Vacuum Leak Somewhere
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
Vacuum Leak Somewhere
When I shut my car down, I can hear the loss of vacuum (hiss)...
I have no idea where it is coming from. Everything with regard to the vacuum system works.... so I can't narrow it down to a particular component.
Is there something I can use to pull vacuum from the main hose going to the manifold, so I can listen to where the hiss is coming from. Cant do it with motor one cause motor os too loud... the hiss goes away in a 1 second after shutdown so too short to find the hiss.
Not sure the hand vaccum pump will work, since I need a steady constant vacuum....
ideas?
I have no idea where it is coming from. Everything with regard to the vacuum system works.... so I can't narrow it down to a particular component.
Is there something I can use to pull vacuum from the main hose going to the manifold, so I can listen to where the hiss is coming from. Cant do it with motor one cause motor os too loud... the hiss goes away in a 1 second after shutdown so too short to find the hiss.
Not sure the hand vaccum pump will work, since I need a steady constant vacuum....
ideas?
Team Owner
Joined: Sep 2006
Posts: 31,270
Likes: 4,362
From: Westminster Maryland
Hi g1980,
Yes, a pump like a MityVac will provide enough vacuum to determine where the leak is.
In addition, the hand pump is silent so it'll be easier to determine where the slow leak is.
Regards,
Alan
Yes, a pump like a MityVac will provide enough vacuum to determine where the leak is.
In addition, the hand pump is silent so it'll be easier to determine where the slow leak is.
Regards,
Alan
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
Can you send me a link to the MityVac you are referring to? Thanks for your help.
Drifting
Joined: Jul 2006
Posts: 1,259
Likes: 154
From: Deplorableville Nebraska
In your case, it may be more efficient to work the opposite direction. To insure your hiss is coming from the headlight system, disconnect the hose coming off the manifold. Then using a short piece of hose, plug one end (a golf tee works), and connect the other to the manifold outlet. Start the engine which will energize the remaining vacuum systems on the car. Then turn the engine off.....Do you hear the same hiss? If so, it's something else. If not, it's the headlight vacuum system somewhere. Your next move is to connect the vacuum hose back up to the manifold, and disconnect the next component in line, which should be the filter. Plug the downstream end, and perform the test again. Next would be the check valve, etc on down the line. Continue down the vacuum hoses until you find the culprit.
Team Owner
Joined: Sep 2006
Posts: 31,270
Likes: 4,362
From: Westminster Maryland
Hi 1980,
You may want to try Dave's method first since it doesn't take any $.
Here's the Link to Mityvac.
Good Luck,
Regards,
Alan
http://www.mityvac.com
You may want to try Dave's method first since it doesn't take any $.
Here's the Link to Mityvac.
Good Luck,
Regards,
Alan
http://www.mityvac.com
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
Hi 1980,
You may want to try Dave's method first since it doesn't take any $.
Here's the Link to Mityvac.
Good Luck,
Regards,
Alan
http://www.mityvac.com
You may want to try Dave's method first since it doesn't take any $.
Here's the Link to Mityvac.
Good Luck,
Regards,
Alan
http://www.mityvac.com
When I disconnect the hose from the check valve to the reserve tank... and cap off the disconnected end on the check valve the hiss at engine shut down goes away.
I am almost thinking that there isn't a leak, and the check valve is bad.... so when I shut down the engine, the vacuum is able to escape and isn't kept in the system, which explains why I hear the hiss after I shut the engine down. Cheap part, so I'll check that out first. We'll see.
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Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
I am 99% sure at this point the the check valve is bad.... and the hiss at shut down I hear is the vacuum from the reserve tank and the rest of the system passing back through the bad check valve... once the manifold vacuum is gone because the engine is off.
Using "lung power" I was able to confirm the the check valve is allowing airflow in both directions.
So I really think I don't have a leak at all at this point, just a bad check valve.
I have a new check valve ordered, and when I get it, I'll know for sure if the hiss is eliminated.
Last edited by genuine1980; May 23, 2013 at 09:25 AM. Reason: e
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
Yes, and from what I can tell, I don't have leaks within them... everything works and seems to hold vacuum when I isolate the faulty check valve.
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
What are the chances the new check valve I got from Zip Corvette is no good?
I put the new check valve on, and indeed my hiss is gone... that was the culprit.
HOWEVER,
My lights and wiper door barely can open.... I took the check valve off and tested it with lung power.... it is very hard to suck air through it. Almost as if you need a certain amount of vacuum to just get the check valve to open.
The check valve does not let any air through backward, as expected. But should it be that hard for air to go through in the correct direction.
Thought?
Yes I am sure I was testing it in the right direction. :-)
I put the new check valve on, and indeed my hiss is gone... that was the culprit.
HOWEVER,
My lights and wiper door barely can open.... I took the check valve off and tested it with lung power.... it is very hard to suck air through it. Almost as if you need a certain amount of vacuum to just get the check valve to open.
The check valve does not let any air through backward, as expected. But should it be that hard for air to go through in the correct direction.
Thought?
Yes I am sure I was testing it in the right direction. :-)
Last edited by genuine1980; May 23, 2013 at 09:50 PM. Reason: e
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
NEW ISSUE NOW:
When the engine is at low RPM, which causes the less vacuum.... I assume this means I would have less vacuum in the system....
Anyway when the RPM goes very low, or when I first start the engine, the wiper door opens. And then it closes back up after the engine RPM raises to give sufficient vacuum to the system.
I don't know if there is a faulty/weak valve someplace, or if I have a vacuum leak someplace.
I don't know where I would have a leak, as I checked all the lines for leaks as best I could, listened for leak hissing, etc. In the process I found the check valve to be bad and replaced that.
Looking to be pointed in right direction to look for this new issue.
Could it be the Headlight/Wiper Door Vacuum Relay starting to go bad???
When the engine is at low RPM, which causes the less vacuum.... I assume this means I would have less vacuum in the system....
Anyway when the RPM goes very low, or when I first start the engine, the wiper door opens. And then it closes back up after the engine RPM raises to give sufficient vacuum to the system.
I don't know if there is a faulty/weak valve someplace, or if I have a vacuum leak someplace.
I don't know where I would have a leak, as I checked all the lines for leaks as best I could, listened for leak hissing, etc. In the process I found the check valve to be bad and replaced that.
Looking to be pointed in right direction to look for this new issue.
Could it be the Headlight/Wiper Door Vacuum Relay starting to go bad???
Drifting
Joined: Jul 2006
Posts: 1,259
Likes: 154
From: Deplorableville Nebraska
The issue in diagnosing vacuum leaks is that when you find and repair one vacuum leak, that kicks the can down the road. The next leaking component will show it's ugly head. If your relays and especially the wiper vacuum switch under the right side wiper blade are original, that's where you should look next.
The default position for the wiper door with NO control vacuum to the relay is in the up or open position. You need vacuum going from the relay to the actuator to close the door. If the vacuum control valve under the wiper is bad, the relay will never see control vacuum. That's where my money is.
The default position for the wiper door with NO control vacuum to the relay is in the up or open position. You need vacuum going from the relay to the actuator to close the door. If the vacuum control valve under the wiper is bad, the relay will never see control vacuum. That's where my money is.
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
The issue in diagnosing vacuum leaks is that when you find and repair one vacuum leak, that kicks the can down the road. The next leaking component will show it's ugly head. If your relays and especially the wiper vacuum switch under the right side wiper blade are original, that's where you should look next.
The default position for the wiper door with NO control vacuum to the relay is in the up or open position. You need vacuum going from the relay to the actuator to close the door. If the vacuum control valve under the wiper is bad, the relay will never see control vacuum. That's where my money is.
The default position for the wiper door with NO control vacuum to the relay is in the up or open position. You need vacuum going from the relay to the actuator to close the door. If the vacuum control valve under the wiper is bad, the relay will never see control vacuum. That's where my money is.
ALSO - Would engine RPM effect this... the door opens when first starting the engine, and if the RPM is too low for too long.
Last edited by genuine1980; Jun 4, 2013 at 04:36 PM. Reason: e
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
Wait... I think this is the part your thinking is bad.
Again... the door opens as described above. Does that make sense for this problem with this part? It opens as expected using the switch or overide switch... but opens by itself when first starting engine or low RPM for too long.
Again... the door opens as described above. Does that make sense for this problem with this part? It opens as expected using the switch or overide switch... but opens by itself when first starting engine or low RPM for too long.
Last edited by genuine1980; Jun 4, 2013 at 04:42 PM. Reason: e
Drifting
Joined: Jul 2006
Posts: 1,259
Likes: 154
From: Deplorableville Nebraska
That's a relay. It sends vacuum to the wiper door actuator. If it has no control vacuum (the small fitting on top), it sends vacuum to open the door. If it has control vacuum, it sends vacuum to the other side of the actuator to close the door.
What sends the control vacuum signal is the wiper door vacuum valve. It sits about 2 inches away from the passenger side wiper post, under the wiper arm. I don't have a picture right now, but it's about one third the size of the relay, and will have 3 small hoses coming out of it. You need to have the wiper door open or the wiper grill to see it.
What sends the control vacuum signal is the wiper door vacuum valve. It sits about 2 inches away from the passenger side wiper post, under the wiper arm. I don't have a picture right now, but it's about one third the size of the relay, and will have 3 small hoses coming out of it. You need to have the wiper door open or the wiper grill to see it.
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
Ok... now does it make sense that the door opens as it is supposed to when using the switch in the car and if I use the over ride switch... and stays closed any other time....
Except for when I first start the car, and when the engine RPM falls too low for too long.
This part being faulty is what is making the door open when it shouldn't in only those two situations?
The part is cheap, so I might just get it anyway to see...
Except for when I first start the car, and when the engine RPM falls too low for too long.
This part being faulty is what is making the door open when it shouldn't in only those two situations?
The part is cheap, so I might just get it anyway to see...
Drifting
Joined: Jul 2006
Posts: 1,259
Likes: 154
From: Deplorableville Nebraska
Normal vacuum would likely make the valve behave normally, in other words, have enough vacuum to keep control to the relay. At reduced vacuum, the leaky valve would not leave enough vacuum in the circuit to actuate the relay, and thus close the door.
You can test the valve in your car. Remove the wiper door. Actuate the wipers and stop the travel somewhere along the top of the travel. IGNORE the top hose on the valve. Disconnect the middle hose on the valve. Next, disconnect and plug the small top control hose on the wiper relay. Find a short length of control hose, and connect to the middle outlet on the valve. Depress the top button on the valve, and you should be able to:
1 - Not be able to blow through the middle hose, (no leaks)
2 - Encounter vacuum when sucking on the middle hose, (actuating the relay )
You can test the valve in your car. Remove the wiper door. Actuate the wipers and stop the travel somewhere along the top of the travel. IGNORE the top hose on the valve. Disconnect the middle hose on the valve. Next, disconnect and plug the small top control hose on the wiper relay. Find a short length of control hose, and connect to the middle outlet on the valve. Depress the top button on the valve, and you should be able to:
1 - Not be able to blow through the middle hose, (no leaks)
2 - Encounter vacuum when sucking on the middle hose, (actuating the relay )