Exhaust Fumes in Car: Causes & Solutions

Hello fellow enthusiasts,

"Ever since I got my Passat, there's a strong smell of exhaust fumes inside the car when the sunroof is open (usually starting around 50-60 km/h). It's especially noticeable (as you might expect) when I'm driving uphill quickly under load."

The problem is that, due to the negative pressure inside the cabin (hello Bernoulli's principle), air is "sucked in" through all the cracks. It seems that the smell of diesel exhaust is somehow seeping in through somewhere near the trunk door (it's a station wagon!). My exhaust system is completely sealed along its entire length .

Could it be that the rubber seal on the trunk door is leaking? Or are there other possible causes?

Thank you in advance.

As you know, I had the same model. In my case, there were no issues. It's probably the seal in the...

Hm, which Passat model do you have?

Normally, the problem is usually caused by the seal on the tailgate, either because the seal itself is damaged or because the tailgate doesn't fit properly in the lock.

Hello,

@Julian: is a 35i.

@Joerg: The paint job actually looks good and is undamaged.

So, either it's a poorly sealing lock or the gasket itself. Can you replace it yourself? You would definitely need a good adhesive for that .

Okay, so I'm not specifically familiar with the 35i model, but the seal is usually always inserted into the fold of the metal.
Remove the old seal, clean the groove, apply a thin layer of soap or silicone oil to the inside of the new seal so that it slides easily over the groove, and then it's finished.

Hmm, so I don't know the 35i specifically, but the seal is usually always inserted into the groove of the metal.
Remove the old seal, clean the groove, lightly lubricate the new seal with soap or silicone oil on the inside so that it slides easily over the groove, and then it's done.

'I would see it that way too. I once did something similar on my dad's gasoline meter. It wasn't a big deal; it just took a little time, and then it was done.'

Okay, I thought these seals were glued in. Well, I'll go get one of those parts then (hopefully this is the cause of the problem).

My poem makes a rather soft impression (labrig), but it still looks good. In fact, there's really only one way it could be. I wouldn't know of any other entry points .

I wouldn't know of any other entry points .

Well, forced ventilation might also be an option depending on the situation, and the pre-filters sometimes need replacing. Could you please check (by removing the bumper) whether they close tightly and whether the rubber flaps feel elastic.

Julian wrote:

Well, forced ventilation might also be an option depending on the situation, and the pre-rotators sometimes too. Could you please check (by removing the bumper) whether they close tightly and whether the rubber lamellae leave an elastic impression.

aha, I've learned something again. At which point does the airflow enter the interior space with this defect ? Then you could just seal it up .

Normally, air only escapes from there if you have the ventilation on or close the doors. However, these rubber flaps can be damaged by rodents or wear and tear, and sometimes exhaust fumes can also enter through them. It depends on the location of these ventilation grilles.

"That sounds logical. I just don't have any idea where they are located. Surely, you should be able to see them from inside the car. Everything seems sealed up under the rear panels."

However, I've discovered something else: In the area of the door lock, the seal has a 3mm gap at the connection point (between the beginning and end of the seal). Since the exhaust system on the 35i is so strangely designed (the outlet is under the bumper), it's possible that this is where the unpleasant smell is coming from. I'm going to try sealing it and report back.

'But I also experienced that crack.'
The forced ventilation is located on the sides at the rear, underneath the bumper. So, remove the interior trim panels, then there's a floor panel in my case, remove that, and then you'll see the 'things.'

joergs wrote:

The forced ventilation is located on the sides at the rear, under the bumper. So, remove the cover from the inside, then there was a floor panel in my case, remove that, and then you'll see the "things"

.

You never stop learning. I've never noticed these things before. But the initial impression is good. They are not damaged and fit well. I'll try plugging them in sometime this week and then see if the bad smell is gone. If not, I'll have to replace the trunk seal it's a disaster if you can't open the sunroof in the summer .

Hello fellow enthusiasts,

I'm one step further, but haven't had time to fix it yet. I can rule out the forced ventilation in my case. I taped it up securely -> the exhaust smell is still there. So, it's very likely the rear door seal... I'm curious to see how much it will cost at the dealership .

@haehnlein:

Quote:

I'm curious to see how much it will cost this time at the dealership

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Approximately 48 euros, plus the "absolutely necessary" special adhesive for just under 5 euros.

Roger wrote:

Around 48 euros plus the "absolutely necessary" special adhesive for just under 5 euros.

Oh dear... Well, anyway, it's winter now, so the sunroof stays closed .