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Headlight vacuum hose check

T

t78

Guest
Which headlight vacuum lines should I close off/disconnect to determine if my rough idle has anything to do with headlight vacuum leaks. I searched the subject, and have the diagram shown on the L81 Registry site.

It takes a long time for them to pop up, and go down (especially if the engine has been running for awhile) - and someone told me that if there is a leak, my engine will not idle well. -Which it isn't, and I haven't figured out why yet. (Still have to hold the brake with left and give it a little gas with the right while I'm at a stop light...)

Thank you, :)

t78

-78 Pace Car
 
C

CSCARLSON

Guest
have you checked you vaccum canister for leaks? mine was bad and it did the same thing
 
Joined
Jun 5, 2001
Messages
2,231
Location
Northern Virginia
Corvette
71 Conv. (Sold) / 98 Pewter Coupe (Sold)
Another cheap trick to try is checking the ends of each line at all of the connections to see if they feel dry. If they do, they aren't going to seal good. I trimmed about a 1/4 inch off of each of my lines cause the very ends were brittle but the rest was fine. I then sprayed silicone on the ends and now my lights (and wiper door) pop up a lot better. I still have some more work to get them perfect, but that was a cheap stop-gap measure that made a great improvement.

Good luck!:s
 

1979toy

Well-known member
Joined
Mar 20, 2001
Messages
263
Location
Wichita, KS
Corvette
Red on Red 1979 L-48
Do you have a vacuum gage? A vacuum pump? Both tools will be helpful in finding your problem, or problems.
On the intake manifold between the carb. and dist. you will find a 3 way vacuum port. One of those hoses goes to the one way check valve for the lights (round part 1 hose in 2 out). Pull the hose where it goes into the check valve from the manifold and plug the hose. Start the engine, if your idle improves you've found your leak. It is somewhere past the check valve. Now you have to work your way down the hoses until it is narrowed down to 1 part. This is where a vacuum gage will help and pump will help. Warning! The check valve it's self can be bad. Guess how long it took me to find that problem on my car.:confused
Good luck with it.
 
T

t78

Guest
Well, so far I have found one line that was broken, but it wasn't on the headlight system. As far as I know, it is the hose on the fuel vapor canister going to the gas tank (No wonder my garage stinks like gas all the time...) I pulled the cansiter out, and I am going to try and clean the little filter on the bottom - it was full of bugs and stuff. Hopefully this line is one of my major causes of problems.

1979 toy, thanks for the info on the vacuum system. I couldn't find that anywhere. Once I hook the canister back up, I will try to start it again with that line plugged off - and put it in gear.

I tried it in Park/Neutral. The car would idle fine (with that line plugged off), but once I unplugged it, the engine would die. I hope that is normal.

Also, Is the headlight vacuum canister the big metal tube that looks like it's a front bumper?

Thanks everyone,

t78
 

NewVetter

Active member
Joined
Feb 21, 2006
Messages
35
Location
NH
Eric, others, yes, have same problem too on 82 just bought. Lights come on but doors no go up either via switch or the manual pull down under steering column. So those black vac hoses need to be in good shape, no cracks/leaks. Will look at em' and trim as you mentioned Eric and try other things posted here. Will report back progress. Just got the 82.... boy what fun cars these are. Have asked Qs here pre-buy and appreciate everyones input! Thanks so much, Regards, NewVetter
 

jdp6000

Well-known member
Joined
Aug 23, 2004
Messages
646
Location
Aurora, Ontario, Canada
Corvette
1982 CROSSFIRE
Easy to figure out if this is your problem. The vaccum supply is from the rear driverside on the manifold. Its just behind the throttle body. You will see a couple of hoses that go in to a round orfice and then a single hose that goes into the manfold. Unplug the orfice and plug the hose going into the manifold.

How are your brakes? Supply also comes from this area...different hose.

When it comes to the Crossfire you will get all your answers at http://www.crossfire.homeip.net/ Site is dedicated to our cars only.

Jim
 

NewVetter

Active member
Joined
Feb 21, 2006
Messages
35
Location
NH
Found vac hose under steer column was disconn from pull down switch. Reconnected, then found driver side light would pop up verrrrry slowly and pass. not at all. Still working on it, regards.
 

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