where is the vaccuum resevoir located?

[goertz]

the headlights on my 73 come up very slowly about 1/2 way, and you have to help them up the rest of the way. once up, they stay up. i think there is a vaccuum leak at the resevoir, as when i shut the car off, i hear a hiss come from the drivers side of the car for a few seconds. i was just wondering where to look for the vaccuum tank. maybe it leaks, or has a bad hose.

 

[Bill75]

I believe it's right in back of the front bumper. One of the bumper supports is welded to it, look up thru the large openings in the valence.

Inspect the vacuum actuator on the headlight mechanism, the diaphram may be bad also, this part:

http://www.ecklers.com/product.asp?pf%5Fid=A8257R&dept%5Fid=1477&mscssid=CD9VHT336QSR2L8F00N0SM2EP30T4RB8

 

[srs244]

it is mounted right in front of the radiator and looks like a metal log that runs from side to side mounted on the frame cross member. you should be able to see it with the hood in the open position by looking down past the headlight door actuators . it can not be seen by looking for it forward through the open hood via the engine compartment as the radiator is in the way. i would doubt that the tank is bad, however, since it was strengthened and enlarged from the "tin can" type that was up under the driver's side fender on the late 60's c-3's. i would suggest you look closely at the hoses running from the manifold vacuum source through the line filter and to the check valve and beyond. more likely than not, you have a bad hose or "t" connector. a new set of headlight vacuum hoses can be purchased in a kit that includes all the hoses and connectors to replace everything and is available from a lot of supply companies for around $45-50. personally i suggest you consider the set from dr rebuild. i have found it the most correct (hose size wise) kit but that is just my opinion.

i also agree that the actuator seal could possibly be at fault if the hissing seems to be coming from the front area. the best way to inspect them would be by removing the grills and having someone turn on the lights (since there is not a lot of vacuum reserve chances are that the over ride switch is probably useless in this case), while watching the movement and listening on each side from the front through the grill openings. you should also be able to make a physical inspection of the boots and seals at the same time. figure on approx $12.00 each for a boot and seal. they both can be changed throught the grill without removing the actuator. be careful when you slide the seal onto the actuator shaft as you do not want the threaded end of the actuator rod to "rough up" the seal end and cause it to not seal correctly. 2 tricks to use: heavily coat the threaded portion of the rod with liquid hand soap to lub the seal on the way on or place the seal over a plastic drinking straw then slide it all over the rod. once seated, pull the straw out over the rod saving the seal end.

hope that helps you out some.

 

[goertz]

hmmm, maybe it's not the vaccuum tank then. perhaps the hissing is coming from the light switch itself. i definately think it's just not enough vaccuum getting to it. you can turn on the headlights, they'll pop up about 1/2 way evenly, but not enough vaccuum to get it up all the way (i thought when you drive a corvette you should always be able to get it up). then, if you are driving, and bury your foot in the gas pedal, as soon as you let off, and you get that rush of vaccuum when you let off, they pop right up. regardless, the dealer i bought it from has agreed to fix it, but if it's something simple, i'll just fix it myself, and save driving to Denver to drop it off, then pick it up. the dealer is a Corvette only dealer, so they know all about these things, so i'm sure the repair would be done right.

 

[jdp6000]

Its potentially an easy fix. The hoses go to two places in the cockpit. One spot is directly under your steering column...it has a up/down rod type shaft...this is the headlight switch bypass (try pulling the switch/rode up and down and see if anything changes). The other connection point for the hoses is the headlight switch...I believe two hoses go to it...sometimes the come off partially and cause a leak.

so...listen carfully for the hissing...is it coming frome under the steering column or up higher near the switch? Once you have figured it out. drop the access cover directly under the steering wheel...repair...reattach etc what ever is causing the leak.

Jim

 

[goertz]

Its potentially an easy fix. The hoses go to two places in the cockpit. One spot is directly under your steering column...it has a up/down rod type shaft...this is the headlight switch bypass (try pulling the switch/rode up and down and see if anything changes). The other connection point for the hoses is the headlight switch...I believe two hoses go to it...sometimes the come off partially and cause a leak.

so...listen carfully for the hissing...is it coming frome under the steering column or up higher near the switch? Once you have figured it out. drop the access cover directly under the steering wheel...repair...reattach etc what ever is causing the leak.

Jim

we were hoping pulling the bypass would get it going, but it didn't. i'm thinking leak at switch hoses, or perhaps the hissing was from the brake booster. the car kinda runs like it has a vaccuum leak, and the hissing might have been coming from there. i would think a sizeable leak anywhere in the vaccuum system would cause the lights not to open. the brakes feel about normal, but maybe a little on the hard side. each car varies, so it's hard to tell for sure. tonight i'll plug the hose to the booster and see if it runs smoother.

 

[jdp6000]

Where is the hissing coming from?

Jim

 

[goertz]

it almost sounds like it's coming from outside the car, drivers side. definately not at the front, more like around the cowl area. when driving or idling, you can't hear it, but when the engine is shut off, you hear it leak out the remaining vaccuum from the system.

 

[srs244]

the various vacuum driven parts almost all have their own manifold vacuum connection. if too many are open at the manifold, the engine would run pretty rough. as far as a vacuum problem somewhere else effecting the vacuum system and reserve tank of the headlight system, i doubt it. it would have to be part of the system specifically connected to the headlight vacuum system. that leaves the headlight switch (as previously mentioned it has 2 connections to it. one from the engine compartment, one from the bypass switch), the bypass switch (one hose from the engine compartment, one to the headlight switch), all the hoses and "t" type connectors, the check valve and filter, or something associated with the actuators (the seals or the cases themselves). if you think you hear the hissing from inside the cockpit, it would have to be either of the switches (bypass and headlight) or one of the hoses associated with either of them. if you hear it outside the car, if you hear it back towrd the firewall, it's probably a hose or connector. if you hear it toward the front, it could be a seal, or vacumm hose. you might also have a leak at the vacuum relay, but that also would be up front. as previously stated it is usually a hose or an actuator seal that causes the problem.

 

[goertz]

the only reason i thought maybe brake booster, was because that's the only vaccuum operated gizmo that takes enough of the engine vaccuum that rough idle would be caused if it leaked. a leaking booster would for sure cause rough idle, and might be leak enough of the vaccuum that other systems would be effected. if you pull your booster hose off the engine, your car will barely idle. i'll have a good look over it tonight to see what's going on. worse case, i'll just take it back to the dealer and have them fix it. i made them put it in writing that they would fix the headlights, regardless of cause. actually they offered, as it's a safety item.

 

[jdp6000]

Thats easy to diagnose. The hose that feeds the headlights is to the rear driverside of the motor, one hose comes out of the intake and goes into a saucer shaped thing, I believe two hoses come out of the saucer shaped thing.

The brake booster hose connects to a fitting on the brake booster. That fitting is only a oneway valve (in only). Take it off. if you can blow both ways thats your problem.

Other possiblity is a leak in the line where it goes into the firewall.

Try spaying a bit of water on the hoses (look for bubbles) or use a lighter and see if it blows out.

 

[Lucky 3]

on my 72 the vacuum res is located under the left fender, behind the front wheel well. looks liks a 3 pound coffee can painted black. very had to get at if you have power brakes. Start checking all of your vacuum lines. Bill

 

[goertz]

and that is exactly where i hear the hissing when i shut the car off. i'll have to get a flashlight, and have a better look in there.

 

[red70vette]

You need to get an AIM or some type of manual for your car. The vaccuum res. on my 70 is also located under the fender behind the front wheel well. That doesn't mean it is there for a 73 as evidenced by srs244's whose is in front of the radiator. Check the hoses to and from the Vaccuum res. A good investment for a Corvette owner is a vacunm pump like a mighty vac for testing for those leaks.

 

[wishuwerehere82]

You can try to isolate the sound by running your hand back and forth around the area the hissing sound is coming from. When the sound quiets, your hand is between the leak and your ears. Once you find the can, run your hand around it and it will stop hissing when your hand is over the leak. A glob of JB weld will plug it until you can a replacement.

 

[lucky76]

Charcoal canister

on my 72 the vacuum res is located under the left fender, behind the front wheel well. looks liks a 3 pound coffee can painted black. very had to get at if you have power brakes. Start checking all of your vacuum lines. Bill

That coffee can is your charcoal canister for fuel vapors from the gas tank. It is on mine, and I just replaced the vacuum hose from the carb to it and the other hose to a metal line down the frame to the gas tank. Your probably loosing so much vacuum that the lights won't pop up. Mine wasn't even connected to the carb and I could smell gas all the time.

 

[srs244]

on my 72 the vacuum res is located under the left fender, behind the front wheel well. looks liks a 3 pound coffee can painted black. very had to get at if you have power brakes. Start checking all of your vacuum lines. Bill

the vacuum reserve tank on your 73 is definitely as i described. a log looking metal tube mounted in front of the radiator down under the headlight actuators. i believe (but am not certain) that the late 60's style reserve tank located within the drivers side fender was replaced in either 71 or 72 with the tank i have described. i know for certain that a 73 has the tank located in front of the radiator and looks like a metal tube or log. the "saucer thinggie" described by someone is one of two items. they were describing either the filter or check valve. the filter is a simple plastic piece with a screen in it to filter the vacuum on the way to the exhaust manifold. the check valve (metal with one feed into it from the line coming from the filter and 2 lines out from the other side) is what maintains vacuum in the reserve tank by restricting "back flow" of the vacuum created. both of these parts are located in the main vacuum line from the manifold to the first "t" type connection right in front of the brake booster. those "t'ed" lines go into the passenger compartment to feed the over ride switch (and the headlight switch) and forward along the driver's side fender toward the actuators and reserve tank. it could explain why you think you have a brake booser "leak" as the headlight vacuum system is routed right there also. (please appreciated i am not discounting the fact that you may actually have a brake booster leak, but you would certainly be aware of it if you did in the form of a very hard to stop vehicle and a very poorly running (and idleing) vehicle).

 

[goertz]

That coffee can is your charcoal canister for fuel vapors from the gas tank. It is on mine, and I just replaced the vacuum hose from the carb to it and the other hose to a metal line down the frame to the gas tank. Your probably loosing so much vacuum that the lights won't pop up. Mine wasn't even connected to the carb and I could smell gas all the time.

do 73's have that? I can smell gas too.