6.0 vortex burning/consuming oil issue

[dfPuffer]

Hello all, Looking for some help trying to find out what may be causing my oil consumption issues. any direction would be appreciated.

My 2003 Yukon Denali 6.0 (209,000mi) had the rear main seal replaced about 10,000 miles ago because of leakage. I ran it awhile prior to the new seal. keeping an eye the oil level. I ran it down pretty low a couple times to the point where it barely read on the dipstick.. didn't use any specific oil brand as long as I kept it on the dipstick. Prior to seal change I had no oil usage issues. since the change I have been going thru a quart every 1300 mi on highway and 700 in town.

I have no coolant in my oil or oil in coolant. The only oil I see is my cover gasket seeps minor oil...nothing even close to what I am using. no smoke out the exhaust on startup, hammering it down cold or hot. my oil pressure is 35-50psi depending on temp and rpms and I get 12-18 mpg. it runs great just a slight rough idle if you feel for it.

Since seal change 5 months ago I have done the following on order

-cleaned the PVC valve (light oil in it...no spring type) been there since I bought truck at 60,000mi

-Compression test- all cylinders dry 180-190 w/oil 182-200. seems high...but consistent. first timer with new cheap gauge and 8 cranks.

-new plugs & wires. some oil fouling but not gross. gonna try to match up pics of plugs I took back then with cylinders today

-replaced original catalytic converter on left side only (p420 code)

-changed intake gasket. felt slight stumble when sprayed carb cleaner around area. (knock sensor clean area between gaskets not oily) cleaned throttle body-all vac lines to it, fuel injectors, intake and path down to valve as best as I could with carb cleaner. had some caked on carbon/oil outside injector spray path . looks lot better now.

just don't know where to look next. valve seals, gunked up rings, bad rings? could the main seal change gone wrong...that the timeframe it started....any ideas besides my engine on its way out.

 

[Rand]

how much is it using?

 

[EvanD]

any smoke on acceleration?

drips?

 

[dfPuffer]

quart every 600-700mi in town...1300 on the highway.

 

[ls1mike]

Your Vortec is really LS based nothing Vortec about it.

So you can try the following. Seafoam treatment, they are known for building up carbon which can cause oil to get by the rings.
Get a real oil catch can setup, it helps.

The intake is dry but changing the gasket most likely helped drivability, didn't help your oil consumption.

What weight oil are you running? What type?

 

[1kickbuttranger]

Originally Posted By: dfPuffer

My 2003 Yukon Denali 6.0 (209,000mi) had the rear main seal replaced about 10,000 miles ago because of leakage. I ran it awhile prior to the new seal. keeping an eye the oil level. I ran it down pretty low a couple times to the point where it barely read on the dipstick.. didn't use any specific oil brand as long as I kept it on the dipstick. Prior to seal change I had no oil usage issues. since the change I have been going thru a quart every 1300 mi on highway and 700 in town.




Sounds like you were using oil before the rear main. I wouldn't think that much would leak past the rear main. 209K is some good miles.

 

[ls1mike]

At that many miles it won't hurt to throw something a little bit heavier in there.

 

[dave1251]

Try some 15W40.

 

[dfPuffer]

Originally Posted By: EvanD
any smoke on acceleration?

drips?


No smoke at all even when I hammer it down on the highway. If you look hard the tail pipe on startup in the morning you can barley see a tiny bit of smoke for 10 seconds for about a foot out and that's it.

No drips just my cover gaskets are seeping some oil. its a very tiny amount.

Originally Posted By: ls1mike
Your Vortec is really LS based nothing Vortec about it.

So you can try the following. Seafoam treatment, they are known for building up carbon which can cause oil to get by the rings.
Get a real oil catch can setup, it helps.

The intake is dry but changing the gasket most likely helped drivability, didn't help your oil consumption.

What weight oil are you running? What type?


Seafoam this weekend. I did the intake gasket cuz I was spraying carb cleaner and noticed a stumble in my idle when I hit that area...new gasket gone now.

Using Mobile super 5000 5w30. During my self changing time when the main seal was leaking I had no preference.

Originally Posted By: ls1mike
At that many miles it won't hurt to throw something a little bit heavier in there.


Im tempted to but I like to try to find the source first then switch up to thicker or high mileage oil.


I only got Sundays to work on it, so this weekend im going to do a leak down test to see where any air escapes as well as a cover gasket change...and go from there. hopefully the worst is the valve seals. probably do a Seafoam treatment too. I really do appreciate the feedback here. cant afford the high labor cost and I get to try new things and buy new cool tools.

 

[dfPuffer]

Been a couple weeks and finally got a chance to look at my truck. I decided to change the valve seals. Opened up the valve cover and it looked varnished up inside. Not sure what 210k miles buildup should look like.

Wasn't sure how much psi I should use to hold the valves up. I set the regulator to 40psi. I ran into a problem when I hooked up the air to the cylinder my little 3 gal compressor gave me about 7-8 min before it lost too much pressure to do the job. Good thing I tested to see how long the cylinder could hold pressure before I pulled the spring just to see the valve to fall. Decided to stop till morning before I even start. I heard the air escaping from the valve seals but more from the oil filler tube. Doesn't sound good. I had good numbers on previous compression test. I guess I could have good compression but bad rings. Not sure what to do at this point.

Do the seals quick at a lower pressure to give me more time... 30 lbs maybe and run an oil additive to try to clean rings not big on additives but I think that’s all I can do before a new motor as this one fails. Any help would be greatly appreciated.

 

[Oro_O]

There are some specific cars well known to coke up the oil control ring then cause lots of oil burning. Never see the oil when running, and just a puff on start up. Compression test will be totally healthy of course so that won't reveal it. Many Saturns, newer I4 toyotas, and 1998-2000 Isuzu troopers do this badly. I don't know for certain it's your rings, but I imagine there's a oil type and usage combination that can cause it on many other vehicles. Here's how I cured mine (1st post is mine):

Oil for ring issues

It cannot hurt to try and doesn't cost much (besides down-time letting it soak and 1/2 a can of Seafoam). Running HDEO 15w-40 or a high-end synthetic like Pennz. PP/UP or M1HM can also clean them up I am told. I am switching to that my next OC now that I have things under control.

 

[Tzu]

Does your truck have GM's infamous cold start piston slap? Maybe a piston soak overnight with MMO or upper engine cleaner through the spark plug holes in hopes it might be sticky rings from excessive carbon buildup.

I've heard of a redesigned PCV valve that was to help with oil usage too, so that could be an option. I would think you would get more oil loss on the highway with rpms up instead of in town? My old Toyota burns more oil on the thruway than city driving. I would try PYB 10w30 and see if that helps too being a little thicker. The 15w40 seems like the last resort oil if it were me.