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Discussion Starter · #1 ·
Is it possible to replace the media in the charcoal canister without cutting it open? Found one that is in very good condition that's complete with 0 rust. It flows air well but the filter for the media is a bit plugged up on the bottom.
 

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Stewart;

If you want to clean the screen, I expect you'll have to empty it first of the activated charcoal to get access...or maybe just try shop-vacing it and see if that cleans it...its up to you to figure out the level of insult to the canister to empty it...activated charcoal to refill is available ..aquarium supplies come immediately to mind...report back how you make out...

Cheers
 

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Is it possible to replace the media in the charcoal canister without cutting it open? Found one that is in very good condition that's complete with 0 rust. It flows air well but the filter for the media is a bit plugged up on the bottom.
Don’t think you can replace the charcoal without opening it up. I cut an approx 1” hole in the centre of the metal mesh at the bottom, emptied the charcoal and filled with charcoal pellets I purchased on Amazon . It’s a bit fiddly getting the old out and new in. Sealed the hole with a Canadian toonie and RTV. Put a piece of used charcoal fabric/mesh from my home air purifier, the W shaped retainer and reinstalled it. You can also buy open cellfoam used for window air conditioners for under the retainer. Really didn’t notice any difference, but can sleep at night knowing I’m capturing those rogue fumes 😀
 

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If you have good air flow from the bottom of the cannister up through the connection to the throttle body I would definitely hold off on eviscerating your cannister to replace the granules. Unlike the granules in aquarium filters and some other applications, the activated carbon in evap filters is generally considered to be functional forever. As long as they have been purged in operation and not been contaminated by something like oil they should be good. Don't ask me what the difference is; but, evap cannisters are definitely not on the scheduled maintenance list. When checking the purge airflow block off the evap connection to the expansion tank to make sure that you are checking air flow through the cannister.

The evap cannister(s) that were installed on the D jet are a bit of a mystery. The 140 parts manual shows a cannister that is not like the one on my 1971 142E (or as shown in the Volvo service manual). My 142 had the foam filter on the bottom, a line off the top going to the expansion tank in the trunk and a second line off the top going to a port right at the throttle body with no purge valve. The parts manual shows an evap with a vacuum operated purge valve on it being used, much like the evap on the carb equipped cars. My evap looks more like the cannister that was used on the later K jet equipped cars.

On the versions of the cannister with the purge valve the parts manual shows a separate replaceable foam filter for the purge air inlet at the bottom. The Volvo service manual (which shows my style of evap) talks about replacing the purge air foam filter at 25,000 mile intervals. However, the parts manual does not list a replaceable foam filter. MSCdirect (and probably other vendors) sells 1/4" thick foam air filter media in small quantities which might be the hot ticket for replacement of your plugged air filter.
 

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[QUOTE="142 Guy, post: 7828955, member: Unlike the granules in aquarium filters and some other applications, the activated carbon in evap filters is generally considered to be functional forever. As long as they have been purged in operation and not been contaminated by something like oil they should be good. Don't ask me what the difference is; but, evap cannisters are definitely not on the scheduled maintenance list.

The evap cannister(s) that were installed on the D jet are a bit of a mystery. [/QUOTE]

Not sure what the mystery is. I don’t think activated charcoal lasts forever , I’d like to see a reference that supports that. Activated charcoal will absorb lots of things, even when sitting on the shelf in an unsealed container. Just because they’re not on the scheduled maintenance list doesn’t mean they last forever. I suspect the layer of foam at the bottom is to limit the charcoal dust falling out. I can’t imagine a layer of foam doing anything to limit emissions. Fresh activated charcoal has to be better than 50 year old charcoal that’s been exposed to emissions all that time. Furthermore, how would one know if it’s been exposed to oil vapours, liquid gasoline or other things over the last 50 years?
 

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The mystery part was related to the fact that the parts manual for the 1971 B20E version does not show the same cannister as installed in the cars. At least for the 140, the parts manual shows a cannister for the B20E that has a purge valve on top of it. The cannister on my B20E looks more like the cannister that was installed on the later B20F Kjet equipped cars.

All of the Evap cannisters go through a purge cycle. My understanding of the purge cycle is that the hydrocarbons are drawn off the carbon surface by airflow through the cannister caused by the vacuum connection to the manifold. The released hydrocarbons are burnt in the engine. The foam filter on the bottom of the cannister may trap charcoal dust; but, its primary purpose is to filter dust out of the air that enters the evap cannister which ends up either messing up the carbon, in the intake manifold or in the gas tank as make up air as the fuel level drops in the tank.

As to the carbon in the cannister, my understanding is that it operates in an adsorptive mode rather than an absorptive mode. The fuel vapor from the fuel tank clings to the surface of the activated carbon as fuel vapors expand out of the tank and into the cannister. The vapor is not absorbed by the charcoal. When fresh air flows over the surface of the carbon during the purge the vapors are released to be burnt in the engine. The carbon does not get 'used up or wear out' if it is going through the regular purge cycle. What does kill the carbon is contamination by clogging from dust mixed with moisture (hence the foam air filter on the bottom) and other surface fouling contaminants.

Two checks for your cannister
  • is air flow through the cannister reasonable ( you are not pulling a vacuum on your gas tank)?
  • on a hot day as the vapors are expanding out of the tank into the cannister there is no refinery smell in the engine compartment?
If it passes those two tests then your old cannister is probably functioning just fine.
 

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Discussion Starter · #7 ·
Good idea Craig. So current plan of attack is to cut a hole in the center empty the contents replace with fresh charcoal place a new screen on the inside to retain the charcoal and then I assume the filter is held in by the clip on the bottom? Sadly I think the current contents of the canister have formed into one giant block as I can't hear anything moving when shaken.

130589
 

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Good idea Craig. So current plan of attack is to cut a hole in the center empty the contents replace with fresh charcoal place a new screen on the inside to retain the charcoal and then I assume the filter is held in by the clip on the bottom? Sadly I think the current contents of the canister have formed into one giant block as I can't hear anything moving when shaken.

View attachment 130589
Hi, I’ll try to attach a few pics. I used charcoal pellets from Amazon, based on the attached article.
Note the reference to evap emissions.
130605

The old charcoal poured out quite readily. Getting the new pellets in was a little more fiddly. ED06904D-AC63-4515-A66C-5CA30630FC64.jpeg
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FCBE6536-AE95-4D53-BF4F-114DD4E3B6DE.jpeg

yes, the clip holds the foam in the bottom.
good luck. I have more photos if you’re interested.


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