Vacuum Canister

[James Price]

OK...on a 78 is the Charcoal canister different from the Vacuum storage canister?

My 78 is missing a can for headlight vacuum storage..I think it's missing I can't find one?

I do have a charcoal canister down inside my fender well under the washer resovior...

My headlights wont do didley when the car is not runing...man do i feel dumb!

 

[73383]

James

The charcoal canister (vapor canister) is not the same as vacuum canister. The vapor canister is for recovery of evap. fuel vented from your fuel tank.

I don't know where the vacuum canister is on a 78 off hand. Maybe someone with a 78 will know.

Dennis

 

[yellow_2002_germany]

The vacuum canister is a longish tube in the front of the car. If you open your hood and look down the gap between the hood and front fascia you will see where the headlight vacuum tubes are hooked in, one on each side and possible one in the middle I can't recall. That is the vacuum canister. Most vacuum headlights on '68-'82 cars will not actuate without the car running since air leaks into the vacuum at varying rates on different cars. It depends on how well the headlight vacuum system has been take car of. In '78 vettes vacuum is generated off of cylinder #8, rear driver's side I believe.

The charcoal canister located behind the front wheel well on the driver's side is an emissions equipment piece. I never knew if mine worked but I always passed emissions tests in Florida (not so tough, never checked for proper equipment) and Colorado (pretty tough, proper equipment check required).

 

[78SilvAnniv]

78 Assembly Manual

I've skimmed through the Index and found the page listing Vacuum...
...but I don't see "vacuum canister".

It lists these systems under vacuum:
Power Brakes
..booster
..hose, pipes & filter
A/C
..actuator & vacuum hose routing
..control assembly & vacuum hose
..vacuum harness diagram
..vacuum water valve control switch
Headlights
..vacuum hose (engine compartment)
..vacuum hose (instrument panel)

Is the headlight actuator the canister?
Heidi

Just noticed Y2002Germany's post...I did not know that about the 'tube'...I'll look a little closer at mine.
h

 

[Stallion]

I also have a '78 and I'm not sure, but like Heidi thinks, do you mean the two headlight actuators? If you have the hood open and look down the valley of the cowl (easy to see) you'll see two large looking actuators for the headlights. Are those what you're referring to?

TR

 

[James Price]

Ok, The tube part of the frame makes sense I see the hoses running into it...what freaked me out is that I was looking through a Corvette America catalog and saw a "Headlight Vacuum Storage Canister" (looks like a coffee can) for 68 to 79 Vettes. I was thinking this was the reason my headlights were not comming up when the engine is off. (my 79's lights would come up when the engine was not running..)

I must have a leak in one of the actuators or something??


Thanks for the info everybody.

Jim

 

[Stallion]

I'm not sure that it could be the main canister logically because then the whole vaccuum system in the Vette wouldn't be working, right? So I think it would be safe to say that it might just be the headlight actuators or maybe even the relays right there. Since I just got my Vette last weekend, I haven't gotten the chance to get the experience of figuring out where a leak in the vaccuum might come from. So I guess I'm not too much help.

TR

 

[wicky88s1975]

To address the original question, The canister in the fender under the washer fluid reservior is the characol canister for the emmission system ( fuel vapor recovery).


The vaccumn reservior for the headlights is located in the front bumper. it holds a reserve while the car is running to work the headlight accuators. These do not work when the engine is off at least they don't on my 75.

There is another vaccumn reservior on early c-3's that worked the windshield wiper door. Your 78 won't have that. May be there was a typo in the description of the part, or the part does double duty as a headlight assembly part.

 

[yellow_2002_germany]

As far as I know the vacuum reservoir does not do double duty. It sole job is to stay empty! LOL

On a '78 each headlight has 1 actuator relay valve and 1 control actuator. It is quite possible some of the rubber seals on the control actuator have dried out. Also, the relay valves don't have any user serviceable parts and have to be bought as a unit.

From the looks of the drawings in my Eckler's catalog, the Vacuum reservoir tank that you might be talking about is for 80-82 vettes.

My guess is that the longer tank on the '78s and other years is not serviced as a separate part.

 

[Stallion]

Okay, I was just in my Vette and I took a picture of the front with the hood open so you can see the two headlight actuators. From what I know, I don't think you can see that vaccuum relay from this view. Hope this picture helps any...

TR

 

[JohnZ]

All C3's have vacuum "actuators", the big cans with diaphragms in them and rods that operate the headlights (and wiper doors on earlier cars), and they also have vacuum "reservoirs", which store a constant supply of vacuum so the function of vacuum-operated devices doesn't change due to changes in engine load, which changes the level of vacuum available. The "reservoir" was usually essentially a big black-painted coffee can, and they tended to rust out fairly quickly; some people spent the money to replace them when they rusted out, and some people just disconnected them and ran the vacuum supply direct from the intake manifold, bypassing the rusted-out reservoir.

 

[L82Dan]

The way I understand the headlight vacuum system is that the engine must be running to actuate pop-up function. Manifold vacuum is used to acutate those round gold devices under the hood at the front of the car. They will work immediately after the car is shut off, but the system will have just enough vacuum for one function, either to open or close them. My system usually bleeds off quickly, so I get one shot at closing them. There is no storage canister for them that I know of. If you have problems with getting them to function properly, look at the hose for kinks in them. It doesn't take much to cause them to not work correctly. Just my input for what it's worth.

 

[Stallion]

All C3's have vacuum "actuators", the big cans with diaphragms in them and rods that operate the headlights (and wiper doors on earlier cars), and they also have vacuum "reservoirs", which store a constant supply of vacuum so the function of vacuum-operated devices doesn't change due to changes in engine load, which changes the level of vacuum available. The "reservoir" was usually essentially a big black-painted coffee can, and they tended to rust out fairly quickly; some people spent the money to replace them when they rusted out, and some people just disconnected them and ran the vacuum supply direct from the intake manifold, bypassing the rusted-out reservoir.

John, where exactly is this reservoir, anyways? I was looking under the hood and is it on the passenger's side pretty close to the windshield? Not sure, but that part was un-identifiable to me so I'm just wondering. Thanks!

TR

 

[wichitacorvette]

Dan is right. the engine has to be runnign to have a vacuum to set the actuators and lift the lights....... as far as the "coffee can" youre talkign about, ya, it doesnt do anythign, its a glorified coffee can w/some innards that i think gm made out of old pop cans..... anyway, i replaced the coffee can with a crane cams vac reservior and my lights worked alot better....... but they wont work w/o the motor runnign, kinda sucks if you turn your car off without shutting off the lights....... nothign more embareassing than having to turn your car back on in public to drop those pop-ups..... if your lights work well and come up easily with the car on, be thankful. from what i hear that doesn thappen often.. as mine didnt till i replaced the reservior...... if you have a stock motor you wont have to do what i did, but if you have a vacuum draining cam, you prob will..... ... hope this helps......
Tony

 

[JohnZ]

John, where exactly is this reservoir, anyways? I was looking under the hood and is it on the passenger's side pretty close to the windshield? Not sure, but that part was un-identifiable to me so I'm just wondering. Thanks!

TR

It's mounted on the back side of the driver's side front wheel well; earlier cars have a squarish metal tank, later ones have a cylindrical metal tank. Just follow the vacuum hose from the fitting on the intake manifold behind the carburetor; it goes through a plastic filter, then a metal check valve where it splits into two hoses - one hose heads for the firewall and goes inside the car, and the other one goes to the vacuum reservoir.

 

[wichitacorvette]

thats really jus the fuel vapor tank..... it doesnt really hold any vac..... i looked in my shop manual and theres a valve that doesnt let the vac out of the can, the other hose that connects to the pcv and fuel vapor prevents it.....

 

[Dave L.]

The 80-82 models used the "coffee can" resevoir(as John Z stated), mounted under the front bumper cover (see attached photo). They don't show one used on any other years but the 80-82 models.

Dave

 

[78SilvAnniv]

OMG!

Is that REALLY a Folgers can painted black!!!??? :eek
Heidi

(it sure looks like it)

 

[wichitacorvette]

ya i think it is....... lol if you ever replace that thing be sure to pull apart the old one, its such a "engineering accomplishment" inside lmao :L :L :L

 

[vigman]

Ok in review ( vacuume tanks)

the EARLY C-3's had a canister located behind the front fenderwell ( drivers side I believe)
you can see it through the air vents behind the front wheels.(68-72?)

later C-3's had it built into the foward frame..just a big long round tube going from left to right on the ladder..just before the bumper brackets.(73-79?)

Even later C-3's had the HI-PO Hills bros coffee cans ( to compete with Ford's Folgers cans)( 80-82?)

Did I get that right?

Vig!