Burnt oil smell occasionally?

[SmoothSonic]

Don't these cars have a charcoal vapor trap in the factory airbox? It's possible that they aren't good enough to stop the smells.

Also, you guys noticing this through the vents, what condition are your cabin air filters in? Is it still noticable with the a/c on recirc mode?

Just curious as on my 1.4 with no cat I don't get any strange smells of any sort from the engine, and as a mechanic i'm more sensitive to them than normal. The A/C does smell funny to me but it's a plasticy, resin type of smell from something in the vent work that may just be because the car is only a couple months old.

Well, my car's mileage has only reached 2,817 miles on the odometer (3-months old). I started to notice this when my car was only at around 1,500 miles. I'd think my cabin air filter would still be in good shape at that point. I have my air set on recirc mode when this problem happens and usually when the heater is running, since it's still cold outside at night. I haven't tried it with the cold a/c on.
It doesn't seem that it's the a/c system because I smell the odor on the exterior as well as on the interior.

I'm not a certified mechanic and I've never smelled this before in any car that I've owned. It sort of has an exhaust type of odor to it and it saturates my clothes. I don't know what crankcase vapor is supposed to smell like, but from reading this forum I am learning about it.

Right, normally crankcase venting is burned back through the running engine, but with the car off and temps still high enough to create some hot air with oil vapors in it, it has nothing pulling it into the engine and could be wafting out of the air intake tract.

So, if this were the case, what mechanism do other cars generally have to prevent the wafting of vapors?


I suppose I could hook up an UltraGauge and monitor the conditions at which this problem occurs in an effort to see if it's possible to control the events that lead up to the symptoms. Maybe the data I gather could be beneficial to everyone in this forum.

 

[Italianjoe1]

I'd have to look at this PCV system in detail but it's possible that it's returning vapor before the air filter and getting out into the engine bay that way. I know some OEM's like that route, so the oil vapors hit the engine air filter and get cleaned up, but it contaminates the air filters very quickly. This would be fixable by moving the hose connection to a spot further along the intake tract if that is the case.

Also with the high temperatures these engines run it doesn't help to not boil the oil off. We are parking a car that is allowed to run at 220+ degrees at the sensor, which means that there are places in the engine well over 250 degrees at shutdown and they heatsoak much hotter when the cooling oil and coolant stop moving. This could easily get into the mid 300 range where you can start to boil off certain parts of the oil mixture. A poorly thought out/recirculated PCV system then allows that smell to get out of the engine system. Just thinking out loud.


It's also likely that even on re-circ mode the heater is pulling some fresh air in and that's why you still notice it. The A/C systems on newer cars will only do some of what you ask at certain settings, for simplicity sake they just let it stay displaying what you ask for until it can reach that level.

 

[SuperFudd]

Interesting.
I wonder what the EPA would say about this.
Do Cruze owners have this problem?

 

[SmoothSonic]

I went for a long drive to a friend's home last night. The outside temperature was comfortable and there was no need to run the heater. I showed him my car and decided to open the hood to take a peek since he hadn't seen my car yet. While looking under the hood, I told him about the odor. He described the current odor as being from plastic. Now, my nose is confused.

 

[Papasonic]

I went for a long drive to a friend's home last night. The outside temperature was comfortable and there was no need to run the heater. I showed him my car and decided to open the hood to take a peek since he hadn't seen my car yet. While looking under the hood, I told him about the odor. He described the current odor as being from plastic. Now, my nose is confused.

The odor that I've described is definitely crankcase fumes, or blow-by gasses: I can say this because of experience working on older vehicles that used to emit these vapors profusely because of worn internal components. Vehicles in the 1950's had a road draft tube that vented the crankcase vapors to atmosphere down and under the engine. An engine that was well worn would constantly emit a cloud of vapor from this vent tube all the time that it was running. Now the modern ventilation systems recirculate these vapors back into the intake system to be burned during the combustion process. I believe the reason we sometimes smell these crankcase fumes is that under certain conditions, the crankcase ventilation system is pressurized beyond design limits, and the excess pressure has to vent somewhere; that somewhere is to atmosphere where we smell these odors. The problem seems more specific to the 1.4 turbo engine, as its ventilation system is a bit more complex than the naturally aspirated 1.8 engine. I doubt that this issue will ever be resolved completely, and probably won't affect the operation, durability, and longevity of the engine. It just plain stinks!

 

[SmoothSonic]

I just want to write an update since my last posting. I am nearing an end to the following Winter season since my last report. My car has reached over 16,000 miles and I have been using my heater since the temperatures are below freezing. I am not experiencing those odors that I had at around 2,000 miles. The engine smells clean now. So, I think my friend might have been right about the plastic odors. Maybe there's a break-in period for the new plastics to release their vapors on a hot engine.

 

[ChrisJ]

I have never smelled anything from my Sonic, but very often I get damn near poisoned by diesel truck fumes.

For some reason, the Sonic seems to vacuum these up more than any other car I've had. In the summer I run recirculate most of the time so it's never a problem but in the winter I can't due to fogging up issues, so often I get stuck behind a truck and it's awful.

 

[pabst_tom]

why yes

Interesting.
I wonder what the EPA would say about this.
Do Cruze owners have this problem?

There is a smell in the Cruze cabin. I told the dealer it smells like the coolant. So what did they do. Charged me to clean the a/c box in the car and change the filter. Nice. They also noticed no smell, so then how did they know to clean the a/c box thingy?

Wife's Cruze also has the notorious rattle behind the instrument cluster. I just don't want to pay $90+/hr to find nothing. I tell my wife to turn up the radio to hide it. Wouldn't buy another Cruze, but another Sonic - yes.

We are a Chevy family.

 

[shorebreeze]

In very cold weather I get a gassy smell on startup and for the first few minutes of driving. Noticed this a couple of weeks ago in Minnesota with routine 10 to 15 below zero lows and highs barely making it above zero. Have not noticed it in Chicago with lows around zero and highs in the teens and 20s (for non-US readers these numbers are degrees Fahrenheit). The effect is as if I'd been careless in a gas station and walked through slush with gasoline in it and climbed in the car without rinsing my boots.

 

[Frizodanizzo]

I've noticed lately I never really noticed it before if it was doing it or not. I get a puff of blue smoke the minute the car turns over and goes to running. After literally that fraction of a second it's gone. I've had my girlfriend give it a little gas nothing, drive behind the sonic in her car no smoke. Would this be from some oil seeping into the intake while running and settling till it starts and blows it out again? Maybe a catch can might not be a bad idea. If that would remedy it where do you find one?

 

[Frizodanizzo]

In very cold weather I get a gassy smell on startup and for the first few minutes of driving. Noticed this a couple of weeks ago in Minnesota with routine 10 to 15 below zero lows and highs barely making it above zero. Have not noticed it in Chicago with lows around zero and highs in the teens and 20s (for non-US readers these numbers are degrees Fahrenheit). The effect is as if I'd been careless in a gas station and walked through slush with gasoline in it and climbed in the car without rinsing my boots.

I started getting a really super gassy smell right before that disc burst on the valve cover when it did I stopped smelling it and it never came back after it was replaced

 

[JesusTheAgnostic]

Check the check valve in the intake manifold. Take off the hose on top of the manifold that's pretty much on the center of it. Towards the injectors not towards the back. Then just shine a light in and check for a little orange ball. If it's not there then that's why you're burning oil.