Chevy 5.3 V-8 best guess diagnosis

[greenbush future]

My Chevy Avalanche 2008 with 110K on her has been maintained to the tee from new. Oil changes (non synthetic) every 3K, tranny flushes all the basic maintenance has been done as they where needed. What I'm getting now is a puff of oil smoke when cold starting, and even then it's only maybe every 5th or 6th start. It clears up quick and appears to just be what may have dripped into the combustion chamber from sitting. Doesn't burn oil on regular basis at all, only when I cold start and like I said, it's done and gone after 3-5 seconds of running.
I'm guessing I have bad valve seats, which are allowing some oil in. I haven't run a compression check yet, to see if it's rings, but because she doesn't burn oil on a regular basis, I'm thinking that shouldn't be the issue.
Anyone have any ideas I might try to get this thing back to perfect? I planned on driving this thing for another 100K but need to address this. What do you guys think the issue is?

 

[bruceb58]

Re: Chevy 5.3 V-8 best guess diagnosis

Worn valve guides/seals not seats. I wouldn't worry about it until you are ready to pull the heads at some point. You could try replacing the valve stem seals but if the valve guides are worn, even new seals won't help.

Edit: Found this informative thread on another blog site:
http://www.gm-trucks.com/forums/topic/93751-2005-chevy-silverado/
Probably should check your PCV system too.

 

[greenbush future]

Re: Chevy 5.3 V-8 best guess diagnosis

Worn valve guides/seals not seats. I wouldn't worry about it until you are ready to pull the heads at some point. You could try replacing the valve stem seals but if the valve guides are worn, even new seals won't help.

Edit: Found this informative thread on another blog site:
2005 Chevy Silverado - Ask the GM Technician - GM-Trucks.com
Probably should check your PCV system too.

PVC would be an easy fix. I don't think it has ever been replaced on this 5.3 that I know of. Sure beats new valve seals seats guides.
Thanks much Bruce

 

[bruceb58]

Re: Chevy 5.3 V-8 best guess diagnosis

I have same engine. Going to look at mine as well. I don't have your issue.

 

[briangcc]

Re: Chevy 5.3 V-8 best guess diagnosis

My '04 GMC Sierra 1500 SLE 5.3L started out the same way - little puff of smoke on startup and would quickly disappear. That's how it started. Then it turned into a smoke screen the US Marines would be proud of. Mechanic I took it to said "Valve Seals". I think the quote I had was between $500-800 for them to do it. Never had it done, turned it in on a Tundra.

And I was religious on my oil changes too - every 3k with oil, filter and STP oil treatment.

 

[robert graham]

Re: Chevy 5.3 V-8 best guess diagnosis

When I change my oil I pull the PCV valve out and rinse it with carb cleaner so that little spring-loaded plunger/valve inside is moving freely....these valves last forever as long as you keep them clean and free. You can check your valve stem seals by pulling each spark plug and check for deposits from burning oil.....My 5.7 LT-1 has 180,000 miles on it and a couple of plugs show deposits....I just pull them out and sand-blast them...lot easier and cheaper than replacing those seals....at least for now/until it gets a lot worse or I trade/sell the car....Get somebody to drive behind you and check your tailpipe for smoke while slowing down or speeding up....It may well be your PCV system rather than valve seals....

 

[robert graham]

Re: Chevy 5.3 V-8 best guess diagnosis

My '04 GMC Sierra 1500 SLE 5.3L started out the same way - little puff of smoke on startup and would quickly disappear. That's how it started. Then it turned into a smoke screen the US Marines would be proud of. Mechanic I took it to said "Valve Seals". I think the quote I had was between $500-800 for them to do it. Never had it done, turned it in on a Tundra.

And I was religious on my oil changes too - every 3k with oil, filter and STP oil treatment.

If your oil return passages were sludged up it could have caused the oil to puddle under the valve covers and cause that smoking past the seals....I think Toyota has been known for that....

 

[bruceb58]

Re: Chevy 5.3 V-8 best guess diagnosis

If your oil return passages were sludged up it could have caused the oil to puddle under the valve covers and cause that smoking past the seals....I think Toyota has been known for that....

That would have to be a lot of sludge! You realize that Brian was talking about the Chevy engine and not Toyota right?

 

[robert graham]

Re: Chevy 5.3 V-8 best guess diagnosis

That would have to be a lot of sludge! You realize that Brian was talking about the Chevy engine and not Toyota right?

My mistake on the engines, but sludged return passages can cause puddling around valve seals and oil burning....

 

[Fun Times]

Re: Chevy 5.3 V-8 best guess diagnosis

If it continues to smoke after replacing your PCV then you may need the new style valve cover as GM had a service bulletin about close to the same problem your experiencing.

http://www.justanswer.com/gmc/5semx-gm-2008-gmc-sierra-sle1-5-3l-vortex-engine.html

By the way, if you have the active fuel management system, there is a small oil filter under the oil pressure sender that you may want to change about every 50K to avoid hydraulic roller lifters damage.

The filter is item number 452,
http://www.performanceboats.com/pb-...variable-displacement-gm-v8s.html#post1265805

 

[JustJason]

Re: Chevy 5.3 V-8 best guess diagnosis

If it's just a "puff" and it clears up before the engine actually warms up. It's probably just 110k miles worth of crap and normal oil burnage and all the other hydro carbon crap sitting in the catalytic converter and the rest of the exhaust. You can pull the plugs and look at them to see if the engine is burning oil or not. And of course check your dipstick. But small puffs here and there I would not worry about. You could spend weeks chasing ghosts on that. If you had bad valve seals, you would be loosing oil. If you had a clogged crank breather, you would be burning oil like crazy, hot or cold. That converter is like a giant exhaust filter that catches everything. I would personally just keep an eye on the oil level, and as long as your not loosing much over the course of 3 to 5k miles, not worry about it.

 

[Volphin]

Re: Chevy 5.3 V-8 best guess diagnosis

Hi Greenbush, I'm a Master Tech and I've pop in with my .02

Valve guides are not the culprit on this engine. You have changed the oil regularly, so they should not be an issue until 200-220K mi.
Valve seals can cause the issue you are having, but it would be regularly smoking on startup and you would notice oil loss between service intervals.

YES there is a VC update AND PCV update for your symptom exactly. I'd go that route first as another poster suggested.

Another question is whether this truck has AFM (Active Fuel Management). This disables some cyls until needed. I'd get a tuner and set it to disable AFM. Many have had issues with this system...

 

[dolluper]

Re: Chevy 5.3 V-8 best guess diagnosis

Next oil change replace one quart/litre of oil with trannie fuild and then the next oil cnange do the same.....this will soften up the oil seals......add some brake fuild also if you want ....the properties in these fuilds have softening agents

 

[greenbush future]

Re: Chevy 5.3 V-8 best guess diagnosis

Hi Greenbush, I'm a Master Tech and I've pop in with my .02

Valve guides are not the culprit on this engine. You have changed the oil regularly, so they should not be an issue until 200-220K mi.
Valve seals can cause the issue you are having, but it would be regularly smoking on start-up and you would notice oil loss between service intervals.

YES there is a VC update AND PCV update for your symptom exactly. I'd go that route first as another poster suggested.

Another question is whether this truck has AFM (Active Fuel Management). This disables some cyls until needed. I'd get a tuner and set it to disable AFM. Many have had issues with this system...

Well the AMF has already puked and been repaired on this 5.3 under warranty at 45K. and I do lose about 1 quart of oil on my 3k oil changes, just not through huge plume's upon starting cold. The truck has always used a quart in between. It's the oil puff that is new, and it doesn't happen every cold start, but seems to happen more often of late. Maybe every 4-or 5th start. I'll do the PCV change out, I just need to locate the darn thing, then replace. Thanks much for chiming in and sharing what you know.
One more ? with this 5.3 being already fixed for the AFM system, would you still disable it? I don't seem to get any better mileage than 5.3's w/o this technology. I average 14.8 city maybe 18 highway driving. Thanks again for all your information Volphin!!

 

[agallant80]

Re: Chevy 5.3 V-8 best guess diagnosis

My 2007 had bad valve seals. It took a few hours to replace but was not bad.

You are going to need one of these
KD Tools - 2078 - Valve Spring Compressors - Part#: 2078 - Rakuten.com Shopping

and one of these
http://www.summitracing.com/parts/mor-62385?seid=srese1&gclid=CK_96_a0vb0CFUuXOgodiBQA-A

Its really not that bad.

 

[greenbush future]

Re: Chevy 5.3 V-8 best guess diagnosis

My 2007 had bad valve seals. It took a few hours to replace but was not bad.

You are going to need one of these
KD Tools - 2078 - Valve Spring Compressors - Part#: 2078 - Rakuten.com Shopping

and one of these
http://www.summitracing.com/parts/mor-62385?seid=srese1&gclid=CK_96_a0vb0CFUuXOgodiBQA-A

Its really not that bad.

It looks like this will need to be done to rid the smoke, I'll replace the PVC first, but I'm still betting this IS the real issue.

Thanks much for sharing. It's almost warm enough in Michigan to do this job and freeze.

 

[dolluper]

Re: Chevy 5.3 V-8 best guess diagnosis

Usually the puff at start up is valve guides or seals.......extreme is head oil drains plugged up.....thats the reason to try trannie fuild first

 

[Volphin]

Re: Chevy 5.3 V-8 best guess diagnosis

Well the AMF has already puked and been repaired on this 5.3 under warranty at 45K. and I do lose about 1 quart of oil on my 3k oil changes, just not through huge plume's upon starting cold. The truck has always used a quart in between. It's the oil puff that is new, and it doesn't happen every cold start, but seems to happen more often of late. Maybe every 4-or 5th start. I'll do the PCV change out, I just need to locate the darn thing, then replace. Thanks much for chiming in and sharing what you know.
One more ? with this 5.3 being already fixed for the AFM system, would you still disable it? I don't seem to get any better mileage than 5.3's w/o this technology. I average 14.8 city maybe 18 highway driving. Thanks again for all your information Volphin!!

I'd disable it if it was my truck. If you use a programmer you can always turn it back on.
1 Qt every 3K is A LOT of oil loss. Not leaking any from the sending unit are you? Hows the compression?
Rule of thumb used to be that if you are burning 1 qt every 3K then it's time for a rebuild.
If you were driving a Mopar 5.9L, I'd say you have an intake plenum leak...

BTW, other posters have suggested adding trans fluid to your oil. Trans fluid is just basic hydraulic fluid with added detergents. There is no "softening" agents in the fluid at all. In fact, trans seals get brittle and hard over time just like other oil immersed seals. There is no benefit to adding some to the crankcase at all, however, there IS the risk of thinner oil films on the engine bearings. Not advisable.

 

[dolluper]

Re: Chevy 5.3 V-8 best guess diagnosis

Hum Lanolin
Modern ATF typically contains a wide variety of chemical compounds intended to provide the required properties of a particular ATF specification. Most ATFs contain some combination of additives that improve lubricating qualities,[1][2][3] such as anti-wear additives, rust and corrosion inhibitors, detergents, dispersants and surfactants (which protect and clean metal surfaces); kinematic viscosity and viscosity index improvers and modifiers, seal swell additives and agents (which extend the rotational speed range and temperature range of the additives' application); anti-foam additives and anti-oxidation compounds to inhibit oxidation and "boil-off"[4] (which extends the life of the additives' application); cold-flow improvers, high-temperature thickeners, gasket conditioners, pour point depressant and petroleum dye. All ATFs contain friction modifiers, except for those ATFs specified for some Ford transmissions and the John Deere J-21A specification;

 

[greenbush future]

Re: Chevy 5.3 V-8 best guess diagnosis

I'd disable it if it was my truck. If you use a programmer you can always turn it back on.
1 Qt every 3K is A LOT of oil loss. Not leaking any from the sending unit are you? Hows the compression?
Rule of thumb used to be that if you are burning 1 qt every 3K then it's time for a rebuild.
If you were driving a Mopar 5.9L, I'd say you have an intake plenum leak...

BTW, other posters have suggested adding trans fluid to your oil. Trans fluid is just basic hydraulic fluid with added detergents. There is no "softening" agents in the fluid at all. In fact, trans seals get brittle and hard over time just like other oil immersed seals. There is no benefit to adding some to the crankcase at all, however, there IS the risk of thinner oil films on the engine bearings. Not advisable.

No leaks in anything, the engine is spotless. This truck has used about 1 quart per change from new. And from what I've read, it's rather common with the 5.3, but what do I know? I wouldn't add trans fluid to the crank case, so that's just not an option. The AFM does nothing of value so turning it off, not a bad idea. I still need to do the compression check, but really don't get any on-going smoke out the tail except at random cold starts. That's the goofy part, it's like one out of 5 starts that gives me the smoke, and usually after it's when it's sat overnight, or all day at work. I"ll report back the compression #'s when I do the job, I appreciate everyone's input.