Hello all. I'm new here (used to hang out on the
VetteNet list years ago). Still have both of my
sharks ('68 roadster and an '81) but other "hobbies"
have kept me pretty busy.

Anyway, this will be the 3rd vacuum reservoir in about 10
years that has started leaking again on my '81, and it's the
2nd reservoir I've purchased new from a Corvette parts place.
I've since read elsewhere on the net that the 80-82 "coffee can"
vacuum reservoirs are notorious for leaking (poor design).

There's no room underneath the LH front fender to retrofit with a
68-72 reservoir, but I was wondering what the configuration was
for the '73 - '79 Vette, and if I could somehow use a vacuum reservoir
off of one of those? (the same net source that said the 80-82
reservoirs leaked didn't have anything bad to say about the earlier
examples).

I'm also wondering what the original intent of the reservoir
was in the 1st place? I'm guessing it's purpose was so you
could operating the headlight doors and/or windshield wiper
door (on early sharks) once or twice without the engine running.

Is there any reason I can't connect the vacuum lines directly
to the headlight door relay/regulator and sh_tcan the problematic /
leaky reservoir?

TIA for any advice,

Bela P. Havasreti

 

How can you tell that it is leaking? I think mine might be leaking too. Car runs choppy when I start it until I rev it up. Am I starting with an empty reservoir? Also when I put the headlights up or down especially after starting it runs choppy for a few seconds. Car has 196k and it might be leaking. Are these expensive? I don't think the car acted this way from the factory.

 

79 vac reservoir is in the front frame section, underneath the headlights / in front of the rad support. I doubt it could be attached to an earlier or later shark, it's part of the frame.

yup that's right

so long as you have no reason open/close the lights w/o engine running you can sh_tcan the reservoir if you want.

 

I use the extremely scientific "pinch the hose" method.

You take some needle nose pliers, start at the source
of vacuum (in this case, the intake manifold just aft
of the carb base) and pinch off each section of hose
until the car idles better.

If I pinch off the hose going to the reservoir, the
idle gets better very quickly. Let it go, I'm back to
a choppy idle (vacuum leak). I've tested the headlight
door relay + actuators with a hand-held vacuum pump
and they're fine (they hold vacuum).

I also have a vacuum gage + venturi-based vacuum source,
and I tested the previous reservoirs after I pulled them (they
wouldn't hold vacuum), but I haven't pulled or tested this
reservoir yet.

New reservoirs are about $85 (mind you, this is for a bloody
coffee can rattle-can painted flat-black!). With a new
one (or one that seals well), you won't get any of that
choppy idle while operating the head-lights. I'm just getting
tired of spending $85 each for a new reservoir every 2-3 years....

Another tell-tale sign that something is leaking in the headlight
vacuum circuit is if the headlight door(s) pop up on their own
during extended periods of WOT (like when passing or "having
fun" during a long upgrade / hill). The way the system is designed,
the vacuum source keeps the doors closed (they're spring-loaded
to open if the source of vacuum fails). Here's a web page that
has some good stuff on the system:

http://www.jamisoncustomcorvette.com/head.htm

Bela P. Havasreti

 

Thanks Star79. I'm normally not one to "butcher up"
a Corvette, but I think I will by-pass the reservoir
for now (I'll leave it in there for the next victim!)

Bela P. Havasreti

 

Can you bypass the reservior on the 77-79 models as well if you don't want to open or close them without having the car running?

 

The reservoir on my '81 was also leaking. Do you know where it's leaking from? Mine was under the vac pipe fitting so I, er, (I hate to say this, Bubba & all that), covered it in a thin layer of epoxy & then painted it black (I refuse to pay so much money for a catering size baked bean tin!). It fixed the leak, the bodge can't be seen, the idle is great but the headlights don't open/close without the engine running.

 

Both of the previously failed reservoirs failed at the bottom
forward edge of the "coffee can" (the roller seam-weld, or
whatever manufacturing method they used split / failed).
I haven't pulled this one out yet to see where it failed.
I'm happy to report that per user Star79, the headlight
doors are perfectly happy with getting their vacuum source
straight from the intake manifold. I put a T fitting on the
hose that used to go to the reservoir and hooked the outlet
hoses (which feed the dual headlight vacuum relays) that used
to go from the reservoir to said T fitting . Works like a charm,
no vacuum leaks.

The 1st time the reservoir leaked, I attempted a fix similar
to what you did, but it ended up leaking again in short order
(I used 5-minute epoxy). Shoulda used the butcher's shmooey
of choice I guess.... (JB Weld!).

Bela P. Havasreti

 

There are 2 canisters on the vette, the one for the headlights under the nose and the one for everything else in the fender. I had to replace my headlight one and I pretty much made my own with a coffee can of similar size. Too bad I had to ditch the coffee since I cut through the top with a hole saw.

 

what was inside ?baffles ,anything or was it just a open can ?they cost alot i would like to find a plastic replacement.

 

It's just a coffee can, nothing inside... I cut the origional fitting with the lid off with a can opener, cut a 2" hole in the new coffee can (dumped out the coffee) and JB welded the old top to the new then painted it with rustolem paint...

 

3quarters,
What year vette are you talking about? I thought the can in the fenderwell of my 79 was just for emissions? I currently have it disconnected and am also having vacuum issues. I do have the large reservoir up front and thought that was all I had.
Thx , ESU

3 quarters?? NY location, disability pension??

 

The one in the front of the car is strictly for the headlights, I too was having vacuum issues and it came down to my can in front being riddles with holes. Someone tried sealing them up before I got the car....

I need to get the one in my fenderwell out also, I'm still having a bit of vacuum issues and I think that canister may be the culprit...

I'm in Nassau and Yup....

 

thanks with as much coffee as i drink i should have enough coffee cans to supply the forum for years.

 

The canister under the driver's side fender is for emissions. The one under the nose is for headlight vacuum. Many have scrapped the vacuum canister and directly connected the headlights to a vacuum source. Nothing wrong with that except the headlight will only work when the engine is running.

The emissions canister is used basically to capture gasoline vapors out the carb and I believe the gas tank. It is open to the atmosphere. There is granulated charcoal in this canister with a filter on the bottom. To get the emission canister out, I found that going through the side fender vent to be the easiest method of extraction.

Good Luck!



Jay

 

Thats what thought about the fenderwell can. Just as an aside to this thread, I purchased off ebay a used vacuum pump from a volvo. Made by Hella and cost me 40 bux. Then I found a used Volvo parts site where I could have paid $15.00, Oh well They use them on diesel cars to supplement the vacuum for cruise control and other options. I'm going to mount it on the drivers side fenderwell and tie it into the vacuum line to supplement my low vacuum. I'll see if this helps with keeping my a/c flowing thru the dash instead of the floor when I turn the headlights on. Should also help with the cruise when I get that running. Has an auto shutoff when it gets to 20 inches. I'll get it in in about a week and see what happens,
ESU

 

the cannister in the fender is for emissions but, i did find the vac lines leaking ,changed all of them and it did help the cruise control be more steady.

 

Yup, the fender cannister is for gas fumes. Mine was leaking slightly from the underside seals on the two vac valves/switches on the top, so it's worth checking for leaks there. It didn't really affect the idle that you'd notice, but after fixing the leaks there was a definite improvement in idle quality.

 

Hi everyone so Im finally starting to buy the parts to work on the vacuum system, I have a 1981 I found the headlight reservoir tank that goes between the headlights on ecklers but I also see another tank or reservoir in the drivers side fender area does anyone know what this one is called?

 

Hi everyone I finally started buying the parts for the vacuum system on my 1981, I found the vacuum reservoir tank that goes between the headlights on ecklers but I also see another tank/reservoir in the drivers side fender area with a whole in it but I don't know what this tank is called, if anyone can help please let me know?