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Vaccum gauge?

Is it worth it, can it really help to diagnose alot of the problems on my 944 and if so what about mounting on an early car? any ideas or advice?

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'84 944na -- Sold
'84 944na -- Sold
'85 944na, -- Sold
Old 10-16-2003, 05:22 PM
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I use one to gauge general engine condition. It can tell you in a second if you have blown a head gasket or have bad valve guides. I take one with me when looking at a potential buy. I used to use it to set my distributor advance, but thats a lost art now. I wouldn't mount one up, but there is a handy vaccum port on the throttle body for a quick reading.
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'87 924S , sold.
'99 Subaru O/B, 62K on first timing belt. Could have gone another 40K.
Old 10-17-2003, 06:33 AM
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It's true, if you know what to look for a vacuum gage can be used to diagnose any number of problems from sticking valves to intake leaks.

As a point of reference though, don't use either port on the throttle body.

The first port is above the throttle plate and only has a very small vacuum (about 5" Hg on both of my cars), and this vacuum is only present just as the throttle plate comes off of its seat. This "momentary" vacuum is used to control the purge valves for the fuel tank and charcoal cannister.

The second port on the throttle body is just below the throttle plate and will not show actual manifold vacuum. I've seen as much as 5" Hg difference between vacuum on this port and actual manifold vacuum. This port supplies vacuum to the Fuel Pressure Regulator, Fuel Pressure Damper, and the charcoal cannister/fuel tank purge valves.

The best place to check manifold vacuum is where the small line comes off of the check valve at the brake booster.
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Cliff Hipsher
'87 944 India Red
'86 951 Kalahari Metallic
Old 10-17-2003, 08:47 PM
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Hmmm, I was getting a good reading from the second port, but I'll check out the other one. I have to compensate for altitude, so a loss of 5" is normal. One inch Hg per 1000' if I remember right. Most of the diagnostic stuff I do with vaccum is more concerned with how steady the needle is. But bad timing and vaccum leaks are diagnosed with with the actual reading.
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'87 924S , sold.
'99 Subaru O/B, 62K on first timing belt. Could have gone another 40K.
Old 10-18-2003, 08:01 AM
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hmm, okay, so for about $59 i think it might be worth it, kinda cheap insurance or a way to figure out what i can do to make the car run better
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'84 944na -- Sold
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Old 10-18-2003, 09:22 AM
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vott does ziss do?
 
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which gauge do you guys recommend
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Old 10-18-2003, 12:14 PM
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$59?? I know I got mine long ago, but I don't think it should be that much. It's also so old I don't know who made it. I'm sure it was the cheapest I could find. It has 0-30 inches Hg on one side and 0-10 psi on the pressure side (for fuel pump testing).
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'87 924S , sold.
'99 Subaru O/B, 62K on first timing belt. Could have gone another 40K.
Old 10-19-2003, 09:49 AM
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hmm, well where can i get a god one? i found the $59 kit here: http://www.9xauto.com/944vac.html
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Old 10-19-2003, 12:44 PM
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Ok, $59 for a panel-quality gauge sounds better. Mine is a hand-held unit with a piece of rubber hose attached. I think I got it from Sears. Here is one that is close for $24:

http://www.partsamerica.com/PartDetails.asp?SourceArea=SHOP&SourcePage=SEARCHRESULTS&MfrCode=EQU&MfrPartNumber=3620&CategoryCode=3342F
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'87 924S , sold.
'99 Subaru O/B, 62K on first timing belt. Could have gone another 40K.
Old 10-20-2003, 06:57 AM
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try harbor freight. They have cheap stuff and it works. I got all my guages from em and work just as good as the more expensive.
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Old 10-20-2003, 07:04 AM
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You don't need a panel mounted gage, you need a gage for your tool box. Go to Pep Boys, or where ever and get a simle gage. Save the $30.00 or so for your next oil change.
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Cliff Hipsher
'87 944 India Red
'86 951 Kalahari Metallic
Old 10-20-2003, 07:06 AM
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alright thanks you guys, the other question is is there a list of how to use it and readings and such? like a little manual or a book of some sort?
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Old 10-20-2003, 08:02 AM
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I use one included in the troubleshooting chapter of an old Chilton's manual. If you don't have one I can try to scan it and send it to you. Here are a few sites I found are just as good:

http://www3.bc.sympatico.ca/BOBLEVIS/vacugage.html

http://autorepair.about.com/library/weekly/aa112401a.htm

http://www.earlycuda.org/tech/vacuum2.htm
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'87 924S , sold.
'99 Subaru O/B, 62K on first timing belt. Could have gone another 40K.
Old 10-20-2003, 01:38 PM
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vott does ziss do?
 
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if anyone has a preference for one gauge or the other, let us know.

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Old 10-20-2003, 07:01 PM
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