How to remove interior ‘crayon’ smell

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Jonoliid

New Member
Joined
Jul 9, 2022
Messages
5
Location
London
Car
C180k S204 2009
Hi all.

I posted this over on MB World. But think it’s worth sharing here too.

TDLR: The ‘crayon’-like smell in models around this age comes from the foam used underneath the floor carpets. The smell can be removed with a combination of removing the carpets to clean the foam, and airing and masking the smell. Difficulty 2-3/5 (you will need outdoor space to leave the carpets to dry & air, and between drying stages you'll need to allow the best part of a 5-7 days to finish the job).

I've had my 2009 S204 C180K for about 5 months now. Loving it so far, but the "crayon-like" old, slightly musty smell of the interior was bugging me. I don't want to drive around in what smells like an old man's car (not that a C Class estate is a young man's car either!). I had kind of got to the point of just accepting and living with it, but it was bugging me every time I got into the car, so knew I had to do something about it.

After doing lots of research to discover the source, I saw a lot of different theories and misinformation – but also no definitive solution either.

So while my wife was away for a week I decided to investigate myself and found the source.

It is not the same smell as a mouldy AC system, it's not the waxy substance around the centre console, or oil burn-off from the engine and it's not the floor mats... it is 100% the foam padding/insulation on the underside of the floor carpets. Other people have discovered this too, but it's buried within so much misinformation and incorrect theories that I thought it worth definitively answering and providing what worked for me to remove it. 2 weeks have gone since I treated and reinstalled the carpets and the smell has yet to return.

I'd identified that the smell was coming from the foam (literally by going around the interior sniffing and pulling things apart). I can understand why people think it's the wax substance or the carpets themselves as the smell obviously penetrates and rubs off onto other things nearby. Once you lift the driver and passenger floor carpets and smell the foam however, there's no mistaking that this is the source. Whether it's the glue that sticks the foam to the back of the carpet and seeps in, or just the foam deteriorating over time – it's the foam itself that holds onto the smell. I assume that this foam is used throughout the car, however (in my car at least), the smell was most prevalent in the driver and front passenger footwells, and treating these alone seems to have eradicated it. I've seen people in Thailand post about completely removing the foam and replacing with cut up yoga mats, but this seemed a bit too extreme for me. I've also seen people re-order the same pieces of carpet, only to find that the new pieces smell exactly the same.

Luckily, getting access to the foam and removing the carpet flooring is a fairly straight-forward job and largely the same process on both sides.

Things you will need:
– Flat head screwdriver
– 13mm wrench / Ratchet wrench with 13mm socket
– Dish soap/laundry detergent
– About 1 litre of white vinegar (the cleaning stuff, not the brown stuff you'd put on chips)
– A generic spray bottle and scrubbing brush.
– Around 1kg of bicarbonate of soda
– Lemon juice (optional)
– Other masking fragrances to taste (I used a combo of Chemical Guy's New Car Smell and Leather scent, plus a bit of Febreeze odor eliminator)

You can drive the car without the flooring while this cleaning process is taking place, you just need to reattach the accelerator pedal once the carpets are removed. It does feel a bit weird to drive though as you're missing padding under your foot!

Process:

1/ Crank the front seats right back as far as they will go and remove the floor mats.

2/ Next, pull up the black plastic foot guards on the bottom edge of the doorway. You should just be able to pull these up by hand as they're just clipped on. I found pulling up one side first helped release them. Once up, also pull the fabric door seals just around the base of the door opening and a little up the front side.

3/ Remove the black plastic trim on the inside wall of the footwell outer side. Removing the fabric seals should have exposed the clips for this panel. Get a small flat-head screw driver under the clips to lift them slightly to allow you to remove the panel (these clips should stay attached to the door frame, and don't need to be removed).

4/ On the driver's side, you'll need to remove the accelerator pedal (sounds scarier than it is). It's attached by 2x 13mm bolts that need removing (I kept these in my cupholder compartment for safe keeping) and a small wiring plug disconnecting. The wiring plug can be fiddly to remove. It's held on by a little clip on the top side that can be pushed down with a small flat-head screwdriver, then pulled out at the same time. Took me a few goes and some patience as it's awkward to see and position yourself to get to, but it came out easily once I'd figured it out. Be careful not to snap or force open the bit of plastic that's holding the clip in place. Once removed, the pedal will come away easily. You don't have to remove any other pedals.

5/ Remove the carpet flooring. Firstly pull the tops of the carpets free from the back of the footwells and around the sides. The carpet is literally just tucked under other bits of plastic trim, so just needs freeing. Once out on all sides, pull up the main bit of carpet itself. This is a bit fiddly as the foam is moulded in place to the metal floor, but it's not glued so just takes a little freeing and jimmying. Again, it's just kind of awkward to remove so just be patient.

6/ Once the carpets on both sides are out. Give the bare footwell a little hoover if you can, just to remove any excess musty smelling dust or bits of dirt/food that will have fallen down there, and give it a wipe down with a household spray surface cleaner.

7/ Wash the carpet flooring and floor mats. Not having a garden, I literally did this with the shower head in my bath tub. Rinsing first to get the excess dust and dirt off, then giving both sides a good shampoo and a scrub. Nothing fancy or specialised, I just used some liquid laundry detergent and a bit of dish soap. You'll see the dirt and grime come off them, even if they appear to be clean. Make sure to really push the soap into the foam on the back and scrub the surface (without destroying the foam obvs). I also had a few cracks in the foam on mine, but I was just careful not to open them up too much while washing them (they can be gaffer taped up later when dry). Once both carpets are thoroughly washed, try and push out excess water and set them aside outside with foam facing upward. I'd probably say avoid direct sunlight on them as you don't want them to bake (and for the smell to cure and get worse), but this is all based on conjecture. I don't know if that would happen or not. I luckily had a relatively shaded balcony I could lay them out on.

8/ While still damp, spray the foam and carpets front and back with the white vinegar (I added lemon juice for a little extra acidity). White vinegar is proven to neutralise bad smells and works really well. NOTE: Yes, when you first spray this, it will make the carpets smell strongly like vinegar, but this smell evaporates to nothing as it dries and thankfully takes other smells with it. It's like when you use alcohol in cooking, the alcohol burns off. Give the carpets and foam a good spray on all sides and massage/scrub in the vinegar. Leave them foam facing up again. Then sprinkle a good amount of the bicarbonate of soda all over the foam side. Don't be shy. Work it into all of the grooves and undersides with your fingers (I'll try and post an image I took of this, but the forum's not letting me right now).

9/ Sit and leave to dry. At least overnight, depending on the temperature/weather. The bicarbonate of soda absorbs the smells, and the longer you leave it, the more it absorbs.

10/ Once dry to a decent amount (doesn't have to be bone dry at this stage), hoover up the bicarbonate of soda. Once done, you can do a general smell-check to see how it's done. At this stage, mine was improved, but I could still smell it in the thicker foam areas, so elected to do the vinegar/bicarb cycle again, leaving to dry for another 24hrs.

11/ Again, once dry to a decent amount, flip them over and repeat the same process on the carpet side. You can really scrub the vinegar in on this side to get to work.

12/ Let them dry out thoroughly this time. If some areas aren't drying out, reposition so that they aren't flat on the floor. I found that that sped things up. Once dry, again hoover up the bicarbonate of soda.

13/ Do another smell check. By this point, the foam was at least 75% better and I had to really stick my nose into places to pick up the same smell.

14/ The next step is just letting Mother Nature do it's thing and letting them air out over a couple days. Really try not to skip this step as it does make a difference and it allows the carpets and foam to fully dry out. You don't want to put damp carpets back in your car and then have a different type of bad smell to deal with. I would also sporadically mist light sprays of more white vinegar over the top just for a bit of extra neutralisation. After two days of airing and further drying, I would say that the smell was 90% gone and hard to pick up even at close range.

15/ This stage is optional (I think), but I really didn't want that smell to reappear, so decided to also throw some odor masking/eliminating sprays at it for good measure. To be totally honest, I don't think any of these sprays are 100% permanent, but I figured if they help at least 5%, then it's 5% less musty smell. I mixed up a combination of Chemical Guy's New Car Smell and Leather Scent in the spray bottle (I personally don't think either is spot on: the new car smell is a bit too chemically, and the leather scent a bit too like an old arm chair than new leather, but the mix of the two seems to create a newer leather smell). I also added in a couple sprays of Febreeze odor eliminator (which claims that it does truly eliminate smells on a particle level, so I thought what the hell). The Febreeze is a bit gross/perfumy smelling though, so I only added a very small amount to the mixture so it wasn't traceable by scent. I made sure to really massage the spray smells into the foam, so that it wasn't just treating the surface.

16/ I again let this all dry out again for another 24hrs, and to let the spray smells calm down a little as they can be a bit fierce out of the bottle.

17/ While doing all of this, I was also doing the same process for the floor mats, which had obviously absorbed some of the musty smell over time.

18/ Once fully dry, I gave the carpets and foam a hoover again, just to get any residual bicarbonate of soda or dust off and reinstalled them into the car along with the floor mats.

19/ Once down and back installed in the car with the other bits of trim back in place, I gave them another light misting of the spray smell I'd mixed up, and as an optional extra set off a Meguiar's new car scent odor eliminator bomb in the car. In honesty, I kind of regret this last step, as this bomb didn't have a particularly nice scent. Too vanillary a smell compared to actual new car scent. I was able to leave the windows open a bit and wipe the seat vinyl and interior plastics down with a interior trim finisher to help calm this scent down.

Done.

As I say, the smell appears to have gone after 2 weeks since treating. My philosophy from the start though was even if I reduced it by 50%, then that would still be a big improvement and may only require very light maintenance to upkeep. However, so far I'd say the smell is eradicated 90–100%.

There is very likely other parts of the car with the untreated/cleaned foam (I'm assuming the rear passenger footwell must have some and I know directly under the front seats has, but didn't want to remove them). Obviously if you wanted to do an even more thorough job, you could look at treating these areas too.

I will keep other members posted to see if the smell returns, but so far so good.

I hope that helps anyone else looking to solve it!
 

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Stinky smell you refer to is factory stuff, you can't get rid off it.
Any car will smell from plastic-rubber components.
Have you compared a new car interior smell versus the interior smell in your car?
Does it differ?

There are no smelly free cars, everything stinks even you after a hard day of work.

If you take your car to a detailer tell them to sniff around, detailer will tell you what you should do if something is off?
Autosmart ha a fragrance machine with different scents, I love bubblegum smell but wouldn't do such thing in my car I beleive I would get constant headaches from the smell and jaw aches pretending to chew bubblegum all the time. :crazy:
 
Stinky smell you refer to is factory stuff, you can't get rid off it.
Any car will smell from plastic-rubber components.
Have you compared a new car interior smell versus the interior smell in your car?
Does it differ?

There are no smelly free cars, everything stinks even you after a hard day of work.

If you take your car to a detailer tell them to sniff around, detailer will tell you what you should do if something is off?
Autosmart ha a fragrance machine with different scents, I love bubblegum smell but wouldn't do such thing in my car I beleive I would get constant headaches from the smell and jaw aches pretending to chew bubblegum all the time. :crazy:
Thanks for your response, however I’m not sure you read any of my original post!

The smell comes from ageing foam under the footwell carpets, not the plastics or rubber. It’s not possible to compare with a new car, as the model in question is around 12-14 years old, and from what I gather the same materials are no longer used.

…And I have actually managed to get rid of the smell using the technique detailed above. I didn’t simply mask the smell as you suggest above. That’s probably why it sounds like you’ve tried and failed in the past. An odor won’t vanish if you mask it but don’t treat the source. I used a technique using household products famous for their odor neutralisation and absorption properties.

Again, this is exactly why I posted this process!

A) Because it worked for me, and B) There’s a lot of people out there posting misinformation by simply guessing the source (rather than the full scale investigation and remedy with the actual car in question).
 
I red your whole post.

My car is much older than yours and I haven't done anything to mask any smell.
Once I did try the Autosmart odor machine but used the neutral cartridge for non-smelly fragrance.

I do have some ageing must from the AC vents which I will remove with AC cleaner solvent.
This is standard for old cars and MB.

My carpets also have ageing foam, they don't smell like yours.
MB used different technology between cars.

Best thing to do is to consult an expert telling you what to do.
 
I red your whole post.

My car is much older than yours and I haven't done anything to mask any smell.
Once I did try the Autosmart odor machine but used the neutral cartridge for non-smelly fragrance.

I do have some ageing must from the AC vents which I will remove with AC cleaner solvent.
This is standard for old cars and MB.

My carpets also have ageing foam, they don't smell like yours.
MB used different technology between cars.

Best thing to do is to consult an expert telling you what to do.
In honesty, I’m not sure what to tell you or why you are choosing to argue with me on this.

You are arguing against a point on a car you admit you don’t own, about a problem you haven’t experienced and on a remedy process you haven’t tried! 🤣

As I explained in the original post, I already did the above process and it worked. The ‘problem’ crayon-like smell (which is very commonly documented on the W204) has been eradicated from my car. Therefore I don’t need to ask an expert how to do it!
I’m posting here for other’s benefit, as it’s a way to effectively solve the issue using cheap household goods and a bit of effort, as opposed to the cost of taking it to a professional detailer (which I might also point out is what a lot of other W204 owners have done in the past, spent hundreds on and not solved due to it being misdiagnosed, even by professionals).

You can believe me or not, that’s up to you.

But I’m happy to answer any questions on the process people looking to solve the same problem might have. Weeks later and the smell is still gone.

(For what it’s worth, the Autosmart odour machine will likely not work on these ‘factory’ chemical smells, as those and other ozone machines are more designed to remove bacteria-based smells such as pets smells, smoke and food smells by suffocating and killing the bacteria. And that fragrance, even if formulated to smell ‘neutral’ is still a masking agent added on top).
 
I can understand the efforts you had to go to in order to resolve this smell. I'm not familiar with the 'crayon' smell but I do know that we once bought an SLK that had been smoked in. As a hypocritical ex-smoker I hate going in any car that smells of smoke, so I was really annoyed that we'd missed it (they had the roof down of course when we viewed it). I had to take out as much of the trim and headlining as I could to wash, clean and de-odourise it.

I even used two separate treatments of an chemical 'air vidox' product that left the car smelling a bit like a swimming pool, but sadly the smoke smell still came back, even after the second treatment. I had to leave the roof down at every opportunity and just kept cleaning it over and over. We just traded it in last month after 4 years owning it and I could still get a slight whiff once in a while, so I fully understand why you'd want to remove a smell from a car. I don't understand why anyone would argue about it though; being new to this place myself I've found a couple of occasions where posters would be a bit 'blunt' on here, but generally they have been very friendly, so stick with it and I'm sure other owners will be glad of your post.
 
If this was a design flaw from MB using stinky foam or glue materials MB should have made recalls for W204 because owners would complaint.
Did they make any recalls at all?

If you have it fixed now and no stinky car no more that's all that matters!
You did a good job which MB should have taken care of in the first place.
 
Very interesting. I recently sold my 2009 CLK but I know the exact smell you are describing, the 2003 one we had wasn't as obvious from memory but that's been gone for years now.

I called my wife one day when she was in it and she'd just picked up a friend who said "I really love your car, why does it smell like crayons though?" That was exactly it! I'd never been able to put my finger on it but as soon as she said it, yeah, crayons. Ha. It wasn't bad and I was totally used to it I suspect but it's good to find out the reason. Other friends said things like "It has that Mercedes smell" as they had C&E classes of similar ages so I guess all the same materials used.
I can confirm that My S202 and our W166 don't/didn't smell like the CLKs did but again, different age and materials used.

Thanks for the info and nostalgia OP.
 
An old trick is a i/2 Spanish onion on a saucer,then placed on the floor in the rear of the car .
I prefer the smell of crayons 😆 It's interesting that something with such a strong scent can absorb other aromas though, no doubt there is a scientific explanation for it if I had the mind to investigate further.
 
If this was a design flaw from MB using stinky foam or glue materials MB should have made recalls for W204 because owners would complaint.
Did they make any recalls at all?

If you have it fixed now and no stinky car no more that's all that matters!
You did a good job which MB should have taken care of in the first place.
In China years ago apparently yes, and people complained of effects to their health. However, MB denied any health link, and it’s not something people seem to have experienced here (headaches, dizziness, lowered immune system). I certainly haven’t had any of those symptoms after owning the car for 5 months.

I don’t know if the issue in China was the same problem or even the same materials used, as the foam in European models was apparently used because of strict German manufacturing laws (apparently some VWs and BMWs of the same era have the same smell). So the China-made cars could’ve used completely different materials.
 
I am struggling with a non-smelly smell :confused:

Did you forget to blow your nose recently?
You'd be surprised how much full of cr@p nose could be stuffed with which could affect your sniffing performance. 🤣
🤣
 
As promised, I said I’d update this thread. A few months later since treating the carpets/foam and the ‘crayon-like’ smell isn’t 100% gone, but it’s significantly improved from what it was.

The big difference is that it’s gotten rid of the slightly musty older smelling scent that was part of the smell (I assume just caused by ageing foam).

So whilst a percentage of the slight crayoney smell has returned, it’s a much cleaner, newer smelling version of it. Most comments from people getting in have said that it smells like a new car.

I keep my car in a locked residential car park, so I’m able to keep the windows cracked open a touch and have kept it aired out. The crayoney smell returns a little if the windows stay closed.

But for me, this problem is solved, as it was the musty aspect of the smell that was the annoyance. Again, this seems to have been something that many other W204 owners have posted about over the years, so posting here for a definitive answer on it.

Very happy with the car otherwise. 120k on the clock and in many ways still feels like new with a few little modern upgrades (Android screen, backup camera, phone charging etc).
 
Sound like you've done some pretty extensive smell removal OP, might be worth having a look at these as a final blast to see if you can remove the last bit of your Crayola scented car! :)

UUbGl02.jpg


A previous owner of my CL had smoked in it (as was evident from a burn mark I had repaired) and although I couldn't notice a smoke smell, I wanted to be 100%. So I used one of these. You mix two pots of powder, 60ml or water and leave it to basically fill the interior of your car with Chlorine gas. It leaves a slightly swimming pool scent in the car for a few days afterwards but it's designed to remove what's causing the smell. Might be worth a shot at £15.

I just left it in my car overnight.

8cuiLFB.jpg
 
I like the clarity between 'masking' & 'eradicating' rather like dealing with the symptoms & not the source.
Yet on buying a used Mk1 MX-5 which stank of cigar smoke (the previous owner had bought it new then commuted to Greece hood up puffing all the away on a fat cigar). Thus ALL the fabric materials including the roof had absorbed the smoke. At the time not having access to professional or knowledgeable amateur advice for several days & nights I placed on a steel tray in the passenger & drivers footwell 2 incense burners !!!!!!!!!!!!!!!!!! Daft & dangerous of course yet the cigar smell disappeared never to return, nor did the car smell of residual incense. So did the burners eradicate or mask?
 

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