Blue smoke on cold start and excessive oil consumption 2005 Tahoe

[Tahoe97]

We just completed a round trip drive between NC and FL running 10 straight hours in both directions at 75mph+ in our 2005 Tahoe (5.3L) . We have 270,000+ miles on the engine and it still runs great but historically uses more oil than normal. No oil leaks anywhere. Before the 1st 700 mile drive, I topped off the oil but had to add 1 qt upon arrival. Same deal on the return. Used 1 qt in 700 miles.

After the trip we started seeing blue smoke coming from the exhaust upon the 1st start of the day. We had not previously seen this after any long trips so this is a new development. After the 1st start of the day, any subsequent starts during the day do not produce the smoke. It has also not been as bad as the picture below which was the 1st start on the day after the 700 mile return drive. It has become less severe with each day but still remains to some degree.

I am seeing some online discussions that suggest the drivers side valve cover with the built in PCV valve is problematic on long extended drives with the original design allowing oil to get through the PCV valve system and into the combustion chamber. Is this in fact a possible cause?

The dealer suggested we may have a stuck ring and actually recommended putting 1 qt transmission fluid into the oil to clean out any carbon buildup in the cylinders and then after about 400 miles change out the oil again. Does this make sense or is this not wise?

Any and all recommendations are welcome. Thanks!

 

[wjburken]

To answer your question about putting transmission fluid in your oil, it is not unheard of to put a quart of it in as the mechanic suggested.

Might try and put a catch can in between your valve cover and your intake to catch any oil that may be getting pulled through there.

 

[PNWYukon]

Read over here: https://bobistheoilguy.com/forums/threads/gm-ls-engine-3rd-revision-valve-cover-install.251305/

 

[Mudsport96]

The Silverado that I got from the father in law did something similar. After sitting overnight it would burp a blue cloud on start up, but not on consecutive starts that day. So hit the local pull-a-part and snagged a valve cover from a 99 to 02 truck, cleaned it good and put it on with a new pcv valve from an 01. It took a couple weeks to clear up, because I assume there was residual oil in the intake manifold. But that was 3 years ago, I now have the truck and my daughter drives it with virtually no smoke on startup. You can smell a hint of it, but at 400k miles what can you expect? I'm sure at this point the valve guides are worn pretty good lol.
I also did this mod on my 06 Tahoe after seeing the results on the Silverado. Figured I'd just get out ahead of the issue.

 

[Tahoe97]

Read over here: https://bobistheoilguy.com/forums/threads/gm-ls-engine-3rd-revision-valve-cover-install.251305/

Thanks! That is consistent with what I am hearing as the fix. Hopefully I can get that taken care of this week.

 

[Scottydoggs]

thats going to be dead valve seals with those miles.

what you say its doing is exactly what bad seal do.

you could fix it your self, if your ok with taking the rockers and springs off, then you can replace the seals. hell id do new springs while your in that deep too.

 

[89Suburban]

thats going to be dead valve seals with those miles.

what you say its doing is exactly what bad seal do.

you could fix it your self, if your ok with taking the rockers and springs off, then you can replace the seals. hell id do new springs while your in that deep too.

Yeah same thing a guy I work with with the same truck needs new valve seals. His is like twice as bad as that. I told him about the catch can but it didn't make a difference. He is putting new valve seals in it soon.

 

[Scottydoggs]

Yeah same thing a guy I work with with the same truck needs new valve seals. His is like twice as bad as that. I told him about the catch can but it didn't make a difference. He is putting new valve seals in it soon.

catch cans not even a band aid for bad seals. oil leaks down the valve stems either drops into the cylinder if its open or lays on the valve once fired up its a oil bath in the cylinders.

ive done em on my old car. but i only did em cause i was doing rockers and new springs, kinda silly to not change em on a 220 k mile engine while you can easily change em.

best to use a compressor to fill the cylinders to keep the valves from dropping, but you can also use rope, feed it in the plug hole then turn the engine over by hand till you feel it not turning. now the rope is pushing up on both valves and you can take the springs off.

 

[89Suburban]

catch cans not even a band aid for bad seals. oil leaks down the valve stems either drops into the cylinder if its open or lays on the valve once fired up its a oil bath in the cylinders.

ive done em on my old car. but i only did em cause i was doing rockers and new springs, kinda silly to not change em on a 220 k mile engine while you can easily change em.

best to use a compressor to fill the cylinders to keep the valves from dropping, but you can also use rope, feed it in the plug hole then turn the engine over by hand till you feel it not turning. now the rope is pushing up on both valves and you can take the springs off.

Yup, cloth rope right? Not nylon to scratch the cylinders.

 

[Scottydoggs]

dont think it really matters, but i have head of ppl using shoe laces, you know them 80's fat wide ones like run DMC wore lol

 

[mattbta]

best to use a compressor to fill the cylinders to keep the valves from dropping, but you can also use rope, feed it in the plug hole then turn the engine over by hand till you feel it not turning. now the rope is pushing up on both valves and you can take the springs off.

I was using my dad's old farm air compressor to hold the valves up doing a spring job on my '99 Trans Am while swapping cams back in the day. Compressor failed (and spit oil everywhere) and valve dropped.

 

[Scottydoggs]

I was using my dad's old farm air compressor to hold the valves up doing a spring job on my '99 Trans Am while swapping cams back in the day. Compressor failed (and spit oil everywhere) and valve dropped.

damn that really sucks.

 

[2007 Denali XL]

Is there any blue smoke during general driving or only at cold start up?

 

[Tahoe97]

Replaced the left side valve cover (built in PCV valve) as recommended with the updated design-valve cover GM Part # 12570427. Pictures of the old valve cover shown here. Quite a bit of buildup at the drain openings which probably allowed oil mist to move through the PCV valve. We'll see if this rectifies the situation. Thanks for the tips everyone.

 

[Tahoe97]

Is there any blue smoke during general driving or only at cold start up?

only at start up

 

[OR VietVet]

While the updated valve cover can't hurt, I agree with @Scottydoggs and @89Suburban say. At that mileage the seals are likely the cause of the blue smoke at start up. The longer you sit after shutting off the engine, the more smoke you see. If I was really doing it right I would pull the heads and do valve guides as well and surface the heads and do new head bolts and gaskets. The easier patch is just doing the seals.

 

[Tahoe97]

So far no blue smoke from the tail pipe at start up or anytime thereafter. Can the forum members assisting me with this post help me find the correct AC/Delco part number for the hose that comes out of the PCV valve and feeds over and into the top of the engine? This is a 5.3L 2005 Tahoe, VIN #1GNEC13T25J209032. I know for sure AC/Delco part # 12582227 is not the correct one. I thought I would replace that line now that I have a clean valve cover and clean PCV valve. I can only imagine the residue in that line which is the reason I thought I would put on a new one. Thanks for the help!

 

[Scottydoggs]

So far no blue smoke from the tail pipe at start up or anytime thereafter. Can the forum members assisting me with this post help me find the correct AC/Delco part number for the hose that comes out of the PCV valve and feeds over and into the top of the engine? This is a 5.3L 2005 Tahoe, VIN #1GNEC13T25J209032. I know for sure AC/Delco part # 12582227 is not the correct one. I thought I would replace that line now that I have a clean valve cover and clean PCV valve. I can only imagine the residue in that line which is the reason I thought I would put on a new one. Thanks for the help!

View attachment 261860

id re use that line, why spend money needlessly. if you think its caked up spray it out with brake cleaner. or just put a catch can between them two ports.

 

[OR VietVet]

I bet this is it: https://www.rockauto.com/en/moreinfo.php?pk=10356744&jsn=1766&jsn=1766

Is at RA.

 

[dougo]

I would first try a Seafoam or Marvel mystery oil treatment in both the gas tank and oil follow the instructions for the amount for the crankcase the gas tank i would is 1 oz per gallon of the Seafoam you might be surprised Never use trans fluid for cleaning.