Alright guys I've noticed that every now and then my truck will puff out white smoke only on start up after that it doesn't do it anymore while driving. Any ideas?

Thanks guys
Robert

 

Valve seals, or seals and worn valve guides to go with them.

 

It's only on cold starts after it warms up it doesn't do it anymore

 

That's common, but that produces black or very dark smoke.

White smoke is water / coolant. If the poster is seeing white smoke on start up then I suspect he has a head gasket leak or an intake manifold gasket leak. Possibly cracked head. When the engine is shut down for the night the coolant slowly accumulates in a chamber and upon start up it's burned in one large deposit.

The reason you don't see it while driving is because it's a slow leak and the amount of coolant entering the chambers is too small to detect. However, overnight, enough gathers to create white smoke when it's burned.

 

I was going to suggest worn rings...white smoke could also be oil...mine does that sometimes and I know it's oil because I can smell it. Typical on high mileage vehicles.

 

smoke or steam?

could simply be h2o condensing in a hot cat, pipe, or muffler and being blown out in the first few minutes of run time in the form of steam...

 

+1 There are mornings you would think my truck has a water cooled exhaust system, it spits water and condensation. In my case I blame it on my location and the weather.

 

I blow some white smoke at startup sometimes, also sometimes when I romp on it. I chalk it up to bad valve seals or worn rings. My motor has lots of miles on it. It's definitely oil, not coolant.

 

The smoke from poor oil control is bluish, nearly white. Oil smoke on startup is usually failed valve seals, and often with worn valve guides underneath -- the valve guide wear occurs because the seals have failed, and the oil that sneaks into the stem/guide interface bakes onto the stem making the stem thicker and sticky, causing wear.

I've seen this dozens of times. Tear down the head and you find carbon on the stems below the guides, sometimes more than a quarter inch thick. When they're that bad, the valve stem is usually stretched to go along with it -- the stem overheats due to the carbon blanket on it, and while overheated is stretched by the top of the carbon build-up banging into the bottom of the guide.

If it were mine, and a high mileage engine, I'd just replace all of the seals and check for any really wobbly valves while doing it. If none are loose enough to make me think it wise to pull the head and fix it, I'd then start saving my loose change for the rebuild that's coming. Not replacing the seals would mean the rebuild is required just that much sooner.

 

I'm thinking this is just normal condensation as the nights are getting cooler.