Vacuum System Shutdown Problem
Thread Starter
4th Gear
Joined: May 2010
Posts: 4
Likes: 0
Vacuum System Shutdown Problem
Anyone ever have a problem with the Wiper and Lights Vacuum system? When I shut the engine off the left headlight pops up and the wiper door opens.
Any idea what the cause might be?
Thanks
Pete
Any idea what the cause might be?
Thanks
Pete
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
The most likely problem is that the "check valve" in the vacuum feed line (round metal piece with one fitting on the 'input' side and two fittings on the 'output' side) has failed. Remove it from the vacuum lines and suck on the 'inlet' fitting while you hold a finger over one of the 'outlet' fittings. If the valve is working properly, you should not get any air through it when you suck on it. Try this with each of the output fittings. If there is any leakage, replace it. It is a good idea to replace the [white plastic] filter in that line while you are at it.
Thread Starter
4th Gear
Joined: May 2010
Posts: 4
Likes: 0
The most likely problem is that the "check valve" in the vacuum feed line (round metal piece with one fitting on the 'input' side and two fittings on the 'output' side) has failed. Remove it from the vacuum lines and suck on the 'inlet' fitting while you hold a finger over one of the 'outlet' fittings. If the valve is working properly, you should not get any air through it when you suck on it. Try this with each of the output fittings. If there is any leakage, replace it. It is a good idea to replace the [white plastic] filter in that line while you are at it.Thank you for the help. I know exactly the valve you are speaking of. I took it off before and "blew" through it rather than "sucking" on the inlet. I will try that.
However, there is nothing on the hose line between the "check valve" and the engine. I have a chart that shows there probably should be a filter on that line.....Do you agree for a 1970 Vette that a filter should be there and is it necessary function properly?
Thanks for the help.
Pete
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Yes the white thing is a filter,and yes it will function fine without it but you should have the filter in place to protect the check valve from intake fumes and soot.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
The filter is a separate device. From the manifold connection there is a short piece of hose, then the filter, then another short hose, then the check valve. From there, it heads toward the wiper door system, vacuum reservoir, and headlights. I am not absolutely sure about the purpose of the filter...whether it is to protect the check valve at engine start or shut-down, or whether it is to prevent any debris or degrading hose particles from getting into the intake manifold. Anyway, that's how the system is set up on early 70's cars.
Safety Car
Joined: Sep 2007
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From: Indy Indiana
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Burning Brakes
Joined: Jan 2006
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From: Clear Lake Shores Texas
2016 C3 of Year Finalist
I noticed that my car was missing the filter also so I ordered a new one as well as a new check valve. I have not installed the filter yet, but after I changed out the check valve the vacuum system no longer works - the headlight doors and wiper door both go up and stay up as soon as I start the engine. Everything worked fine previously, and worked fine again after I put the old valve back in. I am assuming the new valve is defective, unless the old valve was masking some other problem. Any other ideas?
Racer
Joined: Feb 2007
Posts: 271
Likes: 25
From: Buena Vista Colorado
The most likely problem is that the "check valve" in the vacuum feed line (round metal piece with one fitting on the 'input' side and two fittings on the 'output' side) has failed. Remove it from the vacuum lines and suck on the 'inlet' fitting while you hold a finger over one of the 'outlet' fittings. If the valve is working properly, you should not get any air through it when you suck on it. Try this with each of the output fittings.
Try to blow through the check valve on the single-ported side of the check valve and there should be NO flow through the check valve. That simulates manifold pressure returning to atmospheric pressure after shutting the engine down.
If the check valve fails either test, replace it.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
Whether you 'suck' and get airflow or you 'blow' and don't get airflow...it's all the same, except that with blowing through it, you never know if it is going to seal with vacuum applied. You just have to get your directions right.
Safety Car
Joined: Aug 2001
Posts: 4,883
Likes: 11
From: North Easton Mass
I noticed that my car was missing the filter also so I ordered a new one as well as a new check valve. I have not installed the filter yet, but after I changed out the check valve the vacuum system no longer works - the headlight doors and wiper door both go up and stay up as soon as I start the engine. Everything worked fine previously, and worked fine again after I put the old valve back in. I am assuming the new valve is defective, unless the old valve was masking some other problem. Any other ideas?
Rick B.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
I noticed that my car was missing the filter also so I ordered a new one as well as a new check valve. I have not installed the filter yet, but after I changed out the check valve the vacuum system no longer works - the headlight doors and wiper door both go up and stay up as soon as I start the engine. Everything worked fine previously, and worked fine again after I put the old valve back in. I am assuming the new valve is defective, unless the old valve was masking some other problem. Any other ideas?
