Headlight Vacuum system questions....
Thread Starter
Instructor
Joined: May 2005
Posts: 245
Likes: 5
From: Layton, UT
Headlight Vacuum system questions....
I've been fighting with my headlight system since i bought my car. Working on it today i found that the vacuum tank isn't holding vacuum- so i just completely eliminated it and put a tee in the hose that runs to it- then added two hoses straight to the yellow relay ports. Makes sense?? Okay- well they are working a little better now- they seem to open okay- but they struggle closing. And i just found out on the way home- that if i floor it- the headlights pop up. Does anyone know where i can find a diagram of how much vacuum is supposed to be running to the relays. I tested the small hose and it looks like its pulling about 2.5 to each relay. Anyone know if thats low, or normal? Any other ideas as to why the headlights pop up when i give it hard gas- or why they don't like to close very smoothly.
Burning Brakes
Joined: Jun 2002
Posts: 837
Likes: 3
From: Texas
With a hand held vacuum pump and this troubleshooting guide you should be able to find your problems in short order.
http://209.183.231.72/corvette-101/vacuum.htm
From the sound of it you may need to replace the check valve, but the troubleshooting guide will show you any other components that need a rebuild or replacement. The system is actually pretty reliable once everything is in working order.
Hope this helps.
http://209.183.231.72/corvette-101/vacuum.htm
From the sound of it you may need to replace the check valve, but the troubleshooting guide will show you any other components that need a rebuild or replacement. The system is actually pretty reliable once everything is in working order.
Hope this helps.
Thread Starter
Instructor
Joined: May 2005
Posts: 245
Likes: 5
From: Layton, UT
I have that trouble shooting guide- but my main question is how much vacuum is the motor supposed to pull? And how much should be pulling at the top connection of the relay? I hooked a vacuum pump to the motor and it was bouncing around 40 inches of vacuum. I then checked the small hose right before it goes into the relays and it's pulling around 2.5 to each relay. Is that enough to properly operate the system?
Instructor
Joined: Jan 2005
Posts: 159
Likes: 0
From: Chardon Ohio
The vacuum at the relays should be equal or a little less than what you get at the check valve. A large reduction in vacuum in the yellow line into the relays indicates a leak in the system somewhere.
Racer
Joined: Sep 2001
Posts: 397
Likes: 1
From: CORTLANDT MANOR NY
If you eliminate the vaccum tank your system will not work properly because as soon as you shut the engine you will lose vacum and the wiper doors will open. When running the headlights will pop up and down as vacum changes. At WOT there is little or no vaccum to hold the headlights up. The vacum tank is an intricate part of the system so repair it or nothing will work properly.
Thread Starter
Instructor
Joined: May 2005
Posts: 245
Likes: 5
From: Layton, UT
I've been running the system without the vac tank for two days now- and i haven't had any issues with the headlights. They pop up and stay up when i turn them on- and they do drop when i turn them off. I do believe i probably have a leak somewhere around the intake and thats why i don't have enough vac overall in the system. As far as wiper door- i don't even know what you're refering to- unless mine was removed before i purchased the car or something. Mine is an 80- did they have wiper doors in that year- of so- does someone have a pic of them- because i don't think my car has them.
Melting Slicks
Joined: May 2003
Posts: 2,253
Likes: 1
From: Rochester Kent
Originally Posted by dyanisis2
I've been running the system without the vac tank for two days now- and i haven't had any issues with the headlights. They pop up and stay up when i turn them on- and they do drop when i turn them off. I do believe i probably have a leak somewhere around the intake and thats why i don't have enough vac overall in the system. As far as wiper door- i don't even know what you're refering to- unless mine was removed before i purchased the car or something. Mine is an 80- did they have wiper doors in that year- of so- does someone have a pic of them- because i don't think my car has them.
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Drifting
Joined: Jun 2005
Posts: 1,950
Likes: 498
From: Chino Hills CA
The vacuum tank's job is to just store enough vacuum to open and close the headlights a couple of times with the engine off. The headlights will stay up or down even if there are no vacuum lines hooked up or even an actuator attached. The geometry of the design and the springs will see to that. The headlight system will work fine without a vacuum tank except that they will be a little slow and uneven, but they will work. (the constant vacuum built up in the tank will make them work better.) Your engine pulls the most vacuum at idle, so that's when the system will work the best, unless you run a cam with a lot of overlap. Deceleration also pulls a lot of vacuum. Best answer is to get your tank filled and reinstall it. If you don't have a good manual, most of the free parts catalogs you get, have pretty good vacuum diagrams, albeit a bit small. Take a digital picture or scan one and blow it up. Who says nothing's free these days...
Drifting
Joined: Dec 2004
Posts: 1,345
Likes: 3
Originally Posted by BUGGSY1970
If you eliminate the vaccum tank your system will not work properly because as soon as you shut the engine you will lose vacum and the wiper doors will open. When running the headlights will pop up and down as vacum changes. At WOT there is little or no vaccum to hold the headlights up. The vacum tank is an intricate part of the system so repair it or nothing will work properly.
Drifting
Joined: Jun 2005
Posts: 1,950
Likes: 498
From: Chino Hills CA
The vacuum pulls the headlights down, not holds them up, and we're talking about the vacuum to the relay, not the actuators. The sytem is designed so that in vacuum failure mode, you can easily raise the headlights by hand and be able to drive your vette at night. It is much more diificult to pull them down by hand, but far from impossible. The springs will hold them up or down in either case. The light switch turns vacuum from the source to the relay on or off. Lights on, no vacuum, lights off, vacuum to the relay. When the relay receives no vacuum from the switch, it sends vacuum to the open side of the actuator. When the relay receives vacuum from the switch, it sends vacuum to the close side of the actuator. Very clever really, the wiper door works the same way.
Burning Brakes
Joined: Jun 2002
Posts: 837
Likes: 3
From: Texas
The vacuum diagram from the 101 site can be enlarged for full page printing.
From the top of the 101 page...
"Click on the vacuum system graphic below to enlarge for printing or to save to your hard drive"
It's nice to have that diagram and the guide with you at the car when going through the system.
From the top of the 101 page...
"Click on the vacuum system graphic below to enlarge for printing or to save to your hard drive"
It's nice to have that diagram and the guide with you at the car when going through the system.
