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Blue Smoke Duriing Start Up.

tmicklet

By tmicklet
in Ask A GM Technician

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tmicklet Enthusiast

tmicklet

Posted
Posted

Hello,

 

I have a 2004 GMC crewcab with the 5.3L and 87000Kms( mostly highway). Recently (last two weeks) I began to noticed blue smoke when I started the truck. It always smokes during a cold start, sometimes a couple of hours after driving it will smoke on a re-start. The truck has had all regular maintenance and oil changes. I have installed a magnaflow exhaust and volant cai.

 

The PCV in not serviceale in my truck, apparently its built into the valve cover. I was able to determine that air is flowing through the pcv tube. It is not blocked.

 

My next guess is the valve guides/seals, but this seems unlikely due to the time frame and mileage. That and I have never heard of a 5.3 having this problem. I have cold started the truck and then shut it off quickly and pulled all the spark plugs and found them all to be wet with oil. Not soaked but not a nice white/brown colour either.

 

Could anyone suggest another possible cause and/or personal experience with a problem like this?? What could be allowing oil into all cylinders and can fail quickly? Is there something in the intake that can possible cause this? I am thinking something common to all cylinders? I just cant see all the seals wearing at the same time. Any info or suggestions are welcome, thank you for your time.

99xjsport06 Enthusiast

99xjsport06

Posted
Posted

We've got a 2003 Silverado with the 5.3L that smokes when cranked up cold after sitting facing up hill. Been doing this for approx. 35,000 Miles (truck has 115,000 miles on it now). It burns about 3-4 quarts per 3,000 mile oil change.

 

Does it seem to do it worse when parked up hill, like on ours? The truck is usually backed into our driveway, which has it facing slightly down hill, so it's not really noticeable most mornings.

jefferias Enthusiast

jefferias

Posted
Posted

i work in a head shop and id honestly say the valve stem seals worn prolly, could be bagged out guides as well though. hard to tell without tearing apart lol

SKYrado03 Enthusiast

SKYrado03

Posted
Posted

I would have to go with the majority on this, valve guides/seals.

 

It would be a one in a million, but your truck's heads could of slipped past quality control.

Have you ever noticed tappet noise?

One of the keys that lock the valve stem, may have broke/slipped allowing enough movement to let the oil slide by.

 

But like, jefferias said, hard to tell without tearing apart.

tmicklet Enthusiast

tmicklet

Posted
  • Author
Posted
I would have to go with the majority on this, valve guides/seals.

 

It would be a one in a million, but your truck's heads could of slipped past quality control.

Have you ever noticed tappet noise?

One of the keys that lock the valve stem, may have broke/slipped allowing enough movement to let the oil slide by.

 

But like, jefferias said, hard to tell without tearing apart.

 

Hey thanks everyone for your input.

 

I appreciate the quick response. I have not noticed any valvetrain noise as of yet. Could you explain what you said about the keys that lock the valve stem? Is there a drawing somewhere of these parts? Any info regarding your theory regarding the keys would be appreciated. It may help me determine my next step.

 

Regarding the other post I also park the truck facing downhill but I notice the smoke either way. If you find out something please let me know.

 

Thanks again.

jefferias Enthusiast

jefferias

Posted
Posted
I would have to go with the majority on this, valve guides/seals.

 

It would be a one in a million, but your truck's heads could of slipped past quality control.

Have you ever noticed tappet noise?

One of the keys that lock the valve stem, may have broke/slipped allowing enough movement to let the oil slide by.

 

But like, jefferias said, hard to tell without tearing apart.

 

Hey thanks everyone for your input.

 

I appreciate the quick response. I have not noticed any valvetrain noise as of yet. Could you explain what you said about the keys that lock the valve stem? Is there a drawing somewhere of these parts? Any info regarding your theory regarding the keys would be appreciated. It may help me determine my next step.

 

Regarding the other post I also park the truck facing downhill but I notice the smoke either way. If you find out something please let me know.

 

Thanks again.

 

 

 

im pretty confident its not your valve stem keepers. they either work or dont and youd know if you lost one cause the valve would fall into the combustion chamber and wammmm NO GOOD. the keepers just have a groove or set of grooves that fit into the valve grooves and they are held on by spring pressure

tmicklet Enthusiast

tmicklet

Posted
  • Author
Posted

Thanks for the info jefferias, I had a blonde momment. I was thinking when the other guy said valve keys that there was some wicked cool technology that I had never heard of. I agree with you though the keepers must be ok because there has not been any large whammmo. Its still running great. Noticed the dex-cool was low the other day, maybe another piece of the puzzle? It is going to the dealership tuesday. Cheers

  • 2 weeks later...
tmicklet Enthusiast

tmicklet

Posted
  • Author
Posted

Just an update,

 

I took the truck into the dealer, they said valve seals and wanted to rip the heads off to change them. I have since done a few things but mainly changed the oil and replaced it with GM 5w-30. Its been a couple of weeks and the smoking is pretty much all gone. I cant believe it, but knock on wood, no huge plumes of blue smoke. The only thing that I can think of is possible the GM oil has an additive to lubricate and swell the valve seals. In any case what ever it is, its working. Thanks everyone for your input. Cheers

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