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kkjellquist
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Joined: June 04, 2013
Posts: 752
Location: Asheville, NC
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 Posted: Thu Jul 31, 2014 7:34 am Post subject: Vacuum Gauge Questions & Installs |
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I can't lie, I like gauges. Lots of people do.
I'd also like to know more about vacuum gauges and reading them. Think I have a vacuum leak and will test w/ WD40, etc but I like the idea of a gauge.
I have an empty spot in a VDO pod and would maybe consider a dash mount. Anyone want to speak to this install?
At the very least I would like to buy a gauge and do some readings and learn more.
Anyone have pics, thoughts, tutorials, etc?
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Turtel - http://www.thesamba.com/vw/forum/viewtopic.php?t=561195
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SGKent 
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Joined: October 30, 2007
Posts: 42420
Location: at the beach
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| Posted: Thu Jul 31, 2014 7:50 am Post subject: |
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IMHO, it will simply tell you how many inches of vacuum the engine is pulling. A car engine is not constant speed engine like an aircraft so it isn't going to help you a lot - especially when you have a long run of hose to the front which will buffer any fluctuations that might be useful.
Other options that are more useful in this order:
Oil Pressure
Oil Temp
Head Temp
Voltage
O2 sensor
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aeromech
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Joined: January 24, 2006
Posts: 17615
Location: San Diego, California
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| Posted: Thu Jul 31, 2014 7:54 am Post subject: |
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I'm not an expert but this might help.
http://www.international-auto.com/fiat-lancia-tips...gauges.cfm
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kkjellquist
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Joined: June 04, 2013
Posts: 752
Location: Asheville, NC
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| Posted: Thu Jul 31, 2014 8:39 am Post subject: |
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| SGKent wrote: |
especially when you have a long run of hose to the front which will buffer any fluctuations that might be useful.
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Thanks...I was wondering if you had to run the hose all the way of if there was a sender unit. Probably won't do a dash install then.
Looks like I'll buy an inexpensive gauge and just use it for troubleshooting as needed.
_________________
1977 Sage Green Deluxe Campmobile - "Turtel"
(1978 2L FI, Pertronix, Hydraulic Lifters)
Turtel - http://www.thesamba.com/vw/forum/viewtopic.php?t=561195
Pisgah Bus Rally - New Year's Day
http://pisgahbusrally.blogspot.com/ |
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germansupplyscott
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Joined: May 22, 2004
Posts: 7245
Location: toronto
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| Posted: Thu Jul 31, 2014 8:45 am Post subject: |
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i have one dash-mounted. you use a length of small diameter flexible air hose, it's no different than running a wire. it tees into the plenum. it's a useful gauge.
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Lionhart94010
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Joined: January 04, 2005
Posts: 1418
Location: SF Bay Area / Silicon Valley / So Cal
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| Posted: Thu Jul 31, 2014 8:51 am Post subject: |
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Good idia:0) You won’t believe how many things you can determine just by connecting a vacuum gauge to an engine :0)
Checking the engines intake manifold vacuum
(See URL for how to interpret a vacuum gauge reading)
Helps Detect:
Small Vacuum leaks(intake system)-
Worn Rings-
Sticking Valves-
Burnt or Leaking Valves-
Worn Valve Guides-
Week Valve springs-
Late Valve Timing-
Retarded ignition Timing-
Major Intake Leak-
Blown Head Gasket-
Clogged Exhaust System-
Improperly adjusted idle mixture-
http://www.secondchancegarage.com/public/186.cfm
http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm (Not VW but good explanations)
http://www.motor.com/article.asp?article_ID=457
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VW technical information sights
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http://bobhooversblog.blogspot.com/ - www.aircooled.net/gnrlsite/resource/articles.htm |
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Wildthings
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Joined: March 13, 2005
Posts: 52296
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| Posted: Thu Jul 31, 2014 9:02 am Post subject: |
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A tend to set up a vacuum gauge as a temporary measure when I first am setting up an engine and then end up leaving it hooked up for years.
The right diameter hose helps. Not too big or too tiny, either will damp the vacuum signal quite a bit. |
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kreemoweet
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Joined: March 13, 2008
Posts: 4089
Location: Seattle, WA
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| Posted: Thu Jul 31, 2014 9:47 am Post subject: |
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The easiest way to set up a vac gauge is to modify the vacuum line going to the brake servo to include a tee, in the area just to the rear of the servo.
You will also have to move the check valve so it's between the tee and the booster.
I did that, and used 1/4 in. (OD) flexible copper tubing from the tee to the gauge. You could also probably use the nylon/PEX water tubing typically used to feed refrigerator
ice makers. My vac gauge did not have a restriction orifice in it, and far from damping the vacuum signal from the intake manifold, I had to install
a needle valve with the needle barely open, in order to prevent the violent vacuum fluctuations that exist in the manifold from causing excessive
needle vibration. The gauge response to moving the throttle pedal is pretty much instantaneous.
I'm not sure I could say that gauge has been terribly useful, but I can think of some situations where it would be handy for diagnosis.
I would take all the interpretation charts you see posted with a large handful of salt, each engine will have it's own normal vacuum signature, and the
numbers simply cannot be given an unambiguous meaning.
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Tcash
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Joined: July 20, 2011
Posts: 12846
Location: San Jose, California, USA
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| Posted: Thu Jul 31, 2014 9:58 am Post subject: |
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A vacuum gauge is a great idea. Vacuum test can tell you more about your engine than any other gauge . Vacuum gauges are the most misunderstood and under utilized gauge. The problem lies in interpreting the charts available. But with the advent of Youtube videos, you can see real time readings.
Vacuum lag would be negligible.
Examples of conditions that vacuum gauges can show.
Engine is normal
Sticky valve
Week or broken valve springs
Valves out of adjustment
Burnt valves
Flat cam
Worn rings and cylinder
Combustion chamber leak
Unbalanced carbs
Improper spark plug gap
Spark plug failure
Poor valve seating
Leak at manifold or carb to manifold
Restricted exhaust
Restricted intake - dirty air cleaner
Undersized carb
Balance test
Vacuum leaks
Adjustments you can make.
Ignition timing
Fuel mixture
So bang for buck, you get the most out of a vacuum gauge.
Good Luck
Tcash
Vacuum Charts |
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Tcash
Samba Member
Joined: July 20, 2011
Posts: 12846
Location: San Jose, California, USA
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| Posted: Thu Jul 31, 2014 9:59 am Post subject: |
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double
Last edited by Tcash on Thu Jul 31, 2014 6:53 pm; edited 1 time in total |
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kkjellquist
Samba Member
Joined: June 04, 2013
Posts: 752
Location: Asheville, NC
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| Posted: Thu Jul 31, 2014 10:46 am Post subject: |
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| kreemoweet wrote: |
The easiest way to set up a vac gauge is to modify the vacuum line going to the brake servo to include a tee, in the area just to the rear of the servo.
You will also have to move the check valve so it's between the tee and the booster.
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So put the T in the blue circle and move the check valve to the red circle?
VacuumHoses1
_________________
1977 Sage Green Deluxe Campmobile - "Turtel"
(1978 2L FI, Pertronix, Hydraulic Lifters)
Turtel - http://www.thesamba.com/vw/forum/viewtopic.php?t=561195
Pisgah Bus Rally - New Year's Day
http://pisgahbusrally.blogspot.com/ |
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Tcash
Samba Member
Joined: July 20, 2011
Posts: 12846
Location: San Jose, California, USA
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| Posted: Thu Jul 31, 2014 11:14 am Post subject: |
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| kkjellquist wrote: |
| kreemoweet wrote: |
The easiest way to set up a vac gauge is to modify the vacuum line going to the brake servo to include a tee, in the area just to the rear of the servo.
You will also have to move the check valve so it's between the tee and the booster.
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So put the T in the blue circle and move the check valve to the red circle?
VacuumHoses1 |
The "T" needs to be on the Red circle side of the check valve. |
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Jeff Geisen
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Joined: December 21, 2004
Posts: 1930
Location: N.W. Georgia
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| Posted: Thu Jul 31, 2014 12:04 pm Post subject: |
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Tap the same line at your brake booster for a permanent mount, best and most informative accessory gauge you can have, it'll diagnose a plethora of engine problems. This is what shops used back in the day when our buses were new, and electronics had not yet proliferated.
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 42420
Location: at the beach
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| Posted: Thu Jul 31, 2014 12:27 pm Post subject: |
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| Tcash wrote: |
A vacuum gauge is a great idea. Vacuum test can tell you more about your engine than any other gauge . Vacuum gauges are the most misunderstood and under utilized gauge. The problem lies in interpreting the charts available. But with the advent of Youtube videos, you can see real time readings.
Vacuum lag would be negligible.
Examples of conditions that vacuum gauges can show.
Engine is normal
Sticky valve
Week or broken valve springs
Valves out of adjustment
Burnt valves
Flat cam
Worn rings and cylinder
Combustion chamber leak
Unbalanced carbs
Improper spark plug gap
Spark plug failure
Poor valve seating
Leak at manifold or carb to manifold
Restricted exhaust
Restricted intake - dirty air cleaner
Undersized carb
Balance test
Vacuum leaks
Adjustments you can make.
Ignition timing
Fuel mixture
So bang for buck, you get the most out of a vacuum gauge.
Vacuum Charts
Good Luck
Tcash |
Totally disagree. It is a tuning tool and not a monitoring tool. To use it you properly have to watch it constantly for small changes. If you want that level of monitoring on a 40 year old car then set up electronic gauges that download into a file on a laptop where you can look over the results when you are not driving. I am sick and tired of dodging people whose heads are down inside their cars looking at some gauge, gps, text messaging or Lord knows what. You can glance at the gauges I mentioned. You cannot glance at a vacuum gauge and get anything out of it meaningful.
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kreemoweet
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Joined: March 13, 2008
Posts: 4089
Location: Seattle, WA
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| Posted: Thu Jul 31, 2014 5:39 pm Post subject: |
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| kkjellquist wrote: |
| So put the T in the blue circle . . . |
| kreemoweet wrote: |
| . . . in the area just to the rear of the servo. |
The servo is mounted on the front axle beam. At the other end of the bus.
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'68 bug: seized by the authorities
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Tcash
Samba Member
Joined: July 20, 2011
Posts: 12846
Location: San Jose, California, USA
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| Posted: Thu Jul 31, 2014 7:55 pm Post subject: Brake Booster Circuit |
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If you "T" in to the red side you will be able get vacuum readings. But do to the check valve you will not be able to perform the throttle snap test.
On the other hand you will be able to test your booster, hoses and check valve, every time you shut off the engine. The gauge will show the vacuum held in the booster circuit.
Good Luck |
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RhinoVonRiesenberger
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Joined: August 08, 2014
Posts: 5
Location: Alpharetta, Georgia
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| Posted: Mon Aug 11, 2014 3:53 pm Post subject: Brake Booster Circuit |
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| Tcash, where can I find the book that you pulled this diagram from? I feel like I have looked everywhere but no where can I find such a detailed diagram such as the one above. Thanks! |
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Tcash
Samba Member
Joined: July 20, 2011
Posts: 12846
Location: San Jose, California, USA
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| Posted: Mon Aug 11, 2014 6:19 pm Post subject: Re: Brake Booster Circuit |
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| RhinoVonRiesenberger wrote: |
| Tcash, where can I find the book that you pulled this diagram from? I feel like I have looked everywhere but no where can I find such a detailed diagram such as the one above. Thanks! |
Thanks to jerseylooker.
http://www.jerseylooker.com/FicheDump/EarlyBaywindow/EarlyBay-Main.html |
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Ampdub
Samba Member
Joined: August 16, 2008
Posts: 2
Location: Brisbane, Australia
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| Posted: Fri Oct 03, 2014 7:25 pm Post subject: |
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| Where does the line from the from of the booster go? outlet on line 65 |
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kreemoweet
Samba Member
Joined: March 13, 2008
Posts: 4089
Location: Seattle, WA
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| Posted: Fri Oct 03, 2014 9:24 pm Post subject: |
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That's a makeup air line. It connects to a steel tube that goes into the
wheel well and then up into the B pillar, where, hopefully, there will
exist an ample supply of clean, dry, air.
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