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Old 06-02-2016, 10:52 AM   #1
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DIY cheap vaccum gauge inWC

I guys!

As you may have red, I have problems after an AOS swap...
I wanted to make sure that the AOS was bad before doing anything.

I tried to read crankcase vacuum with a regular vacuum gauge... but the vacuum is so little that the gauge couldn't read anything...

According to pelican parts, the spec is 4 to 7"WC at idle, that's ~0.3inHg... no good for a regular gauge.

Since I'm cheap and I had some time (took 10min actually), I went to home depot to make my own vacuum gauge...

A water column gauge! That's about the only thing I like with american units, "inches of water" are actually inches of water!

Here is what you need (everything came from Home Depot, for 11$ total):

I used 20' of clear hose (it's 3/16" ID), two 1/4" barbed shutoff valves, and a 1-5/8" rubber stopper (for sinks). Plus the cheapest HDX glue.
You'll also need a piece of carboard and small sipties.






I don't think I need to explain what I did, it's pretty simple

With the shutoff valves I can freeze the reading pretty easily. since the tube is narrow, the surface tension keeps the water from sloshing around when the valves are closed.

The most difficult part is to put the right amount of water inside (I put too much), the level at rest should be in the middle of the column.

You can't see it on the pictures but I drew the graduations behind the hose and you can easily read the level through it!

To use it it's simple, hook it up to the oil cap (the rubber stopper that I used is almost too small, you'll have to leave the funnel inside and seal everything with a few drops of oil.)
Open the two valves.
You'll see the level drop on one side and rise on the other, measure the distance it dropped or rose and multiply it by 2 to get the actual water column height!
The "gauge" needs to be as close to vertical as you can.

On my car, I red a bit more that 1.5" of water column on one side, time 2, that's about 3"WC... I might have a vacuum leak somewhere.

It's not the most accurate tool and its affected by temperature... but it can give you an idea of what's going on quickly for a few $ (most of use already have zipties, cardboard and glue!)

I hope this will help some of you

Ben
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Old 06-02-2016, 12:19 PM   #2
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Very clever. Its easy to forget how simple some things really are and that you don't need an expensive specialized tool for every little thing.

I think a lot of folks could have used such a device when dealing with rough/fluctuating idles, AOS issues and O2 sensor codes.

So what does 4-7 Water Column inches translate to in Beer Inches?
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Old 06-02-2016, 12:30 PM   #3
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I can't tell you about beer, I only drink those! (Density of beer is about 1.1 the density of water google says! )

It's exactly what I'm going through right now, rough idle, almost no engine braking, and P1128 P1130 codes!
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Old 06-06-2016, 11:07 PM   #4
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Yes you are right Ben.
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Old 06-07-2016, 05:48 AM   #5
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I found the problem with a leak tester, it is the long crankcase vent hose that connects behind the AOS.
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