2007 Chevrolet Suburban with 160K miles, 5.3L V8. Has been drinking oil like you might drink bourbon...sipping it every day, and every once in a while you have to buy another bottle.

1. Blue smoke emanates from tailpipe after short distance driving. Or idling for a few minutes, shutting off, and returning the next day.

2. Blue smoke is NOT emitted upon heavy acceleration. Blue smoke is NOT emitted after driving more than 15 miles at interstate speeds, parking, and starting the next day.

3. The PCV hose between the intake runner resonator and a metal pipe below the oil filler neck had a large crack in the rubber fitting. Being below the engine decorative cover, this was not seen for months and months.

4. The PCV hose from the driver valve cover to the central port on the intake manifold is OK.

5. The driver valve cover has been replaced with the new baffle supposedly restricting the flow of oil vapor back to the intake.

6. The Displacement On Demand also called AFM V8-V4 control has been disabled to always run V8.

7. Many times before the PCV hose was replaced, the engine did not have any power, the transmission would not properly downshift, and the brake boost was minimal.

8. An engine oil cleaner by Liquimoly has been used. Drain oil was very black.

Could the cracked PCV hose explain symptom 7? I am not sure, because it has happened once after replacement, but also after idling for a short distance and parking for a couple of hours.

Do the symptoms point to valve guide seals needing replacement?

This message has been edited. Last edited by: 4MUL8R,

Take a look at this TSB:https://static.nhtsa.gov/odi/tsbs/2012/SB-10062524-7690.pdf

Valve seals and or guides are my suspicion.

The oil fill leak IIRC was a recall around 2011-2012. As for the oil loss I would guess that having the 5.3, you are losing it when your AFM is switching between 4 and 8 cylinders. Common. Our Suburban and Yukon with the 5.3 had the same problem. At the time, I didn't know why the Suburban was losing so much oil. After about 3 years of owning the Yukon, I started researching and found out the AFM was causing the problem. GMC in 2010 changed something in the 5.3 that helped with the oil consumption.

I think some of those years had piston replacement under warranty, my bet would be worn piston rings. Keep in mind that once those catalytic converters get hot they will burn off more oil and you not see as much smoke. Let it sit overnight and pull a couple spark plugs get a cheap borescope camera and see if there is oil coming down the valve guides and puddling on top of the piston, if you think it's valve seals.

Make sure the PCV valve is working (or replace), replace any leaking or suspect hoses, vacuum or oil breather related and any other simple stuff first.
Without proper vacuum any and all of those could happen.
Get a bottle of this engine purge stuff. Youu pour it in, let the engine idle for the specified time, then change the oil and filter. Sometimes this will free up stuck lower piston rings (oil ring). Didn't believe it until I saw it myself on other higher mileage cars.
May work, may not but it's worth a try. I like to start with the simple solutions first.

https://www.bgprod.com/catalog...ine/bg-engine-purge/

Throw some Lucas oil stabilizer in there next time you change the oil, or next time you add oil. Or use STP.

OP states the AFM is disabled.
OP states an additive cleaner was used.

Posters tell him it could be the AFM and to use an oil additive cleaner.

If members won’t even read the OP, how can any advice be worth a damn.

Working as a formulator I have some inside info on engine oils. I did increase the viscosity to 15w40 as a check on that concept. No benefit seen. The polymers used in the suggested products are not what I would want to add to my crankcase.

quote:

Originally posted by sigcrazy7:
OP states the AFM is disabled.
OP states an additive cleaner was used.

Posters tell him it could be the AFM and to use an oil additive cleaner.

If members won’t even read the OP, how can any advice be worth a damn.

I said nothing of using an additive cleaner, which is irrelevant.

I did suggest increasing oil viscosity, which will reduce oil entrance into the combustion through all paths. THINK! Then read.

Where's your contribution, by the way? Ripping into others for their input, when you don't bother to read and have nothing to offer, isn't really worth a damn now, is it?

Now having said that, use of an "oil cleaner" will often increase oil consumption. Go figure.

I would change the PCV valve first as it sounds like the cuplrit. There were issues with pistons with this engine which may be the cause, but doubtful. Usually with worn rings, you'll see heavy smoke on hard acceleration which you're not. WHat you're seeing sounds more like valves/valve guides as the source of leakage if it's not the pcv valve. I'd do a compression test and/or leak down test.

Are you running conventional oil or synthetic? How many miles does it take to go through a quart of oil? Those engines had a lot of oil leakage issues with synthetic oil even when they were new. Chevy changed the material of all of the various gaskets (oil pan, valve covers, etc.) due to that.

quote:

Originally posted by sns3guppy:

quote:

Originally posted by sigcrazy7:
OP states the AFM is disabled.
OP states an additive cleaner was used.

Posters tell him it could be the AFM and to use an oil additive cleaner.

If members won’t even read the OP, how can any advice be worth a damn.

I said nothing of using an additive cleaner, which is irrelevant.

I did suggest increasing oil viscosity, which will reduce oil entrance into the combustion through all paths. THINK! Then read.

Where's your contribution, by the way? Ripping into others for their input, when you don't bother to read and have nothing to offer, isn't really worth a damn now, is it?

Now having said that, use of an "oil cleaner" will often increase oil consumption. Go figure.

Calm down, Skippy. If you’d have read the thread, you’d know that neither of my objections were referencing your post. READ! Then think.

Giving advice without even bothering to read the OP is far worse than posting for the sake of posting. Maybe I should recommend that he check his tire pressure. Or maybe he should replace his cats. Yea, those are often problematic.

Here’s some real advice I’ll give the OP.

Look at these three things:

The PCV valve, the valve cover gaskets, and the valve seals, in that order. None of these items are expensive fixes.

Doesn’t sound like piston rings. The diag for rings is to go down a long hill with vacuum resistance. Mash the gas at the bottom of the hill, and if you get blue smoke, that’s rings. Smoke on startup is valve related.

As for why you don’t get smoke after freeway driving, I don’t know, perhaps to guess that it could be because the very hot engine cokes the leaking oil so it doesn’t produce smoke on the next startup.

There is no pcv valve.

The valve cover has already been replaced and has the new pcv baffle.

The valve cover gaskets are okay. No leaks.

The former owner used valvoline synthetic. I have used Mobil 1, until the last change. Here I filled with Shell Rotella T4 15w40. I am testing this detergent laden oil which has more solvency.

I like the theory that hot cats change vapor emission.

Start with a leak down test. That will tell you whether or not you have a big or small problem. That test is cheap as hell to find out what you're dealing with.

Question, if it were a valve issue is it conceivable that as the engine warms up and the metals in the head expand the issue may seem to go away or not be quite as obvious?

quote:

Originally posted by stickman428:
Question, if it were a valve issue is it conceivable that as the engine warms up and the metals in the head expand the issue may seem to go away or not be quite as obvious?

Yes.

OP- #7 symptoms would usually generated by a vaccuum leak somewhere.

On a flat road accelerate hard then take your foot off the gas while someone watches you go by. If there’s smoke while you’re on the gas it’s rings. If it smokes when you let off the gas it’s valves.

quote:

Originally posted by 4MUL8R:

Do the symptoms point to valve guide seals needing replacement?

Does it smoke when you start it, then stop? That's the usual sign of that in my experience.

Yes, the smoke is upon starting the engine. It then stops. This does not occur unless the drive is short distance. Fifteen miles or more, no smoke.

No, it does not smoke when I accelerate briskly.

Sorry, didn't catch that you had the AFM disabled when I first read your post. How long has it been disabled? I recently disabled mine at 96,000 miles.
Rotella T, I've never put diesel oil in my gas trucks. Is this to flush out contaminants in a one time change? Good luck,.