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Headlight vacuum help

Old Dec 3, 2010 | 10:41 AM
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Default Headlight vacuum help

Hey all,

I have a problem with my headlights, basically the tank wont hold vacuum!

All the hoses are new, the headlights are going up fine with engine running (although on of them is a bit slow).
When i turn the car on i need to let it "charge" a few seconds before i can open the headlights. If i close them and open straight ahead they dont come up, need a charging time in between!

Strange thing is that if i take off any of the 3 hoses going to the tank and put my finger on it i can feel the suction and it feels like there is some vacuum being created! Tried plugging all but the vacuum input hose and blow compressed air in the tank and it seems airtight!

Why wont it hold vacuum?

Cheers
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Old Dec 3, 2010 | 10:52 AM
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The tank has a leak or you could have a leak around one of the hoses to the tank.

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Old Dec 3, 2010 | 11:15 AM
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Make sure Your check valve is working, or Your vacum will bleed back to the engine right away on shut down.
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Old Dec 3, 2010 | 12:15 PM
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Originally Posted by Timsride
Make sure Your check valve is working, or Your vacum will bleed back to the engine right away on shut down.
Good point, never though about that?
Where is the check valve located? On the carb end?

C
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Old Dec 3, 2010 | 12:40 PM
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Originally Posted by Carlos840
Good point, never though about that?
Where is the check valve located? On the carb end?

C
It's metal and in the vacuum supply line off the manifold.

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Old Dec 3, 2010 | 01:00 PM
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Originally Posted by Easy Mike
It's metal and in the vacuum supply line off the manifold.

Well i dont even have that! My line goes straight from the manifold to a spliter, one tube goes to the dashboard switch i think and the second one goes to the tank!

That should be the problem then!

Just checked the part on willcox, mine is the same but in plastic, i guess for some reason my check valve must have been replaced by a spliter instead and thats why it doesnt hold vacuum!
Will replace it and see if it fixes the issue! Thanks guys.

Last edited by Carlos840; Dec 3, 2010 at 01:02 PM.
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Old Dec 3, 2010 | 01:38 PM
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Originally Posted by Carlos840
Good point, never though about that?
Where is the check valve located? On the carb end?

C
drivers side of the engine (usually) around the area of the distributor. should be a filter and the check valve right there.
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Old Dec 3, 2010 | 01:42 PM
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Originally Posted by srs244
drivers side of the engine (usually) around the area of the distributor. should be a filter and the check valve right there.
Yep, i visualise it, cant check it now, not in the same country as my car!
I do remember seeing something but i think i have a simple splitter instead of a check valve!
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Old Dec 3, 2010 | 01:48 PM
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It sounds like your vacuum tank is probably OK.
If putting the check valve in the line doesn't help I would suspect you have a leak somewhere else.
You can buy a hand operated vacuum pump pretty cheap at most auto part stores. Connect it to both sides of each headlight actuator and see if they not only operate, but hold a vacuum.
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Old Dec 3, 2010 | 02:00 PM
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Originally Posted by Carlos840
...Just checked the part on willcox, mine is the same but in plastic, i guess for some reason my check valve must have been replaced by a spliter instead and thats why it doesnt hold vacuum!...Will replace it and see if it fixes the issue! Thanks guys.
Check the assembly instruction manual (AIM), but I'm fairly certain you need both; one is white plastic; one is metal.

Someone correct me, but I believe the white plastic is a one way valve. It should not allow vacuum to bleed back from the tank side.


Last edited by Easy Mike; Dec 3, 2010 at 02:03 PM.
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Old Dec 3, 2010 | 02:11 PM
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Originally Posted by Easy Mike
Check the assembly instruction manual (AIM), but I'm fairly certain you need both; one is white plastic; one is metal.

Someone correct me, but I believe the white plastic is a one way valve. It should not allow vacuum to bleed back from the tank side.

According to the drawings i found there should be a plastic filter first, then the metal check valve!
I have the plastic filter, actually changed it recently but i dont have the check valve, just some dodgy splitter!
Didnt know i was meant to have a check valve...
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Old Dec 3, 2010 | 07:04 PM
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If one of your headlights is coming up slowly you might also need to rebuild the canister. A leaking canister will also allow vacuum to leak out.



Rick B.
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Old Dec 3, 2010 | 07:17 PM
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A good how to:
http://www.corvette-101.com/vacuum.htm
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