Vacuum Hoses Or Not?
Thread Starter
Burning Brakes
Joined: Nov 2005
Posts: 832
Likes: 1
From: Breckenridge Colorado
Vacuum Hoses Or Not?
Last night I found a hose that was not plugged and not attached to anything. I attached a pic to describe where the hose was located but I can take a real pic when I get home tonight if you can't tell what I am talking about. I thought it looked like a vacuum line which is why I was looking at the vacuum troubeshooting at http://www.corvette-101.com/ and used the pic there to show where it was. Underneath the brake master cylinder at the bottom of the engine bay there is a metal cylinder with three hoses comming off of it. One of the hoses travels the drivers side fender up towards the headlight and then just stops about 2 feet short and is not plugged or capped or anything. Should this hose be connected to something or is it possibly a vent hose?
Last edited by MartyW; Jul 17, 2006 at 11:30 AM.
Instructor
Joined: May 2006
Posts: 168
Likes: 0
From: Florence NJ
Sounds to me like the charcol canister. It is used for emissions. This is not needed but at the same time you will not gain or lose HP by connecting it or scrapping it, so you should probally hook it back up. Not to mention it will help prevent vapor lock too.
One hose goes back to the gas tank and one up to the carb. The third I believe just sits open but I don't remember 100%.
If you are going to leave it disconnected, make sure your carb port is capped off.
Jim
One hose goes back to the gas tank and one up to the carb. The third I believe just sits open but I don't remember 100%.
If you are going to leave it disconnected, make sure your carb port is capped off.
Jim
Thread Starter
Burning Brakes
Joined: Nov 2005
Posts: 832
Likes: 1
From: Breckenridge Colorado
ALOT of the emmission stuff on this car has been disconnected so that would make sense. I am pretty sure it is plugged at the carb. Should I plug the hose or remove it?
Instructor
Joined: May 2006
Posts: 168
Likes: 0
From: Florence NJ
I would just hook it back up because it really dose not effect horse power at all. But if you do not want to hook it up, you could just leave it as is. See it works like this, at the tank there is a part that has, for simplicity we'll call it a check ball. A line goes from this part up to the canister. It allows vapors to flow out of the tank to the canister but will not allow any thing to go back into the tank. So if you cap this line off that goes to the carb you could get vapor lock and the car will stall out ant not start back up.
So in my opinion, just leave it open. I'm sure others may have oppinions on this too, but that is just how I feel about it.
Jim
So in my opinion, just leave it open. I'm sure others may have oppinions on this too, but that is just how I feel about it.
Jim
Thread Starter
Burning Brakes
Joined: Nov 2005
Posts: 832
Likes: 1
From: Breckenridge Colorado
Two of the three hoses are still connected up, but the third one is just hanging loose and that was the one I was worried about. If I should hook it back up....where does it go? Or should I just pull off the plug at the canister that way it does not look wierd that it is going nowhere.
Thanks for the help.
Thanks for the help.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
There should have been a sticker under the hood that gives you all the vac line connections, I think my 81 has like 6 hoses on the canister. Smart money says hook it up correctly, it does some good and doesn't do you any harm. There is also a detailed diagram in the shop manual for your specific year.
Thread Starter
Burning Brakes
Joined: Nov 2005
Posts: 832
Likes: 1
From: Breckenridge Colorado
Originally Posted by jeckel
if you pull it off I suggest not capping the can, just leave it open. If you want to hook it back up, it should connect to a port on the carb.
Thanks Again, My Chiltons did not help me too much in even finding what that part was.
As for the diagram under the hood....no luck there. Not original hood either and no stickers on it. I can look at it when I get home, but pretty sure there were only 3 hoses comming from it.
Last edited by MartyW; Jul 17, 2006 at 01:24 PM.
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Instructor
Joined: May 2006
Posts: 168
Likes: 0
From: Florence NJ
What year is your vette? and did it have an air pump on it? I'm not 100% sure but I am thinking the 3rd line may have something to do with the air pump.
Someone with air pump knowlege please chime in on this.
Both my 74's only have 2 lines on the can to the best of my recolection and neither had air pumps but i'll double check for you tonight. just a thought, hope it helps
Someone with air pump knowlege please chime in on this.
Both my 74's only have 2 lines on the can to the best of my recolection and neither had air pumps but i'll double check for you tonight. just a thought, hope it helps
Last edited by jeckel; Jul 17, 2006 at 04:33 PM.
Melting Slicks
Joined: Dec 2000
Posts: 3,407
Likes: 2
From: Carmichael CA
It sounds like someone has replaced that canister with a different one. Your evaporated fuel reservoir should only have two hoses...one goes to the top of the fuel tank and the other to a vacuum port on the carb. The 3 port canisters were OEM in 72 which had a third hose which I believe was a vent. But, look at that cannister real close because in 78 the canister appears to have gone to 4 or 5 hoses. Consult Chilton's Repair Manual on pages 4-36 through 4-45.
Thread Starter
Burning Brakes
Joined: Nov 2005
Posts: 832
Likes: 1
From: Breckenridge Colorado
Ok I just got home and was able to check the hose again. It is definately the evap canister and there are only two hoses comming from it and one definately goes back to the gas tank. The other hose is the one that is not going anywhere. This is the one that should be going to the carb (from what everyone else is saying). Where on an Edelbrock Performer series carb would the correct port be for it to connect to? I am gonna assume that it has never been hooked up since the engine was rebuilt, but I could be wrong. From what you guys are saying I should definately hook it up as I would lose NO power and could benefit from other problems that can arise without using it.
Thanks Again - Hope to see as many of you as possible for 'Vettes On The Rockies' up here in Breckenridge Colorado in about two weeks.
Thanks Again - Hope to see as many of you as possible for 'Vettes On The Rockies' up here in Breckenridge Colorado in about two weeks.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Originally Posted by MartyW
Is this where the hose from the evap canister connects to the carb?
Last edited by ...Roger...; Jul 17, 2006 at 09:17 PM.
Thread Starter
Burning Brakes
Joined: Nov 2005
Posts: 832
Likes: 1
From: Breckenridge Colorado
Originally Posted by dwncchs
Wait -whats the diameter of the hose?
Thread Starter
Burning Brakes
Joined: Nov 2005
Posts: 832
Likes: 1
From: Breckenridge Colorado
Originally Posted by dwncchs
I was thinking it was a vent hose 3/8 diameter.Forget what I said before I was on the wrong track.Sounds like you need a vacumn source.
Melting Slicks
Joined: Dec 2000
Posts: 3,407
Likes: 2
From: Carmichael CA
Originally Posted by MartyW
If that port on the carb is 3/16 what do you think it is for? There is definately no other place I can find to plug any hose into on the carb.
It really doesn't matter what the vacuum signal is...the weaker the better in my opinion. So, if you have a vacuum gauge then look for a weak signal. But, don't connect anything else up with that vacuum line and don't use a rubber hose...it must be fuel line since it will be carrying fuel vapors and will eat up any rubber on contact. I'm not familiar with Edelbrock carbs, but I suspect that if you do have one port which is plugged then that will be the port for the evaporation canister. You can also use manifold vacuum as long as no other vacuum lines are connected to it.
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
Sorry if I confused
Marty-sorry if I gave bad info.I had in my brain your canister "did not" have a purge valve on top of it.Sounds like it does.(maybe we could have used a pic of canister)My main concern was focused on keeping the vent to your tank open-(if your tank is not vented you can starve your engine of fuel and sometimes even crush the tank.)I cant find (in all my info) anything on 1976
I'm still a little confused about your canister.I thought if there was a purge valve there would be a hose to the carb by which it would be purged- in other words a min. of 3 hoses(inc.top and bottom)-1 hose to tank as a vent(5/16 or 3/8)-1 hose to carb or a T with PVC to serve as a purge source(5/16 or 3/8) 1 smaller hose say 3/16 that signals purge valve to open and purge or clean charcoal canister.Bottom line (like RocknRoll and Jeckle said)make sure you have a vent for the tank and its open.Again sorry if I made this more complicated than it has to be-but GM seemed to change this every year and lots of people just took them off because they were misunderstood.They dont hurt performance if hooked up right.
Roger
I'm still a little confused about your canister.I thought if there was a purge valve there would be a hose to the carb by which it would be purged- in other words a min. of 3 hoses(inc.top and bottom)-1 hose to tank as a vent(5/16 or 3/8)-1 hose to carb or a T with PVC to serve as a purge source(5/16 or 3/8) 1 smaller hose say 3/16 that signals purge valve to open and purge or clean charcoal canister.Bottom line (like RocknRoll and Jeckle said)make sure you have a vent for the tank and its open.Again sorry if I made this more complicated than it has to be-but GM seemed to change this every year and lots of people just took them off because they were misunderstood.They dont hurt performance if hooked up right.Roger
Last edited by ...Roger...; Jul 18, 2006 at 08:36 AM.