Carrera Charcoal Canister Problem and Refurb

[AHudson]

I pulled the airbox on my 3.2 Carrera recently to find a couple dozen 'droppings' from what was apparently a coal mining mouse. Solid black and crusty.

After searching and finding various threads on the mysterious 'mouse poo' in the airbox intake, it was coming from the charcoal canister stuffed well inside the passenger rear wheel arch.

As it turns out, these pellets do not 'stop' inside the airbox...

Mouse poo in my oil !!

So I decided to investigate and remedy.

If you're in the camp of "Plug the stupid thing up and store it on a shelf" you'll find little value here. But if you want to put it back as Porsche designed (similar to SCs too), here you go.

1) Why this was an issue - Please know that one of the three tubes for this canister goes into your airbox after the filter. Yes, right into the AFM/intake. After reading that this makes for spectacular fireworks if it gets superheated by exhaust, I also found some metal bits in my 'old' charcoal from the 30+ year old 'screen' supposedly holding the affair together. Not good.

2) Why this happens - There's a foam disc sandwiched between the metal screens that after huffing on gas fumes for 3 decades decides it doesn't want to be foam anymore and goes all toast on you. When it does, it collapses the tension (foam and spring thingy) causing the screens to lay down, creating a mini avalanche of charcoal mouse pellets to enter cavity where the intake pipe is happy to suck them right into your AFM/intake.

3) Other wonky issues I'm guessing at - EXHIBIT A: I'm not a mechanic, tech, nor do I play one on the forums. But my car continually smelled rich, though my AFR meter disagreed. Further, the range at idle on the meter was pretty erratic, so tuning to ideal AFR was a challenge. Though I might've tightened up some other vacuum lines/tubes in the process, this issue has abated. My theory is they're directly related.

So armed with this, I removed the canister. Pretty straightforward.

Gunky brackets, lots of wheelwell filth. Pressure wash was required for me, but I'm OCD.

I could find no reasonable way to disassemble the canister. Lubricants, prying, shock hits with rubber mallet, nothing. If you know the secret handshake, please share.

My Amateur Procedure-

1. Warmed body toward 'top' (non tube) end with heat gun. Just before it got 'shiny' I pierced with utility blade and circumcised (eww) cut the stupid top off.

2. Found massively deteriorated foam, collapsed metal discs, errant corroded metal particles inside. Poured it all in a pan to check volume for replacement.

3. Cleaned up metal. Bottom discs (tube side) way more corroded than top ones. Thus greater immediate danger for intake tube to suck them right in.

4. Cleaned living heck out of the canister, tubes, discs. Like cleaning a chimney and dampers actually. Didn't stink like fuel too bad. Tube had charcoal all in it.

NOTE: OUR HOST SELLS the canisters new. So check there if you don't want to DIY. About mid way through my obsession, I thought about this option (typical) but decided to forge ahead.

5. Purchased fuel cell foam and charcoal pellets. Cut foam in 'pac man' shape as original. I ADDED a foam sandwich in the bottom to further protect from escaped pellets. I studied the air flow and could find zero reason this would/could affect performance of the system. (see pics of entire innards, in order.)

6. Rinsed pellets in water. Let dry. Refilled pellets as original. You may not be able to see witness mark on metal tube inside, but that ended up being about the right spot, about 1 1/2" from full top.

7. Replaced upper foam/metal disc sandwich.

8. Carefully used 'black plastic epoxy' and clamped top back to body. Let it sit overnight. (pic)

9. Sanded down epoxy somewhat, sprayed with satin black plastic paint, reassembled tubes, grommets, clamps. Should be good for another 30 years or so. The foam is rated for fuel cells.

NOTE: you CAN buy 'Vapor canister filters' for many cars, but I never found one for Porsche. You could experiment and get these and fit, with far more dense mesh than my version.

> For anyone wanting to do this themselves, I bought a 5lb bag of charcoal (aquarium supply place) leaving enough for another refill plus. Also have more fuel cell foam than I will ever use.

So if you want to do this yourself, will send the 'kit' to your at no charge in USA. Just PM me with address. Consider it a gift from someone who's benefited greatly from this forum.

BEFORE and location:


Nasty, deteriorated foam which allows pellets to escape.


New foam, cleaned bits, new rinsed charcoal ready to go in


Charcoal 'fill line'


Epoxied, clamped canister


Ready to go back in:


Cleaned up, reinstalled.

[LM3929]

great write up.

Lorne M.

[Fernweh911G50]

Does this issue cause any engine damage when you see the “fireworks” from the exhaust?

[Flat Six]

Well that's just a great write-up. Thanks!

[Jonny042]

Nice job, and thanks for sharing!!!

Any idea what that canister weighs?

[88911coupe]

Wow, I may need to do this since mine has never been replaced. I assume the car should not be driven while this is out?

[AHudson]

Originally Posted by Fernweh911G50

Does this issue cause any engine damage when you see the “fireworks” from the exhaust?

Nope, it’s all in the igniting of the lightweight and super heated pellets being exhausted rearward. Probably not a good daily practice though!

Originally Posted by Flat Six

Well that's just a great write-up. Thanks!

Of course! I posted this 5 years ago, but it’s mildly timeless I presume.

Originally Posted by Jonny042

Nice job, and thanks for sharing!!!

Any idea what that canister weighs?

You’re welcome! My guess would be 3-4 pounds all in.

Originally Posted by 88911coupe

Wow, I may need to do this since mine has never been replaced. I assume the car should not be driven while this is out?

It’s mostly an antiquated pollution device, likely doing no harm if bypassed. I just figured I’d make mine work since it went goofy on me.