2010 Yukon XL Denali 6.2L - Occasional White Exhaust / Burns Oil - Causes?

[Mike L]

Our Yukon XL 6.2L engine (with about 150K miles) goes through 2 qts of oil every 4-6 weeks, and occasionally emits white exhaust. The strange things about our situation is:

• It hardly ever emits the white exhaust at home.
• It ONLY emits the white exhaust when my wife leaves work (at work) in the afternoon.
• it ONLY emits the white exhaust when the oil level is low (at the very bottom of the dipstick). Once I put 2 Qts of synthetic oil in the engine, the white exhaust completely stops until the oil level gets low again, typically 4-6 weeks later (I check the oil when I first see the white exhaust again).
• There are no signs of oil leakage on the pavement/parking spots.
  
• It does not emit the exhaust while driving, and not when running errands (repeated starting & stopping of the truck). Apparently, the truck must sit for several hours for it to occur.
• For what it's worth, the I had the rear main seal replaced about 10-15,000 miles ago.

At first, I thought it was the rings given the white exhaust. But if it was rings, it would smoke all the time. Ours doesn't. I'm not discounting rings, but I'm thinking it's unlikely that's the culprit.

What other causes might be behind the oil consumption & white exhaust?

Out of curiosity, how much should I expect to pay for a new replacement engine & installation? A rebuilt engine?

Should I be thinking of giving up the good fight on this truck and look at replacing the SUV altogether given these issues/mileage?

Thanks in advance!

 

[thompsoj22]

Ill guess valve stem seals. pull some plugs and see if the threads are wet and plugs fouled. if you do all of them keep them oriented per cylinder so you know which cylinders are burning oil. this test requires good valve cover gaskets. if they are leaking its a little harder to diagnose. In my exp wet threads are a symptom of the stem seal weeping the "pooled" oil that sits on top of them on engine shutdown. understand it is quite likely that your cats are degraded/bad as a by product of the soot from the burnt oil. good reman engine $3.500 plus R&R. stem seals are cheap and can be done in the vehicle without head removal but you have to be mechanically inclined. I have done it once on an inline 6 using nylon rope. Yup thats right "nylon rope" fed into the cylinder on a midstroke approaching TDC, you simply feed the rope into the cyl and than manually rotate the crank to use the rope to hold the valves closed. It works better than air! i know ill have nay sayers on that trick. the reason for nylon is it is clean and dosent induce any lint into the cyl. find out which cly's are burning oil first step! also is your driveway slanted or flat? check the PCV valve and plumbing.

 

[Mike L]

Ill guess valve stem seals. pull some plugs and see if the threads are wet and plugs fouled. if you do all of them keep them oriented per cylinder so you know which cylinders are burning oil. this test requires good valve cover gaskets. if they are leaking its a little harder to diagnose. In my exp wet threads are a symptom of the stem seal weeping the "pooled" oil that sits on top of them on engine shutdown. understand it is quite likely that your cats are degraded/bad as a by product of the soot from the burnt oil. good reman engine $3.500 plus R&R. stem seals are cheap and can be done in the vehicle without head removal but you have to be mechanically inclined. I have done it once on an inline 6 using nylon rope. Yup thats right "nylon rope" fed into the cylinder on a midstroke approaching TDC, you simply feed the rope into the cyl and than manually rotate the crank to use the rope to hold the valves closed. It works better than air! i know ill have nay sayers on that trick. the reason for nylon is it is clean and dosent induce any lint into the cyl. find out which cly's are burning oil first step! also is your driveway slanted or flat? check the PCV valve and plumbing.

Thanks for your comment. I’ll check the plugs. Interestingly, when parked at home, the truck is on a slight decline. When parked at my wife’s work, it sits on a slight incline (guessing 5 degrees on both the decline and incline).

 

[Fless]

Interestingly, when parked at home, the truck is on a slight decline. When parked at my wife’s work, it sits on a slight incline (guessing 5 degrees on both the decline and incline).

Have you tried parking it on an incline at home to see what it does after it sits a while like that?

 

[thompsoj22]

i would absolutely verify the pcv system is clear/unobstructed and functioning. also the PCV suction line is on the drivers side aft valve cover to intake manifold and the clean air inlet is passenger side valve cover to intake plenum. when the car is parked on an incline the oil that collects in the valve cover baffle area will gravity feed the pcv suction line you might just have a simple fix on your hands.