I have a 2004 Silverado 1500 4x4 with a 5.3L and 150,000 miles. Exhaust is blowing blue smoke on start up that tells me that its probably oil. smoke seems to trail off after it has been started for a few minutes. I took it to a dealership to have them check out the engine and they said they found oil in the intake manifold. He also mentioned that the knocking sound that my engine makes could be a lifter (not sure what that is or does).

First he started talking about replacing the valve cover which I figured would probably be accurate...then a little later he started talking engine swap which to me sounds kind of extreme. So i figured I would post here on the forums to see what the experts thought. Any Ideas?

 

If it were me, I locate the "knock". If it is a lifter, your in luck. Have them pull the valve cover that the lifter is located, and the intake manifold. Replace the lifter, reinstall the intake and valve cover with new gaskets. Some of the older 5.3 vortec had issues with plastic intake gaskets and the red coolent didn't like each other (dexcool).

 

Or head going

 

I thought head at first too, but wouldn't there be coolant loss as well. and either some oil in the coolant or coolant in the oil.

 

and thank you for the reply kevinkpk, I'm going to be taking from the dealer over to a local mechanic my dad does bussiness with and have him give me a second opinion. hes saying most likely lifter and valve seals as well.

 

Sticking to that guess bro lol good luck

 

Looking at your symptoms there may be more than one cause for this problem. It includes valve cover, engine piston ring. But as you said that valve cover looks fine then I would like to say that check the piston ring. No need to go for engine swapping.

 

so my mechanic pulled the valve cover and there was tons of sludge in there. saild that the bearings for the rocker arm were all worn out which was causing the knocking...he's doing a full teardown now to see if anything else is worn or shot so i'll update once i have more info.

 

So just to give some resolution to my problem, I ended up replacing the engine. Put one in with 67k on it....and less then 100 miles later it broke down...took it back to the mechanic and they sent him an engine with 41k on it...he took the valve covers off and it was caked with peanut butter looking sludge like the first engine so we sent that back and finally after about a month of not having my truck we finally got a good engine with 70k on it.

new problem....now my a/c wont blow through the vents, just the defrost like its stuck there. I have no idea how to troubleshoot this. it blows cold so i know its not a problem with the compressor...havent tried to put heat through so i'm not sure what to do at this point. any ideas.

 

These things have a safety default that sends air to the defrost. I don't know if thats your problem, but you might pull the glove box, and look around under the dash for the blend doors ect.