Leak down test kit

[bobcharl]

Anyone out there have an unwanted leak down test kit to suit Rotax 912 for sale?

 

Please reply on thread.

 

Bob.

 

 

[billwoodmason]

Anyone out there have an unwanted leak down test kit to suit Rotax 912 for sale?Please reply on thread.

Bob.

About $35 on Ebay.

 

 

[bobcharl]

Thanks Bill,

 

I have looked at the Ebay adverts, but how do I know if the orifice is Rotax specification?

 

Bob

 

 

[old man emu]

https://www.rotax-owner.com/pdf/compression_912.pdf

 

The orifice size is 1 mm (0.04").

 

DANGER!!!!

 

When you let compressed air into the cylinder, it is going to push the piston down, which will rotate the crankshaft.

 

The prop is going to turn. So you need someone to be holding the prop against the turning of the crankshaft BEFORE you let the compressed air into the cylinder.

 

OME

 

 

[skippydiesel]

https://www.rotax-owner.com/pdf/compression_912.pdfThe orifice size is 1 mm (0.04").

 

Not so sure about this - the 1 mm/87 psi spec refers to a very upmarket, probably aviation specific, leak down tester that has a slightly different operating mechanism to the common or garden EBay $30+ type.

 

DANGER!!!!

 

When you let compressed air into the cylinder, it is going to push the piston down, which will rotate the crankshaft.

 

The prop is going to turn. So you need someone to be holding the prop against the turning of the crankshaft BEFORE you let the compressed air into the cylinder.

 

I have a slightly different experience - I took an EBay unit, modified it with some "Devcon" down to the Rotax 1 mm orifice specification and due to this restriction had apparent no piston movement.

 

OME

[bobcharl]

Hi OME, Your quote "Not so sure about this - the 1 mm/87 psi spec refers to a very upmarket, probably aviation specific, leak down tester that has a slightly different operating mechanism to the common or garden EBay $30+ type." is really the nub of my query.

 

It seems to me that the orifice size would need to be matched to the engine side gauge in the case of these types because the only ones I have seen have this gauge calibrated in % leakage rather than pressure. Do you think altering the orifice as you have would destroy the relativity between it and the % gauge, requiring a re-calibration of the gauge?

 

What are most Rotax owners out there using, as this being done every 200 hrs must make it a rather common procedure?

 

Regards,

 

Bob.

 

 

[old man emu]

I think you'll find that the bit you quoted is not mine. I think it is Skippydiesel's comment.

 

Here's a good explanation of what the orifice does.

 

Leak-down tester - Wikipedia

 

 

[skippydiesel]

[quote="bobcharl, post: 677220, member: 6373"

 

What are most Rotax owners out there using, as this being done every 200 hrs must make it a rather common procedure?

 

Regards,

 

Bob.

 

I would guess that most are using a compression tester and /or feel for the engine compression as they do their pre 1st flight of the day "gurgle" .

 

 

[Downunder]

I have this... DIFFERENTIAL CYLINDER PRESSURE TESTER MODEL E2A-12MM ROTAX from Aircraft Spruce

 

Pretty sure anything under a 5 inch bore uses the 1mm (0.040") orifice....

 

 

[Brett]

Add about $200 to that us$ price to get one in Australia through

 

 

[skippydiesel]

If you relay want to reduce the "orifice" on an ebay tester - just fill it with Devcon (or any epoxy) when it sets reduce depth/length of plug down to about 10 mm (or less) using a drill then with a 1 mm drill bit make your reducer - Simple!!

 

 

[MartyG]

Thinking on buying a leakdown tester and compression tester so can do own servicing, What capacity/ minimum PSI compressor is needed?. Also the Savannah manual says the compression(Differential pressure gauge) should be checked at the 25hrs service, Read somewhere it was every 200hrs? Previous owner had Annual done at 571hrs then leakdown done at 592hrs for condition report (1) 76/80 (2) 74/80 (3) 78/80 (4) 76/80 Aircraft currently at 621hrs. Cheers

[old man emu]

7 hours ago, MartyG said:

What capacity/ minimum PSI compressor is needed?

You only need a compressor that can pressurize the cylinder to 80 psi for your particular engine. Basically what a leak-down test says is "If I increase the pressure in a cylinder to a known amount, how much will it keep in. If you had unseated valves or worn rings/cylinder you would not get the sort of figures you quote.

 

How often to do the test? It is a simple, non-destructive test. You could do it every time you clean the spark plugs. The manufacturer's recommendation of every 25 hours lets you monitor trends. Don't forget to record the results in the engine logbook - adds to resale value.

 

SAFETY WARNING

Keep away from the propeller while doing this test. You are increasing the pressure in the cylinder well above atmospheric pressure. There is the possibility that the increase in pressure could cause a similar effect to the increase in pressure during a normal combustion cycle and therefore cause the propeller to move rapidly and give anyone in its arc a nasty thump.

[facthunter]

You hold the prop near TDC.by some secure means(STRAP).. IF a valve is leaking you'll hear Right on it there is NO torque but shift it a bit AND...  Personally, done right you can "FEEL" the compression very effectively and you do  this when "Burping" a Rotax or when priming and propswinging others (armstrong starters).  IF a valve is leaking you'll hear it in the appropriate area Air inlet or exhaust system  Rings it will come out the breather.  Nev

[Old Koreelah]

I like Nev’s idea that the daily hand turns give you a pretty good idea of the health of your engine, but that presumes far more experience and “feel” than most of us have. Having hydraulic tappets is another reason to be more precise.

My plane is currently at home in the container, waiting for me to find a few weeks to do lots of maintenance.

Great opportunity to make my own leak-down tester, based on an old spark plug with a pressure gauge attached.
Has anyone done this?

 

[facthunter]

You might as well put your thumb hard over a plug hole and turn the engine. Be careful IF you have "impulse magnetos". Remove all plugs and eart the leads. If you want a realistic compression test. Fly the plane for a while first but don't fly it IF it suspect to any degree. Use a boroscope to examine the bores if it's sat for a while and is NOT Nikasil  (which doesn't rust).  You may still have rusted/ sticky valve stems. Nev. 

[old man emu]

52 minutes ago, Old Koreelah said:

waiting for me to find a few weeks to do lots of maintenance.

You only have until 19 May 2023 to get it into the air to fly west for 90 Nm.

[Thruster88]

On 24/08/2018 at 9:43 PM, billwoodmason said:

About $35 on Ebay.

 

 

Those $35 ones on ebay are not worth considering. The gauge showing input pressure, usually 80psi and the gauge showing cylinder pressure must be the same type. We then get the reading 75 over 80 etc. I have yet to see a rotax 912 with less than 78/80.

 

[facthunter]

The only compression loss with some Rotax's would be IF they used leaded fuel producing  a build-up on the seats which partially detached. The Rotax doesn't run hot enough on the exhaust valve seat area for the Lead to work as it does on Air cooled engines.  Nev

[RFguy]

this one looks like a good option

May be available locally , also. 

https://www.aircraftspruce.com/categories/building_materials/bm/menus/to/test_cylinders.html

 

I have one of these

https://www.aircraftspruce.com/catalog/topages/diffpresse3m.php

 

I see they have one with the rotax plug thread 

https://www.aircraftspruce.com/catalog/topages/diffpress12mm.php

 

 

[MartyG]

Thanks for all the info guys, Found this on a Aussie site but doesn't say what size the orifice is but I will call them. 

https://premium-diagnostics.com.au/products/cylinder-leak-down-tester-compression-leak-detector-petrol-engines

[Thruster88]

1 hour ago, MartyG said:

Thanks for all the info guys, Found this on a Aussie site but doesn't say what size the orifice is but I will call them. 

https://premium-diagnostics.com.au/products/cylinder-leak-down-tester-compression-leak-detector-petrol-engines

I would not buy that. The second pressure gauge should have the same markings as the input pressure gauge. We dont use % in aviation, it is always just a number eg 65 over 80. Manufacturers will specify a minimum number. 

 

The one RFguy linked above is the one to get. It has two identical gauges and the correct orifice.  

[skippydiesel]

Yeah! go for the expensive one, you may live to regret it.

 

I believe that;

 

Much like oil sampling , this is  RELATIVITY test - for most meaningful results, should be conducted over the engines service life,  so that results from, near new/ low engine hrs,  testing can be compared/ relate to the testing of the same older/ high hrs, engine. 

 

The type of devise is not as important as consistency of measurement . If you are a home mechanic, servicing one aircraft, purchasing an expensive tool is hard to justify, when a cheaper one will probably serve your purpose.

 

One off tests/results will give you low quality information.

[MartyG]

59 minutes ago, Thruster88 said:

I would not buy that. The second pressure gauge should have the same markings as the input pressure gauge. We dont use % in aviation, it is always just a number eg 65 over 80. Manufacturers will specify a minimum number. 

 

The one RFguy linked above is the one to get. It has two identical gauges and the correct orifice.  

Ahh good to know, Cheers Thruster

[RFguy]

and for logbooks and maintenance, convention (and you really do want to stick to convention for such a critical engine health vital sign) is to write down the figure of the two gauges in psi. The type with a % gauge requires assumptions and assumptions are no good.... Buy the one used by aircraft technicians, has correct orifice, and correct gauging.