water vapor is condensing on the discs and the bare metal begins to oxidize.

greg2390

My mechanic said "It seems you may have a plugged crank case vent, hose or siphon jet pump issue causing the smoking issue" since my coolant and antifreeze levels haven't gone down. Has anyone had any experience with this and what costs I may be looking at? He wants to drive it to inspect the hoses and levels again before we go through the trouble of replacing them too.

blueS4

Usually a plugged crank case vent would produce a rough idle or possibly stalling, but you haven't mentioned any issues with that, so I personally wouldn't be leaning that way. It's entirely up to you, but I'd try to burn it off first and see if that works.

greg2390

Do you think driving 70 mph for about 30 minutes 2-3 times in one week burn it off? I did this while driving to my mechanic about 2 weeks ago