Smoke likely due to valve guide, damaged seals

Hey there, time traveller!
This article was published 07/09/2007 (6770 days ago), so information in it may no longer be current.

QUESTION — In 2005, my wife and I purchased a V-6 2006 Hyundai Sonata. Last spring, a cloud of grey smoke would come through the exhaust occasionally when the car started. We took the car to the dealership but they couldn’t duplicate what happened. At that time, the car had only 9,000 kilometres. They suggested that without proof, they could not do anything for us. They suggested we monitor fluid levels and indicated it would be helpful if we were able to videotape the problem. They also asked us to drive the car as often as possible to get some miles on it.

The problem seemed to go away but returned about a month ago. I videotaped the startup. The car currently has 13,000 km. Oil and coolant levels were between the add and full marks.

Again the dealership was unable to duplicate the problem. I also provided the video to them and they suggested we continue to monitor fluid levels. This time, with the video, I thought they may have been able to provide a solution. I would appreciate any advice on resolving this problem.

ANSWER — I viewed your video. The smoke is heaviest at initial startup and quickly disappears after a few seconds. This is typical of either a coolant leak into a cylinder or oil leaking past valve-guide seals.

A coolant leak will cause the smoke to be whiter and it may have a semi-sweet smell. The engine might also run rough for a few seconds at startup because the coolant may have fouled a spark plug. I don’t think the smoke from your vehicle is caused by a coolant leak, but removing the spark plugs will help diagnose the problem. Coolant leaking into a cylinder will clean the carbon off the spark plug and the top of the piston.

I think the smoke is caused by oil running down the valve guides when the engine is stopped for several hours. Seals on the valve guides limit the amount of oil in the guides. Because your vehicle has low mileage, I suspect one or more seals were damaged during initial engine assembly or there is a bad valve guide in the cylinder head. If the problem is only seals, it is a relatively minor repair that can be done without removing the cylinder head.

The dealership should be able to diagnose this problem fairly easily, but they do like to verify a problem before repairs are made. Your videotape should be enough, but leaving the vehicle at the dealership so it can be started several mornings should allow them to see the problem in person.

QUESTION — Last winter, on rare occasions, my wife’s 1998 Chevy Malibu wouldn’t start — it wouldn’t turn over and the “anti-theft lock” light on the dash came on. After a 10-minute wait, the car would start fine and the light goes out. Now it’s starting to do this about every second day or so.

We had it to the dealer a couple of times. They are talking about changing the key and cylinder in the ignition. I just wondered if this sounds right to you, because they want about $350 to do this. Is there a way to bypass this system or have it disconnected? I hope you can help me out

ANSWER — Your car has a PassLock anti-theft system. A magnet on the cylinder assembly rotates past a sensor on the outer cylinder housing. This sends a voltage to the body computer and if the correct voltage is sensed, the body computer will send a data signal to the engine computer to crank the engine and enable fuel injection. There is also a second sensor on the housing called a tamper sensor, which sends a signal to the body computer if the cylinder is broken and turned too far.

I haven’t seen many problems with the key and cylinder assembly or the anti-theft sensors. Usually the problem is with wiring connections either at the lock cylinder assembly or at the body computer. The 10-minute wait period you are experiencing is a programmed “time out” if the wrong voltage is sent to the body computer. This would suggest a bad electrical connection.

Also, check to see if a remote starter has been installed. Remote starters connect into the sensor wiring to duplicate the signal. I have seen several cars with very bad wiring connections on the remote starter system that have caused problems.

Jim Kerr is an experienced mechanic, instructor of automotive technology and member of the Automobile Journalists’ Association of Canada. You can e-mail questions to Jim at the address below.

kerr.jim@sasktel.net