VACUUM LEAK???
Thread Starter
Safety Car
Joined: Mar 2002
Posts: 4,411
Likes: 1
From: Okeechobee Florida
VACUUM LEAK???
i have to shut off my lights BEFORE i turn the car off or else they will not go down...turn em off while running/no problem...do i have a vac leak somewhere??
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Re: VACUUM LEAK??? (SIGNGUY)
Most of the time, the problem with not holding vacuum is going to be in the main supply checkvalve or the actuator control valve(s) are leaking past the seals. A very common situation with C3s. You can test the system by just disconnecting the operating hose from the valve(s) and connect a vacuum gauge to see if the leak is in the tank/hose/checkvalve or in the control valves. You can easily diagnose the checkvalve by removing it and trying to blow into both hose ends. If you can blow in one direction, but not the other, the valve is O.K.
Team Owner
Joined: Jul 1999
Posts: 26,545
Likes: 46
From: Huntersville NC
Re: VACUUM LEAK??? (SIGNGUY)
Isnt it more likely that there is a leak in the vacuum "storage" tank or whatever that thing is called? You say the headlights go up and down no problem when the engine is running, right? When you shut the engine off, there is a tank that is supposed to hold enough vacuum to open/shut the headlights once, maybe twice. I think the tank is actually supposed to hold vacuum overnight, so in theory you could raise your headlights in the morning before turning the car on. Very common for these tanks to not hold a vacuum. I couldnt find a noticeable leak on mine, yet it didnt seem to hold a vacuum, ie I couldnt move the headlights with the engine off. I bypassed the tank to see if it made the engine run any different - no difference. MJ
hmmm... I see what Gerry is saying, and in fact in my case the tank might be ok but could be losing the vacuum after shutoff thru the other things he mentioned.
[Modified by MNJack, 8:48 PM 5/6/2002]
hmmm... I see what Gerry is saying, and in fact in my case the tank might be ok but could be losing the vacuum after shutoff thru the other things he mentioned.
[Modified by MNJack, 8:48 PM 5/6/2002]
Thread Starter
Safety Car
Joined: Mar 2002
Posts: 4,411
Likes: 1
From: Okeechobee Florida
Re: VACUUM LEAK??? (MNJack)
my headlights go up and down "OK"
(not great...slow...with one lagging behind the other) when the engine is running...but not at all when engine is off.
i was under the same understanding that you are about the tank doing what you said etc...
BTW...are the heater-a/c controls operated by vacuum as well?
(not great...slow...with one lagging behind the other) when the engine is running...but not at all when engine is off.
i was under the same understanding that you are about the tank doing what you said etc...
BTW...are the heater-a/c controls operated by vacuum as well?
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Re: VACUUM LEAK??? (SIGNGUY)
First, the vacuum check valve is in the main supply line that is connected to the intake. It is a disc about 1" in diameter and will have two hose connections on one end and one hose connection on the other end. It should be very near the manifold. You will also see a white plastic disc about the same size on the main line. That is a filter.
Check the simple things, like the valve, first. If the valve checks fine, then your problem is likely in the actuator valves or a vacuum hose gone bad. If the actuator valves leak, they will cause sluggish headlight operation and will bleed vacuum once the engine is turned off. It could also be in the headlight vacuum motors since these rely on a vacuum on one side of the chamber that has a flexible seal. If the seal is leaking, the headlights will be slow to open (or is that close...can't remember which chamber has the shaft seal). The way to test all of these things is with a vacuum pump. It's really not that hard to find out what component, including the storage tank, is causing your problem. And, yes, the HVAC is controlled by vacuum.
Check the simple things, like the valve, first. If the valve checks fine, then your problem is likely in the actuator valves or a vacuum hose gone bad. If the actuator valves leak, they will cause sluggish headlight operation and will bleed vacuum once the engine is turned off. It could also be in the headlight vacuum motors since these rely on a vacuum on one side of the chamber that has a flexible seal. If the seal is leaking, the headlights will be slow to open (or is that close...can't remember which chamber has the shaft seal). The way to test all of these things is with a vacuum pump. It's really not that hard to find out what component, including the storage tank, is causing your problem. And, yes, the HVAC is controlled by vacuum.
Pro
Joined: Aug 1999
Posts: 749
Likes: 0
From: Perth,Western Australia,Australia
Re: VACUUM LEAK??? (SIGNGUY)
http://www.corvette-101.com/
I found the above website last night,very informative.pictures of the components,as well as a fault finding description.Just click on vacuum trouble.
I found the above website last night,very informative.pictures of the components,as well as a fault finding description.Just click on vacuum trouble.
Thread Starter
Safety Car
Joined: Mar 2002
Posts: 4,411
Likes: 1
From: Okeechobee Florida
Re: VACUUM LEAK??? (Fleetwood)
BINGO!!! this is all any of us need...we should ALL have this....i printed it out and it will go right in my toolbox (AFTER i follow it to the T)
THANX A LOT!
THANX A LOT!
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