Just bought a 2009 H/C/I Z06 with 18k miles to replace a 2008 that I had. Has a FAST intake, a fancy polished throttle body that I don't recognize, kooks 2 inch, and a haltech. And it has some strange oil issues that are baffling me.

With my 2008 you would wait 5 to 20 minutes to pull the dipstick and it would read properly.

With the 2009 you have about a minute and a half to check the oil or it will not read on the dipstick at all. Not 5, not 20. After 2 minutes it will not show on the dipstick at all.

So, after draining it and putting the correct amount of oil in it started to smoke. And by smoke I mean huge clouds of thick oily blue smoke coming out of the pipes that blotted out the sun and caused both the polar ice caps to melt. Until it sucked down a quart of oil. Once it was ~about quart low and the oil in the pipes burned out it completely stopped smoking, and so I drove it about 2k miles. It use not a drop as far as I could tell. I changed the the oil again and the same thing happened. Huge clouds of smoke until it used about a quart, then it completely stopped.

I say about a quart because it's still almost impossible to confidently and accurately check the oil.

I also noticed the PCV lines have a lot of oil in them. I checked the routing on all of them, including the one for the oil tank bump out. All filled with oil, but I can't find one that might be plugged. They are routed properly.

At this point I'm baffled. I have no idea why it drains back the oil into the pan almost immediately. And no idea why it's really unhappy unless it is a quart low. I would rather not keep running it a quart or more low. And worse, all the oil it sucks up and burns when the level is correct just has to be hurting this engine. And why does it stop smoking and using oil once it reaches about a quart low?

I'm not sure where to look next. Any ideas?

 

 

 

Yes, both plugs were removed, thanks.

The way it empties the oil back out of the tank so quickly is by far the biggest concern as it makes it really difficult to check that the system has the proper amount of oil in it. It "seems" to stop blowing out oil once it is a quart low, but that is hard to confirm as it is really difficult to check the oil level when it is draining back out of the tank as fast as it is.

It's also a real concern starting this thing after it has been sitting more than 5 minutes knowing that there is probably no oil in the tank, it's all in the engine sitting where it doesn't belong.

 

It is my understanding that you are supposed to check the oil a very specific way on the Z06. When I do my oil changes I do as the service manual says. Run the car until operating temp then shut down and after 5 to 10 minutes you check it. I usually wait until oil temp is at least 170 before I shut it off. Also the oil will drain down to the pan. That's why you dont check the oil when cold.

 

Also could it be possible that someone somewhere installed a 2006-2008 oil tank in the car for whatever reason? Capacity would be 8 quarts instead of 10.5. Just a thought. You never know what kind of crap you could buy from someone.

 

Fully aware of that, thank you. However this car is draining back into the tank almost immediately. If you wait the 5 minutes it will show no oil in the tank. This is half of the problem. If you check it at one minute it will already show a quart low. 10 seconds after that, almost 2 quarts low. By a minute and a half to 2 minutes it will not even show oil on the stick anymore.

I thought of that too, but it has the correct tank. The 2009 and up has the plastic top half, and the add-on extra tank mounted on the side, with the second vent line running up from the top of the add-on, teed into the air vent. This has the correct tank.

And yet, if the tank is filled with the correct capacity the car will pass it all through to the exhaust until it is about quart low. "about" because actually checking the oil is pretty much a guessing game.

I'm sure the two issues are related but I am unable to determine what the root cause is.

I do have a 2008 tank on hand, and thought of swapping it, but I don't know if it will mount.

 

Are you draining the sump lines when you drain the oil? There's still oil in the lines, which could explain why you're throwing oil into the intake, that's getting burned out of the exhaust.

As far as the oil draining back right away, I don't know. Maybe a check valve on the pump or in the tank is bad?

 

I'm not seeing a check valve on the tank or the oil lines. Is there one that is replaceable?

 

when I get home I will look at my service manuals and see what I see.

 

 

Thought I'd circle back here. Just did cam, lifters, pushrods, springs, balancer, radiator, fans, oil cooler, etc. With that I also swapped the oil pump from the gm unit to a new Katech blue. The issue has gone away. Now I have the normal wait 5 to 15 minutes and check it. The tank is no longer empty within 2 minutes of shutting off the engine. I can't think of anything else that I might have touched which would change the oil drain back behaviour except maybe possibly the oil pump. I still just don't have a solid answer, but it isn't a problem anymore.

 

oops, I forgot.... the "blowing oil out the exhaust until the tank is low" issue was found to be that it was pulling oil out of the tank vent line that goes to the intake, ahead of the throttle body, under high vacuum. I put a catch can in that line which has prevented it from pulling more oil into the engine. Being able to check the oil level properly now will probably be the ultimate cure. I'm betting that the tank was actually over full when it has happened.

 

Thanks for keeping us up to date, too many of these problem threads never reveal what the fix was. Glad you got it taken care of.