2019 CX-5 Signature(Turbo) Burning Smell in cabin

[mac.mc78]

Freaked out Canadian customer here with a 2019 Signature 2.5T that is around 95,000km.

Recently, when starting the car for the first time in the morning and while the car is idling to warm up, Ive been smelling a burning smell in the cabin. Initially it seemed to only be when the car was warming up, but now I can smell it intermittently even while driving. Its not sweet smelling, and it smells more like oil/rubber to me. It initially comes on strong during the first 30-90 seconds of the car being on, and then the smell subsides and only occasionally will I catch a whiff of it.

There are no visible signs of oil leaks - nothing on the ground etc. I don't seem to see the oil level getting lower, and the coolant is fine and so is the brake fluid. All visually inspected to ensure they're at normal levels. Confirmed by both the dealership and myself.

I took it to mazda a week before the extended (mazda added protection) plan wore out, and they couldn't find anything leaking at all. I specifically asked them to check the cylinder head issue, and they claimed the car was perfectly fine - no leaking anywhere. Dealership claimed they coudln't smell it but I suspect thats because I had already driven the car for quite a while before getting it to them. The smell really only is there when I initially start the car up for the first time in the day but I can smell whiffs of it occasionally thru a drive.

Does anyone have any advice? Is there a specific place I SHOULD be looking? IF so, any diagrams or pictures would be great - I'm an IT guy, not a car guy so if yiou just say check x, I may have difficulty finding it.

Im particularly concerned because in Canada we don't have the extended warranty that mazda provided for the cracked cylinder head issue that the US has, and my purchased extended warranty is now 2 weeks overdue. The dealership claimed because I at least had it in writng that I was smelling burning that if anything goes wrong I shoudl be fine but I find that very hard to believe.

 

[N7turbo]

You were right to investigate the potential for a cylinder head crack. However, that would cause a coolant leak, not an oil leak.

You could check for an oil seep at the turbo oil feed banjo bolt or line:

• Look down behind the engine from the passenger side.
• Check the banjo bolt, feed line, and the heat shield directly below.

You could also check for a valve cover gasket leak:

• The rear of the valve cover sits directly above the exhaust manifold.
• A small seep will bake off on the turbo heat shield during warm‑up.

There is also the possibility of the smell coming from the PCV, but I would think that would be continuous and not just within the first few minutes of driving.

Finally, if you had an oil change done recently, it's possible that someone spilled oil somewhere.

 

[22323]

You were right to investigate the potential for a cylinder head crack. However, that would cause a coolant leak, not an oil leak.

You could check for an oil seep at the turbo oil feed banjo bolt or line:

• Look down behind the engine from the passenger side.
• Check the banjo bolt, feed line, and the heat shield directly below.

You could also check for a valve cover gasket leak:

• The rear of the valve cover sits directly above the exhaust manifold.
• A small seep will bake off on the turbo heat shield during warm‑up.

There is also the possibility of the smell coming from the PCV, but I would think that would be continuous and not just within the first few minutes of driving.

Finally, if you had an oil change done recently, it's possible that someone spilled oil somewhere.

It would be a home run if it's because of oil spilled recently - but smelling it right after start up?

 

[Lazy2.5]

Most likely, you are smelling fumes from the cold start.

Since idling for longer than 30 seconds is detrimental and explicitly not recommended in the owner manual, it's the perfect scenario for creating massive amounts of exhaust smell, emissions, and wear on the engine - idling on a rich fuel mixture, when cold, and not in gear. Once the idle settles down, just take off.

When was the last time you changed the oil? My car is fairly stinky on a cold start if the oil is dirty, but the smell clears up significantly after changing the oil, and i never smell anything when the engine is warm. only the exhaust, though that could be strong enough to permeate into the cabin in the first few min of driving, especially noticeable when coming to a stop. that's likely what you're experiencing. but, I do not have my second cat, and i'm at nearly 350k km.

if you are experiencing fuel dilution that's significant enough, your oil level will rise due to fuel in the oil, masking potential oil burning. (and, you are experiencing elevated levels of fuel dilution if you "warm up" the engine by idling it.)

Assuming that there are no leaks or oil consumption, theoretically, there should not be any issue.


start the engine when cold. stand outside the car. is the smell coming from the exhaust? if yes, that's "normal." after driving for at least 20 minutes, get out again. if the exhaust still smells, then you got a problem.

if you never rev the engine past 3000rpm, you could be experiencing a strong smell due to deposits in the engine and cat converter. in this case, go ahead and go full throttle in second or third gear once or twice to about 5000rpm or so, and then notice a strong smell, this is "good", you have cleared out deposits which should help.

 

[N7turbo]

Most likely, you are smelling fumes from the cold start.

That smells like burning gasoline. The OP is describing a burning oil or rubber smell.

 

[mac.mc78]

Most likely, you are smelling fumes from the cold start.

Since idling for longer than 30 seconds is detrimental and explicitly not recommended in the owner manual, it's the perfect scenario for creating massive amounts of exhaust smell, emissions, and wear on the engine - idling on a rich fuel mixture, when cold, and not in gear. Once the idle settles down, just take off.

When was the last time you changed the oil? My car is fairly stinky on a cold start if the oil is dirty, but the smell clears up significantly after changing the oil, and i never smell anything when the engine is warm. only the exhaust, though that could be strong enough to permeate into the cabin in the first few min of driving, especially noticeable when coming to a stop. that's likely what you're experiencing. but, I do not have my second cat, and i'm at nearly 350k km.

if you are experiencing fuel dilution that's significant enough, your oil level will rise due to fuel in the oil, masking potential oil burning. (and, you are experiencing elevated levels of fuel dilution if you "warm up" the engine by idling it.)

Assuming that there are no leaks or oil consumption, theoretically, there should not be any issue.


start the engine when cold. stand outside the car. is the smell coming from the exhaust? if yes, that's "normal." after driving for at least 20 minutes, get out again. if the exhaust still smells, then you got a problem.

if you never rev the engine past 3000rpm, you could be experiencing a strong smell due to deposits in the engine and cat converter. in this case, go ahead and go full throttle in second or third gear once or twice to about 5000rpm or so, and then notice a strong smell, this is "good", you have cleared out deposits which should help.

Its definitely not cold-start exhaust smell.

This is something that has started new recently on a 7 year old car.

I rarely let the car idle too long once it hits 1000rpm, but I do live in a cold climate that requires the car to warm up a little longer especially in the winter.

This is definitely some kind of fluid or rubber burning smell.

The smell comes from the cabin air vents, not from outside or anywhere else.

 

[Lazy2.5]

Its definitely not cold-start exhaust smell.

This is something that has started new recently on a 7 year old car.

I rarely let the car idle too long once it hits 1000rpm, but I do live in a cold climate that requires the car to warm up a little longer especially in the winter.

This is definitely some kind of fluid or rubber burning smell.

The smell comes from the cabin air vents, not from outside or anywhere else.

Yes, I figured this is something abnormal.

There is a distinction between warm-up and circulation, when idling. You will never get the engine oil or transmission fluid up to temp by simply idling it.

Circulating the fluid, which is what you're actually doing, on the other hand is good and useful. But thats done after 30 seconds, even when it is cold outside.

The only way to actually warm up the car is to drive it.

 

[madar]

Maybe check your exhaust for anything stuck to it. Years ago a plastic shopping bag got tangled on the pipe before the catalytic converter, the thing melted on and burned a little at a time each time the engine started. It was on there for weeks before I had to go under and scrape it off but that thing stank, burning plastic residue.

 

[mac.mc78]

I’ve added some pictures today. The only thing I can see is in front of the oil fill cap and to the left there appears to be some darker debris there (lots of sand in this area) and on the right it’s completely just sandy/white colour. The smell is definitely coming from this side of the engine from what I can see.
Can anyone with a trained eye see anything I should be going back to Mazda about?

 

[Lazy2.5]

I think you need a valve cover gasket. Hard to tell from the pics.

 

[mac.mc78]

I think you need a valve cover gasket. Hard to tell from the pics.

Is there a way I can take a better picture to show you that would be more indicative?

 

[Silly Wabbit]

Remove and under panels and look from underneath

 

[Lazy2.5]

Is there a way I can take a better picture to show you that would be more indicative?

Need to see a clear pic where the cylinder head mounts to the engine Block.

 

[Jmaz]

I think you need a valve cover gasket. Hard to tell from the pics.

I think the engine and surrounding compartment needs a good bath.

 

[Lazy2.5]

Yea, I agree. Lol

 

[gtbigup]

This