2012 Jetta TDi - smelling diesel inside cabin

[casm]

A couple of months ago, I picked up a 2012 Jetta TDi (Premium, no nav, DSG) sedan with approximately 22,500 miles on the clock. Roughly three thousand miles later, I'm noticing a faint smell of diesel inside the cabin at various times, and am at a loss as to what may be causing it. This is an intermittent issue, and I've been having difficulty pinning it down to any one potential cause.

The smell is not overwhelming, but it is noticeable and seems to be coming from the front. Both ambient (typically 60degF to 100degF) and engine temperature seem to have no effect as to whether it happens or not, and long vs. short trips don't seem to come into play either. There are no obvious fuel leaks that I've been able to spot, and no diesel has been spilled. I'm currently the sole driver of this vehicle, so I'm very familiar with how it has been used while in my ownership.

Fuel is overwhelmingly purchased at one of two stations (a Shell and a Chevron). This also does not seem to tie into things. No codes are being thrown or appear to be stored per the reader and app that I'm using (a no-name ELM327 bluetooth OBD-II dongle and Torque).

I should also point out that this is not my first diesel so I do have some familiarity with them, but it is my first modern (read: post-1989) one as well as my first diesel VW, so it's possible that there's something in all of this that I'm not aware of. Any ideas gratefully accepted.

 

[tjdeerslayer37]

Your car might be in regen when you're smelling the fuel. I never smelled fuel when mine did regens but it sure smelled funky. And my girlfriend couldnt handle that smell at all, she about barfed every time lol.

 

[mmn]

Sounds like a leaking seal at the DPF. I had the same issue smelling diesel exhaust in the cabin during regen. Went to the dealer, told them to specifically look for that and sure enough they found it. Should be no charge to replace if you're still under warranty.

 

[casm]

Your car might be in regen when you're smelling the fuel. I never smelled fuel when mine did regens but it sure smelled funky. And my girlfriend couldnt handle that smell at all, she about barfed every time lol.

Which is possible. I'm still getting used to having a modern diesel, but this is noticeable - more so than I'd expect. One possibility that was raised elsewhere was that diesel was tracked in. I'm not leaning towards this being particularly likely: I've removed the floormats (this car has the Monster Mats) and the issue remained persistent but still irregular. Having had the joy of an in-vehicle diesel spill before, I'm very much aware of how permanent the smell from that is - and given that this is intermittent, I'm not leaning towards a spill or tracked-in fuel. Possible, yes, but it just doesn't seem likely.

Sounds like a leaking seal at the DPF. I had the same issue smelling diesel exhaust in the cabin during regen. Went to the dealer, told them to specifically look for that and sure enough they found it. Should be no charge to replace if you're still under warranty.

Thanks for that; this was something I would not have known to consider. The car is definitely under warranty as this was a CPO purchase. I'll stick my head in at the dealer tomorrow and see about booking it in. I also really need to get up to speed with modern diesel technology. If anyone knows a good source to order an FSM from, please point me in that direction. Electronic copies are fine; part / ISBN numbers would be a huge help.

 

[jetlagmech]

the intake for the cabin air is at bottom of windsheild. You notice the window cleaner smell in cabin each time you wash the windows?? so a very small seap can get the smell in cabin but not have enough to notice a drip. common leak places is top of fuel filter housing and the intermediate pump just behind the filter. but the regen smell on my car is still noticeable though not as strong as it used to be.

 

[casm]

the intake for the cabin air is at bottom of windsheild. You notice the window cleaner smell in cabin each time you wash the windows?? so a very small seap can get the smell in cabin but not have enough to notice a drip.

Makes sense; thanks for that.

common leak places is top of fuel filter housing and the intermediate pump just behind the filter. but the regen smell on my car is still noticeable though not as strong as it used to be.

Good to know. I'll pass this on to the dealer next week when the car goes in.

 

[Matt927]

Diesel fuel or Diesel Exhaust?

Regardless, you should smell neither in the cabin.

 

[casm]

Diesel fuel or Diesel Exhaust?

I'd have to say it's a fuel smell, not exhaust.

Regardless, you should smell neither in the cabin.

Agreed. And it's becoming noticeable more often, and seems to parallel a decrease in fuel economy over the past 3-4 weeks. The fuel leak theory is looking good, but there could be other issues at play.

 

[azthegame]

There is a known issue with leaking fuel lines near engine. Pop engine cover off when you smell it and see if any fuel is pooling up by the injectors or on lines coming from pump to the left of the engine.

 

[tortega]

Diesel Smell in the Cabin

Today I stopped and re-fueled my 2012 TDI Sportswagon. After leaving the gas station we noticed later the smell of diesel fuel.
When I got home we looked under the hood and noticed some bubbles at the diesel fuel filter canister topside. I removed the 5 torx fasteners and looked around. I removed the rubber seal inside the canister and found the seal was separated and not providing the proper seal. I replaced the rubber seal and working well now...

 

[casm]

There is a known issue with leaking fuel lines near engine. Pop engine cover off when you smell it and see if any fuel is pooling up by the injectors or on lines coming from pump to the left of the engine.

Thanks for that. I've been trying to dig up specific info on this, but am failing. Got any links I can refer to?

Today I stopped and re-fueled my 2012 TDI Sportswagon. After leaving the gas station we noticed later the smell of diesel fuel.
When I got home we looked under the hood and noticed some bubbles at the diesel fuel filter canister topside. I removed the 5 torx fasteners and looked around. I removed the rubber seal inside the canister and found the seal was separated and not providing the proper seal. I replaced the rubber seal and working well now...

Interesting. Have any links to this one? I'm adding it to the list of things I'll be asking the dealer to specifically check when I take it in tomorrow morning.

 

[Matt927]

Remove the engine cover and poke around. I would focus heavily on the fuel supply/return lines, filter canister area and injector lines. As you already know, diesel stinks and the closer you get to the source the worse it will get.

Please let us know what the dealer finds.

 

[casm]

Remove the engine cover and poke around. I would focus heavily on the fuel supply/return lines, filter canister area and injector lines. As you already know, diesel stinks and the closer you get to the source the worse it will get.

This is going to be my next avenue of attack, because...

Please let us know what the dealer finds.

They found nothing. And while I was provided with a loaner and wasn't charged for the investigation, I'm not really happy about this for two reasons:

1) The car was returned to me with exactly one additional mile on the odometer. This means there wasn't much of a road test if any.

2) The issues persist.

It looks as though I really need to get an FSM for this thing; not thrilled with how the dealer evidently approached it. I may book it in elsewhere for a second opinion in the next week or two, but having described this to them as an issue that occurs while driving I would have expected to see signs of more road testing having been carried out.

 

[mmn]

I would see another dealer or mechanic, and have them get it out long enough to hopefully kick into regen. That is most often when the smell will show up, if it's not coming through at all times. It sounds like the did very little to look into the issue.

 

[TDI in MT]

How about the rubber hood seals? Are they in place? With 22k on it they probably are though.

 

[casm]

I would see another dealer or mechanic, and have them get it out long enough to hopefully kick into regen. That is most often when the smell will show up, if it's not coming through at all times.

That's the thing - if the car's going into regen, it's doing it on an incredibly regular basis. It's also something that is difficult to track given the weather here coupled with the distances normally driven. I am the first person to admit that this is my first ownership foray into a diesel made after about 1990, but given what I do know about how regen works and the smell that I'm experiencing, it just doesn't seem like that's the likely explanation - or, if it is, I'd like to know why it seems to be happening on a surprisingly regular basis.

It sounds like the did very little to look into the issue.

Agreed. The sheet that I got back from them when I collected it was unsurprisingly vague as to what was actually performed. My best guess is that they connected an OBD-II code reader, found nothing (which I told them they would, since I'd already done that), drove it around the block, and shrugged their shoulders.

How about the rubber hood seals? Are they in place? With 22k on it they probably are though.

Yep, everything in that regard looks solid. The car's at 26K, so it's still fairly factory-fresh.

 

[Locnar]

Try this link

http://forums.tdiclub.com/showthread.php?t=336996

I had this issue with both my 2012 AND 2013. Several others have as well.

It may not be the same issue because you seem to think it is a fuel smell...not exhaust. I originally thought it was fuel too...but after getting whiff after whiff, I went back to the dealer after being told the same thing as you.

Guess what? They both found and corrected the issue.

No fumes after they replaced the gasket / clamp.

Frustrating it happened again with the 2013...but at least it took no time to find an fix it. 30K miles later...all is well.

Anyway - good luck!

 

[casm]

http://forums.tdiclub.com/showthread.php?t=336996

I had this issue with both my 2012 AND 2013. Several others have as well.

It may not be the same issue because you seem to think it is a fuel smell...not exhaust. I originally thought it was fuel too...but after getting whiff after whiff, I went back to the dealer after being told the same thing as you.

Thanks for that; I'd somehow managed to miss it in amongst my searching. And I'll admit that I am fairly well convinced that it's a fuel smell and not exhaust - but I could be wrong. Hopefully I'll have some time this weekend to crawl under / over it and actually find something. It was doing it again today, and fuel economy's still in the mid- to high-20s range on average.

Guess what? They both found and corrected the issue.

No fumes after they replaced the gasket / clamp.

Frustrating it happened again with the 2013...but at least it took no time to find an fix it. 30K miles later...all is well.

Anyway - good luck!

The thread you linked above is definitely going to be used as a pointer for when it next goes in. I'm still very unhappy that it came back with virtually no discernible road testing having been done, so I'll likely book in with another dealer as well.

 

[Black_Smoke]

if the car's going into regen, it's doing it on an incredibly regular basis

I've done significant logging of regens on my car. The NOX regens to happen on a very regular basis especially if you are travelling under semi-constant conditions like cruising on the highway. My car regens for couple of minutes every 20 or so min when i'm on the highway.

When the car does a regen, it sends uncombusted hydrocarbons out of the engine, which react with the exhaust treatment components to chemically help with regeneration and create extra heat.

If you have an exhaust leak between the engine and the catalytic converter/dpf, you will likely smell fuel/exhaust during regen.

 

[casm]

I've done significant logging of regens on my car.

Interesting. Do you happen to know if this can this be pulled via OBD-II? I'm going on a 600-mile round trip tomorrow (back next week) and would love to be able to get some data on when regen is kicking in during that drive.

The NOX regens to happen on a very regular basis especially if you are travelling under semi-constant conditions like cruising on the highway. My car regens for couple of minutes every 20 or so min when i'm on the highway.

Good to know. FWIW, the smell is happening in city driving, on the highway, and in a mix of the two. There doesn't seem to be a pattern that I've been able to discern to when it happens - it just does.

When the car does a regen, it sends uncombusted hydrocarbons out of the engine, which react with the exhaust treatment components to chemically help with regeneration and create extra heat.

If you have an exhaust leak between the engine and the catalytic converter/dpf, you will likely smell fuel/exhaust during regen.

Understood. I'm starting to come around to the idea that my earlier suspicion that this was a smell of fuel may have been wrong and that it was actually exhaust, though it is more like a fuel smell than the exhaust smell I'm accustomed to from diesels. Then again, this is quite a bit different to every diesel I've ever owned, so it's a definite possibility. It'll be interesting to see how the car behaves during the trip. Worst case, I'll drop it in to the local dealer when I get there and have them take a shot at it.

 

[Matt927]

Do you see any exhaust staining towards the rear of the engine compartment on the heat shield material? Near the turbo area......

 

[Black_Smoke]

Interesting. Do you happen to know if this can this be pulled via OBD-II? I'm going on a 600-mile round trip tomorrow (back next week) and would love to be able to get some data on when regen is kicking in during that drive. Good to know. FWIW, the smell is happening in city driving, on the highway, and in a mix of the two. There doesn't seem to be a pattern that I've been able to discern to when it happens - it just does.

I am able to log my exhaust gas temperature using a cheap ELM327 bluetooth OBD thing and the Torque app on my android phone. If you have VCDS you can use that too. The regens are pretty un-mistakable by looking at the EGT's. Normal temp is around 425C. Temp during regen will be 750+C.

There are 3 temp sensors in the exhaust system. The temps you'll see on each will be cooler the further they are away from the engine.

It's also possible that you have a fuel leak at/near the tank. This is accessable underneath the back seat. It might not hurt to pull the seat up and have a look. SirSipsAbit has some under seat pictures that might be useful on this thread: http://forums.tdiclub.com/showthread.php?t=420664

 

[casm]

I am able to log my exhaust gas temperature using a cheap ELM327 bluetooth OBD thing and the Torque app on my android phone.

Awesome - this is exactly the setup I have.

If you have VCDS you can use that too. The regens are pretty un-mistakable by looking at the EGT's. Normal temp is around 425C. Temp during regen will be 750+C.

There are 3 temp sensors in the exhaust system. The temps you'll see on each will be cooler the further they are away from the engine.

Thank you for that; being able to put some numbers to this over time will be a huge help. Much appreciated!

It's also possible that you have a fuel leak at/near the tank. This is accessable underneath the back seat. It might not hurt to pull the seat up and have a look. SirSipsAbit has some under seat pictures that might be useful on this thread: http://forums.tdiclub.com/showthread.php?t=420664

It's a possibilty, and I'll take a look as soon as I have a chance.

 

[casm]

Summary: getting EGT numbers turned out to be largely unsuccessful, at least in the sense that they were obtained over the course of the entire 600-mile trip. Only about 100 miles' worth of data was captured, all of it on the way back today.

The graph of that trip is included below, but some quick explanations are necessary:

• GPS speed and OBD speed appear as having different values because GPS speed was set to MPH and OBD speed was evidently reported in Km/h. The curves match each other and the values are correct for their different measurement systems, so this disparity can be disregarded.
• EGTs seem to be holding steady at roughly 380-480degF at speed, with pronounced regen cycles at times. However, I note that regen seems to be very frequent and in some cases sustained for several minutes. EGTs are also going well below their usual numbers at the same sustained road speed at times, which doesn't make sense to me.

Anyway, here's the graph:

If anyone has anything to add to this, I'd certainly appreciate it. Sorry it's not the giant chunk of data I was hoping for, but it does at least give some idea of what's going on under mostly-sustained speeds.

 

[Black_Smoke]

EGTs are also going well below their usual numbers at the same sustained road speed at times, which doesn't make sense to me.

If you go down a hill or something, less (or no) fuel needs to be injected to maintain the vehicle speed. This causes the egt's to drop.

If you log your fuel consumption rate and EGT's you'll see this correlation.

 

[casm]

If you go down a hill or something, less (or no) fuel needs to be injected to maintain the vehicle speed. This causes the egt's to drop.

Which makes perfect sense. And correlating time of day on the graph with where I would have been at that time, this is the most likely explanation for the drop in EGTs. Thanks for the pointer.

If you log your fuel consumption rate and EGT's you'll see this correlation.

Fair point - but in daily driving, I have an overall elevation change of around 200 feet and it's spread out over the drive - basically, no sustained climbs or descents.

In any event, the diesel smell is still occasionally happening. Going to pop the hood tomorrow and see what I can see.

 

[Matt927]

Focus towards the rear of the engine compartment, turbo area. Look for any exhaust staining on the heat shield material.

For that raw diesel smell, focus on the fuel filter area. A small leak should be easily detectable with your nose.

 

[casm]

Focus towards the rear of the engine compartment, turbo area. Look for any exhaust staining on the heat shield material.

For that raw diesel smell, focus on the fuel filter area. A small leak should be easily detectable with your nose.

Looked, couldn't find a thing at either location; the closest I came was some light soot under the engine cover but not enough that I'd necessarily be concerned. At this point, I'm stumped. Any other ideas gratefully received.

 

[Matt927]

When you say engine cover, you mean the plastic sound deadening cover that snaps into place?

 

[casm]

When you say engine cover, you mean the plastic sound deadening cover that snaps into place?

Correct - the one over the top of the engine itself.