Inexpensive Vacuum Test Tool & Brake Bleeder

[GAHorn]

My instrument panel is partially disassembled while I R&R my AN Horizon (Aircraft Quality Instruments in Wichita overhauled it for me)...and I wanted to test the accuracy of my suction gauge, and also wanted to test the system for leak-down with the gyro removed.

I found this little tool at the chineese store and it was compared to a known-accurate suction gauge...then used to draw a vacuum on my aircraft system. It worked out really well for a $29 cheap tool (on sale). It is capable of creating from 0 to 25 inches of vacuum and was surprisingly accurate.
It is actually intended to bleed brake systems...and I suspect it'd also do a good job if used on the aircraft by drawing hyd fluid up thru the calipers with vacuum applied from the top of the master cylinders. Certainly worked quick/easy to check integrity of my suction system tho'.
Squeezing the handles pulls a piston thru the brass cylinder thereby creating a suction at the hose-barb fitting. The gauge measures the amount of vacuum drawn. The cylinder has a small schrader-type needle-valve on the underneath side, so it will hold the vacuum until you press the schrader for relief.

Thought I'd pass along the tip:

vacuum pump tester.jpg

[blueldr]

I think brake bleeding is easier done from the bottom up using a Plews (pump) type oil can and a short piece of clear vinyl tubing to watch for air bubbles.

[GAHorn]

I think brake bleeding is easier done from the bottom up using a Plews (pump) type oil can and a short piece of clear vinyl tubing to watch for air bubbles.

Yes, that is a valuable method... The problem with it however, is that air can be easily introduced if the Plews pump runs low on fluid, and the master cylinders can easily be over-filled creating a mess.

Another method for do-it-yourselfers is to convert an old 20 lb freon tank to a pressure pot and brass fittings from the hardware store.

A REALLY SIMPLE brake tool you can make yourself....is to buy a cheap garden pump-up sprayer.....typically less than $10 at ACE/True-Value.... Pour Mil 5606/Hyd-Fluid into it...pump it up...and, removing the spray nozzle and hooking up clear vinyl hose to the end....use the squeeze handle to service the brake calipers from the bottom. The device with opaque/see-thru garden sprayer tanks makes it easy to see sufficient fluid remains to avoid introducing air.

Here's one Home Depot sells for less than $10:

Garden Sprayer Home Depot.jpg

Anyway, I was impressed with the simplicity and effectivity of the cheap vacuum-squeeze tool, at least for the purpose I mentioned of testing a vacuum system gauge.

[blueldr]

When I was in the USAF, that garden type pump tank is like the one we used to bleed the brakes on the B-36 and the C-124. In my entire aircraft maintenance life among general aviation type airplanes, I don't believe I've bought enough red hydraulic fluid to fill onr of those garden tanks.

[bagarre]

Most brake fluids will absorb moisture over time and shouldn't be kept on the shelf.
DOT5 is the only one that I know of that wont because it's silicon based.

I've always been told to use a fresh can of un-opened fluid when working on brakes and throw away the leftover.

And never mix DOT3 and DOT5 or any fluids for that matter.

[bagarre]

I unknowingly mixed DOT3 and 5 in the front brake of my motorcycle once. Within an hour or so, it swelled up, locked the caliper and left me stranded on the highway. I had to cut the line to release the pressure and get home.
The fluid turned into a nasty jello.
I don't recommend it.

[170C]

If any brake fluid (aircraft) left over after opening a container should be tossed I sure have a lot to be wasted. I have a gallon can that has likely had only a pint or so removed. The two holes have been sealed with good ole duck tape for years. Haven't had to use any as my small oil can is almost full of the fluid.

[GAHorn]

There are large differences between aircraft hydraulic fluid and automotive brake fluid.
(auto brake fluid is hygroscopic..absorbs water...and is why theres a rubber membrane on top of the fluid in your auto master cyl...5606 hydraulic is petroleum based, not synthetic)
There is no reason aircraft hydraulic fluid cannot be stored long term in a container intended
for chemicals such as a sprayer. The fluid sits for years in a vented master cylinder!

[GAHorn]

So all my effort to keep my big can sealed up all these years was in vain!

I wouldn't say that.... it's good practice, ......all petroleum products will experience some degree
of evaporation and oxidation, but as long as air exchange is kept at a minimum ....5606 has a long shelf life.

[FredMa]

The practice of not using already opened hydraulic fluid or engine oil is widespread in aviation but does not apply to the individual operator/owner. In the airline or FBO environment picking up a container that has 5606 written on it and using it when you have no earthly idea how old it is, what other chemicals have been mixed with it etc. is just asking for trouble. That is what I believe the practice is intended to prevent. I once knew a color blind mechanic that picked up a container marked 5606 and proceeded to service the hydraulic resivoir. Turns out someone had put Alodine in the bottle. It contaminated the system requiring every single hydraulic line and component on the aircraft to be changed due to corrosion.

[bagarre]

I didn't know that aviation brake fluid was anything other than DOT3. That's good to know and does explain the vented master cylinders.

The practice of not using already opened hydraulic fluid or engine oil is widespread in aviation but does not apply to the individual operator/owner. In the airline or FBO environment picking up a container that has 5606 written on it and using it when you have no earthly idea how old it is, what other chemicals have been mixed with it etc. is just asking for trouble. That is what I believe the practice is intended to prevent. I once knew a color blind mechanic that picked up a container marked 5606 and proceeded to service the hydraulic resivoir. Turns out someone had put Alodine in the bottle. It contaminated the system requiring every single hydraulic line and component on the aircraft to be changed due to corrosion.

Being a color blind pilot, I don't trust anything without a sealed cap

[blueldr]

I find it terribly hard to believe that someone would work on a general aviation aircraft brake system and not know that it used other than an automotive brake fluid. What in hell are they doing dipping into something they obviously know nothing about? What other things have they been working on without basic knowledge? How in hell did they acquire an A&P license, or are they just screwing around blindly like they do on their VW Bug?

[GAHorn]

The practice of not using already opened hydraulic fluid or engine oil is widespread in aviation but does not apply to the individual operator/owner. In the airline or FBO environment picking up a container that has 5606 written on it and using it when you have no earthly idea how old it is, what other chemicals have been mixed with it etc. is just asking for trouble. That is what I believe the practice is intended to prevent. I once knew a color blind mechanic that picked up a container marked 5606 and proceeded to service the hydraulic resivoir. Turns out someone had put Alodine in the bottle. It contaminated the system requiring every single hydraulic line and component on the aircraft to be changed due to corrosion.

The abhorrent behavior (to my mind) was the person who put alodine in a 5606 container without clearly marking the container otherwise!

A gallon can of "Hydraulic Fluid - Mil 5606" which has been opened and the contents not exhausted... should be closed up and placed back on the shelf for future use. The only reason to toss it into the trash would be if an FBO wanted to charge each customer for a full can of fluid! I'm tired of seeing "misc" charges on repair invoices, supposedly for the purpose of covering "shop materials" such as hand-soap and LPS-1 and paper towels. As far as I'm concerned. those are shop supplies and are the cost of doing business...same as electricity, water, and toilet paper in the bathrooms. I NEVER pay those charges and demand they be deducted from all my invoices lest shops be encouraged to continue the practice. (Would you accept it if a restaraunt charged you for napkins, salt/pepper, or catsup?)

A shop once charged my employer for 100 ft of 18 ga. wire simply for installing a new Hour Meter (which required about 8 ft of the wire.) When they told me they had to obtain a new roll of the wire in order to service the request with the appropriate 18 ga. wire.... I made them hand me the roll of the remaining 92 feet! (They couldn't find it of course, so I made them provide me with another.... I ended up with a full roll, of course! They got the point!)

I have a few gallons of Hyd 5606 for similar reasons. I don't let them get away with that cra.... stuff!

[N2255D]

I find it terribly hard to believe that someone would work on a general aviation aircraft brake system and not know that it used other than an automotive brake fluid. What in hell are they doing dipping into something they obviously know nothing about? What other things have they been working on without basic knowledge? How in hell did they acquire an A&P license, or are they just screwing around blindly like they do on their VW Bug?

Helped with an annual on a 170 in the mid 1990's. It was the first time we had worked on this airplane and found the owner had been using ATF in place of 5606. It's red so it must be alright . Took 3 weeks to finish that annual.

[bagarre]

I find it terribly hard to believe that someone would work on a general aviation aircraft brake system and not know that it used other than an automotive brake fluid. What in hell are they doing dipping into something they obviously know nothing about? What other things have they been working on without basic knowledge? How in hell did they acquire an A&P license, or are they just screwing around blindly like they do on their VW Bug?

To my defense, I've never worked on an aircraft's brake system and I'm not an A&P.
If I was to ever service the brakes on my plane, I would certainly find out what the proper fluid is before grabbing anything off the shelf, the same way I research everything I do before I do it.

My comment was about "most brake fluids" absorbing water and if it could be left on the shelf. I was not recommending someone use DOT anything in their brake system.