Hideki

So I've been trying to take care of all the maintenance issues on the 79 and I wanted to change the charcoal canister filter. Problem is, I have no idea where it is. I hope it's not on the drivers side fender area, as I see what looks like a bracket with something missing, and a plugged vacuum line... Anyone got a picture of where I can locate said filter? And if it is missing, any leads on a decent (cheap) filter and lines so I can hook the thing back up?

LudemJo

Sorry to say, that is probably what was there. On my 74, it is a small coffee can size canister with a vacuum line from the carb and vapor lines coming from the tank. Not sure where you would get one, but I would probably start with Paragon as they seem to be geared to the NCRS crowd. They do have an inventory of parted out cars too, so you may be able to score one that way that is ready to go.

John

commander_47

I believe I have the box that I took out of my car. You are welcome to it for the cost of shipping. I will look.

Remember, these boxes were filled with activated charcoal and they long ago lost any ability to filter the fumes. It's just a useless lump in the car now.

7T1vette

If the activated charcoal does not get contaminated, it will last for a LOOOONNNNGGG time. If your charcoal canister is still functional, just leave it alone. It is sealed, and you can't really get inside it without doing major surgery, anyway.

Just make sure it's hooked up correctly and that your PCV valve is in good shape. Then, if you don't get any fuel fumes in your garage after using the car, you know the canister is doing its job.

Hideki

I would definitely be interested if it's the right part.

commander_47

[QUOTE=7T1vette;1585048351]If the activated charcoal does not get contaminated, it will last for a LOOOONNNNGGG time. If your charcoal canister is still functional, just leave it alone. It is sealed, and you can't really get inside it without doing major surgery, anyway.

IF it is never used its life expetancy is forever.

This can is used to filter gas fumes from the gas tank. It is very contaminated. It's life expectancy is very short.

Can Filter 100 (840CFM) Details

The Original Carbon Air Filter.
These high quality, no maintenance, carbon air filter with a tested and true 99.5% odor removing capability and a suggested life span of 18-24 months.

Flange Size: Please Select...4" flange 6" flange 8" flange 10" flange 12" flange

Price: $359.95
349.43 USD

Unfortunately the can I have is the air reservoir for the headlights. I spoke too soon. I can't find the filter can. Probably tossed it.

7T1vette

Gas fumes go into the activated charcoal and get held there. Then, when the engine is running, those fuel fumes are sucked OUT of the activated charcoal. Fuel fumes DO NOT contaminate the charcoal. It's just doing what it is supposed to do.

Now, if the charcoal has oil/grease in it...or someone dropped their speghetti sauce in there....that's a different story.

There are MANY, MANY charcoal canisters that are still working fine after 40 years or more.

commander_47

I really hate to keep this going, but you are totally misinformed.

Activated charcoal allows molecules to stick to the charcoal. It is not limitless, nor can the molecules be easily removed.

There aren't any 40 year charcoal canisters still working that were in running cars. Fact is, most of these reached their limit after about two years.

Yes, the added capacity of the charcoal to remove odor and fumes is great due to the increased space in the charcoal, but it is not limitless.

You can check this out for yourself.
http://generalcarbon.com/activated-carbon-faq/

Here are a few quotes:

"How Long Does Activated Carbon Last?
Carbons capacity for chemicals depends on many things. The molecular weight of the chemical being removed, the concentration of the chemical in the stream being treated, other chemicals in the treated stream, operating temperature of the system and polarity of the chemicals being removed all affect the life of a carbon bed. Your General Carbon representative will be able to provide you with an expected operating life based on the amounts and chemicals in your stream."

Gasoline happens to be one of those chemicals that activated charcoal loves to stick to; along with toluene and xylene. Add to that the heat in the engine bay, and this stuff really fills up fast.

Also:

"Differently, adsorption is a process whereby molecules stick to the surface area only. As mentioned above, activated carbon has a large surface area due to being a porous material. The unwanted substance sticks to the surface area of the carbon particles."

And finally:

"How Do I Use Activated Carbon?
Carbon is typically used in a column contactor. The columns are called adsorbers and are designed specifically for air and water. The design is engineered for loading (amount of fluid per area cross section), contact time (a minimum contact time is needed to insure required removal) and pressure drop through the adsorber (needed to size container pressure rating and fan/pump design rating). The standard General Carbon adsorbers are pre-engineered to meet all of the requirements for good adsorber design."

Hideki

Okay, so I guess that bracket I saw with something missing was not for the charcoal canister in question. I was doing some more cleaning and reaching waaaay far down into the fenders and located the charcoal canister. That things going to be a pita to change the filter in that thing when I jack the car up again (I'm assuming it'll be easier to change from underneath?) I'm going to track down where that capped vacuum line goes, I'm assuming it's still for that charcoal canister.

commander_47

Sorry if your thread was sort of hijacked. Didn't mean to.

There are a ton of posts on here about the vapor canister. I don't have a diagram to post.

Maybe this will help:
http://repairguide.autozone.com/znet...52800836bc.gif

You may try starting here:

http://forums.corvetteforum.com/c3-t...gram-help.html

The vapor canister is under the left front fender. On my car it hangs under the cruise control. But I got rid of all that junk and the cruise control

The vapor canister was only meant to remove fuel fumes. It is the same stuff they put in cat litter to remove the smell. And if you have been around a cat box you know how good it works.

After the charcoal is maxxed out, it is useless. The gas fumes are all directed to the carb with no filtration at all.

You don't need it to pass emissions. It won't make any difference.

It is totally unnecessary for normal operation.

donnie1956

The can is located in the drivers fender well under the brake booster. Only way to access it is remove the rocker cover and the shield under the fenderwell behind the wheel. The can bracket is attached to the inner fender well using a couple of 10mm bolts. Look around and you will see them, may need to remove the front tire to get to them. Mine was shot in my 78 and the hoses were rotted off. I have not smelled any gas fumes before or since, I pitched it when I did my LS swap.

Vette79C3

What did you end up doing with the fuel tank line? Vent it?

donnie1956

I just ran a short vent line along the top of the tank.

Vette79C3

All connections to the canister remain in place except the one that connects to the EGR valve line which no longer exists so I plugged that port on the canister. That port would be the top left labeled Control Vac in the pic above posted by karol. I'm just hoping it does not control the removal of vapors from the canister and it's still functional. I'm guessing so since I do not smell fuel in my garage.

David Mc

79C3, the "control vac" is the purge control for the canister. The canister has a capacity to hold 24 hours of fuel vapors. After that the fuel vapors just escape through the filter on the bottom of the canister. The charcoal in the canister has extremely long life if only used to store the fuel vapors. If the charcoal absorbs liquid fuel then it will be ruined. The typical way to test a canister is to weigh it.

Vette79C3

Do I have to have the Control Vac port connected in order for the canister to function or purge the vapor?

David Mc

Yes, it would be hooked to ported vacuum.

I don't have a schematic handy but I would suspect, from the factory, GM had a temp controlled vacuum switch in the circuit also.

Vette79C3

Since that port is not connected to anything and plugged on the canister then it essentially is doing nothing. I guess my alternative would be to just vent that vapor line?

greyghost79

yes, the charcoal in that canister is toast.......... strictly ornamental now.......

David Mc

Source?

Quote from an industry white paper:

"Carbon canisters are very effective and extremely durable control technologies
with little or no deterioration of performance over the full useful life of the vehicle"