Fly By Night

I bought an '06 Sierra 2 months ago, 118k miles on the L33. It has been burning oil to the tune of 1qt in 700 miles. I did some looking online and learned about the PCV issues, pulled the valve cover, tested the baffle for leaks and it checked out, the valve cover, rocker ect have more carmley colored crust on them then I would expect. Next I removed the Tb and there was no more then an ounce of oil in the intake. At this point I'm thinking either rings or guides, I pulled plugs to see if some where worse then others, they all were the same tan color, I ran a compression test and got between 152 and 158 psi on all cylinders at 6,500'. I don't think it's valve guides because I don't try he smoke on a cold start. Power and mpg are good, it isn't using coolant not is there oil in it and it doesn't leak. Does anyone have any idea where it's going? I wish I did a wet compression test to get a better idea of what kind of shape the rings are in.

SAPPER

iTrader: (10)

Rings. I work at a dealer and we see this all the time. We'll re-ring it and no issues.
FYI, We do pistons, rings, new rod bearings, new rod bolts and of course all the supporting parts.
We had a guy here that could pull the motor, new pistons/rings, have it back in and running in 6 to 7 hrs.

RixTrix

If it was mine I would put a catch can on the PCV and test, before I tore it down.
& check both sides of the PCV (vent and valve).

Is this motor getting flogged? Heavy towing? Or GrandMa'd?
Has someone tried (unrealistic) extended service intervals?
Fuel pressure checked? MAF cleaned?

Fly By Night

Thanks SAPPER, is there anything else to check before yanking it to pieces?

Do you know why the rings go? I was under the impression it was almost impossible to kill these motors in under 200k miles. Will a wet compression test give me an indication of their shape?

Fly By Night

Do you mean both sides of the valve cover?

Since I've had it its been pretty easy driving, a few WOT runs, I towed a boat a couple hundred miles over rolling terrain, nothing too extreme. The P.O. seemed pretty mellow but he also said he did oil changes at 3k miles which I have a real hard time believing based on the junk in the valve covers, so I have no idea how it was treated all its life.

I have not checked fuel pressure, I looked at the MAF bulb and it looked fine, I have not cleaned it. How do do you think either of these could be related to oil consumption?

Darth_V8r

iTrader: (4)

Just asking but do you know if the heads were ported. Seen oil get past the rocker bolts all the time on ported heads. 700 miles per qt is high but thought I'd suggest it

Fly By Night

I don't know but the truck is otherwise bone stock so I doubt that would have been the first mod.

Fly By Night

The oil in there is what the PO left in it, he says it is 5w30 Valvoline Synthetic, would switching brands or viscosities maybe change my oil burning issue?

I don't get how it can burn so much oil and not see any smoke or have any residue on the plugs.

kingtal0n

iTrader: (1)

Use an air compressor to pressure test the crankcase, use about 1-2psi of pressure max and find any leaks.

Else, a leakdown test may help confirm the rings. But even if it is the rings, that just means that pressure is creeping into the crankcase, which the pressure test I suggested above will simulate to some extent. And if that is truly the cause, then the PCV route/plumbing is undoubtedly involved( that is how oil makes its way from the crankcase to the throttle body) . You may simply be able to 'catch can' that oil until ready to get inside the engine.

Fly By Night

Add pressure to the crank case through the pcv hole?

There is hardly any oil in the intake, as far as I can tell all of the runners leave from the top of the main plentum, so if quarts of oil were getting into the engine by way of the intake there would have to be much more oil in there, Gm Says up to half a quart can live in the intake with pcv issues, I have no more then an ounce.

RockinWs6

Another thing to consider at that mileage is PASTED OIL CONTROL RINGS.

Fly By Night

What do you mean pasted? I'm not firmiliar with that term and a quick Google search didn't net me anything.

RockinWs6

Carbon builds up around the rings and renders them useless.

kingtal0n

iTrader: (1)

You can add pressure anywhere there is a hole into the crank case i.e. oil fill cap, anything on the crankcase side of the pcv valve, or even to the fresh air inlet (air filter tract) with a blocked air filter. At this moment you should be realizing that atmospheric pressure gets into the crankcase via the air filter tract, so any pressure attempt you create in the crankcase is going to be "leaking" from the air filter and must be accounted for or eliminated. That means a pressure drop behind the filter will apply a suction to the crankcase and pull oil into the intake tract.

The oil cap is connected to the oil pan, the whole crank case is a solid single unit and it routed to the air filter tract as a source of fresh air, but can also be a pressure relief when the rings start to leak compression. You add pressure to simulate 'bad piston rings' but without the oil whipping/frenzy of the spinning moving components, so instead of oil you will likely get a flow of air, just like in a boost leak test. If any of the engine's oil seals are poor you could hear it in that instant.

Fly By Night

My machinist also suggested this, he said to try valvoline high mileage in 10w30 to see if the thicker oil will slow things down/ high detergents clean off the oil control rings, what do I have to loose? I'm also going to try some sea foam in the oil before I change it and in the intake to see if anything frees up.

RockinWs6

If I were you I'd stay FAR FAR away from seafoam........... don't say I didn't warn you. I would try GUNK engine flush AND FOLLOW THE INSTRUCTIONS! Also you could try some ATF in the engine oil, 1/2 qt at every oil change. A good combustion camber cleaner will help too. Unfortunately those dam oil ring packs are hard to clean up. That's why when the dealer changes everything they don't use oil anymore because the oil control rings are clean ....for a while......

rpturbo

iTrader: (47)

I wouldn't flush a engine at this point, period. I have seen far more harm, than good come from this on a engine that is having issues already.

If you have tore down many LS engines, you know the rings get carbon all over them, and are a major cause of oil consumption. I have seen guys pull them, and just clean them, and put them back together with all the same parts, and once cleaned, they are fine. Would I do it.......I don't know. I guess it depends on the miles, and how the bearings look like.

RockinWs6

I use ATF regularly without any issues and I used the gunk engine flush many many times. It safe as long as you follow the instructions. Really best way to clean the rings is good top engine cleaner product and use diesel grade engine oils.

Fly By Night

What do you recomend along the lines of a good top end cleaner?

RockinWs6

If you can find the GM or the Mopar top engine cleaners either one is fine. There are plently of others out there too. The important thing is know how to use it so it gets down into those nasty azz pasted oil control rings. I would probably let it soak for a few hrs after fogging the engine with them. Just be careful not to over do it, just put in enough at a time to slow the engine. Once you think the cylinders are good and coated have someone else shut it off and let it sit for 3-4 hrs.