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Intermediate
Joined: Apr 2019
Posts: 37
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Question
Had my 66 L79 rebuilt about 4 Years ago with 3,000 miles put on the car. When the car sits for awhile it blows out white smoke .When you run it for a while it goes away. What causes the white smoke and what is it? Thanks for your knowledge input.
Safety Car
Joined: Mar 2009
Posts: 4,191
Likes: 951
From: Corpus Christi, TX
White smoke is usually an indication that coolant is leaking into the cylinders from somewhere. Head gasket, intake gasket or valve guide come to mind as possible sources. Oil smoke is usually a bit blue rather than white. You may want to get a whiff of the smoke to confirm. You;ll notice an antifreeze like smell if it's coolant.
If it's oil, most likely source is through the valve guides. You may need new valve stem seals.
If it's oil, most likely source is through the valve guides. You may need new valve stem seals.
Le Mans Master
Joined: Aug 2005
Posts: 6,526
Likes: 1,960
From: Temple Terrace Florida
White smoke could also be benign. It could be condensation collecting in the mufflers and exhaust system. As the heat of the engine hits the moisture, it burns off as steam. If it was coolant in the combustion chamber, some of your spark plugs would be steamed clean. Jerry
Le Mans Master
Joined: Nov 2015
Posts: 7,435
Likes: 2,612
From: Really Central IL Illinois
When you start the car, go go the tail pipe emitting smoke and hold a white paper towel / cloth within an inch or so to the pipe. You can then smell the rag to help determine the emission. You can also stick your finger in the exhaust and see if it is oily or just wet.
Combined with the answers to basic questions:
1.) are you losing coolant?
2.) are you losing oil?
Combined with the answers to basic questions:
1.) are you losing coolant?
2.) are you losing oil?
Team Owner
Joined: Jul 2001
Posts: 21,374
Likes: 1,004
From: Various places in Southern California.
Good chance it's condensation. In addition to the suggestions mentioned above, condensation smoke/vapor dissipates much more quickly than oil smoke. The fact you notice this after several days makes me think condensation is more likely.
One other thing--my car still has the functioning exhaust heat riser with the thermally-activated valve on the passenger side. If the car sits for a while in colder, damp weather that can lead to condensation, I will see vapor coming out of the driver-side tailpipe, which goes away when the condensation is gone, but then when the valve opens allowing exhaust to go out the passenger side pipe, I'll get vapor out of that one for a minute or two.
One other thing--my car still has the functioning exhaust heat riser with the thermally-activated valve on the passenger side. If the car sits for a while in colder, damp weather that can lead to condensation, I will see vapor coming out of the driver-side tailpipe, which goes away when the condensation is gone, but then when the valve opens allowing exhaust to go out the passenger side pipe, I'll get vapor out of that one for a minute or two.
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