Thanks for this video. You explained it much better than the others I've seen. I'm just getting back into the hanger after a 35 year absence as a A&P Assistant.
There's little Pete! Wont be long and you'll be fighting him for the plane!! You are a lucky man to be sure! It seem like your family enjoys all the adventures as much as you do sharing it with them...good stuff.
i always wanted to know how to do a compression test, and what it tells you. Any pilot can understand this video...to the point : what you need, how to hook it up, where to hook it up and the process... excellent!
Casting a long shadow already! Excellent. Your prop turn for TDC reminded my how I had to just turn my 67 VW over by pushing on the rear bumper to find TDC on her air cooled power plant;o Thanks for the lesson!
This is not what I would call a cyl. compression test but a cyl. leak down test. It is better than a comp. test since actual cyl. leakage can be determined and measured thru valves or piston rings.
@blancolirio good job on the informative video,more power to your channel,a&p mechanic here also,trying to study more and learning more on piston engines,came from turbine aircraft,when pandemic came i was luckily got a job for company with small piston aircraft.👊🏻🤙🏼
Nice video Juan however I'm under the impression that this was a blow by test and not a compression test. A compression test is done by using a compression gauge in which you crank the engine over with the gauge attached in similar fashion. No compressor needed. The gauge holds the value of each compression stroke as you crank and you look for the highest reading after a few cranks. The blow by test I think is more accurate because you will also hear where your cylinder is leaking from. Through the Exhaust, intake or through the engine oil breather🤷♀️
On the cylinder being leak checked, the piston rings should be seated in the bottom surfaces of their lands, (ring grooves in the piston). To achieve this the piston must be coming up on its upstroke. If the rings are not seated in the bottom of their lands, the compressed air can escape thru the ring gaps, then under the rings and give a little lower gage reading.
Made my own leakdown instrument for auto/ outboard / other, modified a Horrid Freight. Found out HF DOES NOT use anything like standardized pressures/ orifice
Juan small correction what you are doing is Differential test ,many people confuse it ,,I just talk to Continental Engine About the same issues ,,Compression test is when you installed you gauge and Spin the Engine you will note it how high the compression test any others. Is not Correct
hi. thanks for share, great Job, can you please tell me something that dont tell in the video? you say that we should set the presure in 80 PSI but you do not say how much presure we shoul spect from the cylinder, when or how we will know that there is a loss of presure. Sorry my english, thank you!
blancolirio thanks for answering but i mean how much shoul be the presure in the other gauge ( from the piston) because you show in the piston number 1 a presure of 78 aprox, in other 75 and i dont know how much can go down as a normal or aceptable presure
Continental revised their specs in 2003. The master orifice reading of the day is the minimum leakage allowed. Could be as low as 46. And as long as you do a boroscope and everything still looks good and engine makes power - good to go.
i knew an aircraft that burned a hole n a piston, was a flight school. beech craft or something. it was the engine what was shut down all the time for training in flight. started surging over Montana where the hard deck was above the minimum altitude for single engine flight. when they got it on the ground they found it was from a hole in a piston
Technicaly that's a leak down test, not a compression test. A compression test is to see the pressure generated by the piston in the compression stroke. This tests for pressure leaking around valves or rings and shows what percent it is leaking
Pretty silly, isn’t it? I come from both worlds, and first learned the cranking compression test, then the aviation “compression test”. When I told my friends in auto shop about it, they said “oh you mean a leak down”. I thought that was a much better term. Believe it or not, that’s the FAA standard test and it’s required at every annual inspection.
You should put the piston of the cylinder you are checking to BDC, "bottom dead center" that way the prop can't spin around on you. remove the rocker arms as well to ensure the valves are closed.thrn listen to the exhaust, and the intake to see if you can here any air rushing threw that would indicate a bad valve, also listen to the oil dip stick tube to see how much is getting past the piston. on a liguid cooled engine look for bubbles in the coolant also.
Naa, just put it on TDC and give her the air...too much work and too dangerous to pull the prop up from BDC....I don't know anyone who removes rocker arms just to check compression, kinda misses the point...
blancolirio It's ok, when I was a young teen, I did it like you did, ONE TIME, then I learned my lesson, put the piston at BDC. You don't have to pull anything when doing a compression test. you're just checking each cylinder to make sure they all hold the same pressure. A cylinder with low pressure makes less power and causes the motor to run ruff, like a miss fire. Again, you don't need to rotate the motor when checking compression.
blancolirio What you're doing is more of a leak down test then a compression test. if you were doing a compression test you would use 1 gauge and crank the engine over to see what the compression is. that's a compression test
blancolirio If I'm doing a compression test, I unplug my coil, and pull the fuse to my fuel pump, then I pull my plugs and I connect my compression gauge to the cylinder, then I crank the engine which then my compression Gauge reads the compression on the compression stroke. I do that to all my cylinders to see if there within range of each other. if I'm doing a "leak down" test, I use my dual gauges like what you're using, then I use supplied air from an air compressor, same thing that you did in this video, then I monitor the gauge to see how well that cylinder is holding the supplied air while I listen for leaks. the operation you are performing is a leak down test, those are leak down gauges. you are seeing how well the cylinders holds air. I remove my rocker arms to make sure the valves are fully closed and not sticking, it's real easy to do on an aircraft engine, way easier then a automobile engine, takes 3 minutes tops.
In the automotive world that is called a leak down test & is showing the % of loss, a compression test is done cranking with a single gauge to show actual compression. Can anybody tell me why the difference in terminology?
Nothing different about it at all, the exact procedure shown here is called a leak down test in the automotive world, only the terminology is different. The question was "why".
If you use a single gauge and cranking the engine-it's a completely different method of testing, though the results may be similar. With an aviation compression test you can easily identify where the leak(s) are. I'm not too familiar with automotive style leak down testing procedures. The terminology comes from the use of two gauges measuring the difference of PSI from the source into the cyl vs. psi held by the cylinder, thus 'differential compression test'. If you have a link for an automotive leakdown test using two gauges I'd like to see it. Thanks JB.
FWIW - automotive compression test is a screening test for issues (pump up pressure when cranking) while the leakdown test is more definitive for location of issues once they are noted. Automotive gauge setup can be the same as aircraft for leakdown, with input & cylinder pressure gauges for comparison. The alternative 'quickie' or simple version uses a pressure regulator for the input pressure to Zero the single cylinder pressure gauge side when disconnected (from cylinder). When connected with air pressure supplied it registers directly as a percentage leakdown, as compared to the regulated input pressure. Same type number you could get from a comparison of inlet & cylinder pressures, just avoids the figuring & doesn't give the same ppwk. trail.
A little more involved than checking an automobile compression. Not sure he was really giving the prop the respect it needed. But just an observation as I certainly am not an certified aircraft mechanic. Master ASE otherwise.
if you have to pump the prop, you are doing it wrong. engines do not run backwards, if you do not like what you see rotate the engine to about 20-30BTDC, hold the prop and slowly open the air, when you feel the prop start to fight you, start pushing it to TDC while opening the air valve. you should hit TDC and full air at about the same time. you will know when you are TDC when there is no pressure on the prop, have someone put a ear in the exhaust pipe and oil fill listening for air. 35+yr IA,
Thats an automotive expression. In aviation its commonly referred to as a compression test. We don't do 'pump up' style compression checks like on cars.
I agree with David Perry; there should be some consistency in nomenclature across disciplines to avoid confusion. There is a reason why auto techs call this a cylinder leak down test, because that is the most accurate description of what is being preformed. A compression test is completely different and much less revealing which is why it's not acceptable or practiced in aviation. Believe that is something that important to be understood from an engineering standpoint. This test actually has nothing to do with compression when you think about it. It actually just gives implications towards how effective an engine may be able to produce compression. It's a test of the cylinders leakage.
It's called a differential compression test in aviation and the test results indicate in psi/psi, not psi/%. A differential compression tester is used, otherwise the same thing.
Compression test are good but I also would use a bore scope to observe the interior of the cylinder. The borescopes are relatively inexpensive and should be a must on any annual inspection.
+blancolirio Might want to check your AC 43-13 1b page 8-14 paragraph 5a which clearly states to check it hot. Also why does it matter TDC is TDC doesn't matter if it's for magnetos or not
Thanks for this video. You explained it much better than the others I've seen. I'm just getting back into the hanger after a 35 year absence as a A&P Assistant.
There's little Pete! Wont be long and you'll be fighting him for the plane!! You are a lucky man to be sure! It seem like your family enjoys all the adventures as much as you do sharing it with them...good stuff.
Juan, thanks for giving so generously of your time and expertise. Very much appreciated.
Thanks John!
i always wanted to know how to do a compression test, and what it tells you. Any pilot can understand this video...to the point : what you need, how to hook it up, where to hook it up and the process... excellent!
Casting a long shadow already! Excellent. Your prop turn for TDC reminded my how I had to just turn my 67 VW over by pushing on the rear bumper to find TDC on her air cooled power plant;o Thanks for the lesson!
Thanks. easy video to follow. In school to become A&P. this helped me remember the steps. Appreciate the video. Vard.
Now that's what I want to do with my grandson... aerocamping! brilliant! :)
Do it!
Thanks. I just had this done on the same engine in a 1948 8A. I was not able to be there for the test, and had been looking to see how it is done.
Nice job Ron. Thx. Keep the videos coming.
This is not what I would call a cyl. compression test but a cyl. leak down test. It is better than a comp. test since actual cyl. leakage can be determined and measured thru valves or piston rings.
@blancolirio good job on the informative video,more power to your channel,a&p mechanic here also,trying to study more and learning more on piston engines,came from turbine aircraft,when pandemic came i was luckily got a job for company with small piston aircraft.👊🏻🤙🏼
Nice video Juan however I'm under the impression that this was a blow by test and not a compression test. A compression test is done by using a compression gauge in which you crank the engine over with the gauge attached in similar fashion. No compressor needed. The gauge holds the value of each compression stroke as you crank and you look for the highest reading after a few cranks. The blow by test I think is more accurate because you will also hear where your cylinder is leaking from. Through the Exhaust, intake or through the engine oil breather🤷♀️
Brings back merrorys of a previous life when i was a ae apprentice
Excellent video and parenting!
Nice video. I do the same on the aircraft diesel engine, placing the probe on the injector housing instead.
Also referred to as a leak down test.
Nice simple video on the process, thanks for posting!
Great video Ron....Keep it up man.
On the cylinder being leak checked, the piston rings should be seated in the bottom surfaces of their lands, (ring grooves in the piston).
To achieve this the piston must be coming up on its upstroke.
If the rings are not seated in the bottom of their lands, the compressed air can escape thru the ring gaps, then under the rings and give a little lower gage reading.
great video!!! very well explained, thanks!
nice job men congratulations
You should use a straightedge to determine too dead center and compare it to Tdc mark.
GREAT VIDEO !
Thanks for posting
Great great great, thanks for the video, Isabel really helpfull
Totally awesome video
Made my own leakdown instrument for auto/ outboard / other, modified a Horrid Freight. Found out HF DOES NOT use anything like standardized pressures/ orifice
Juan small correction what you are doing is Differential test ,many people confuse it ,,I just talk to Continental Engine About the same issues ,,Compression test is when you installed you gauge and Spin the Engine you will note it how high the compression test any others. Is not Correct
Thank you for that info
Leak down test or compression test?
Thanks
well explained will help many i am sure ,,just about to do mine ,,,a65 conti
Thanks!
Thanks nice video
So what's the young engineer's report on the test .? 😊
so that engine is completely air cooled? looks like a sweet job.
+Landon Hillyard Yep! nice and light...
hi. thanks for share, great Job, can you please tell me something that dont tell in the video? you say that we should set the presure in 80 PSI but you do not say how much presure we shoul spect from the cylinder, when or how we will know that there is a loss of presure. Sorry my english, thank you!
from the indication on the other gauge...then listen for the leaks. Exhaust, Intake, or rings (crankcase breather).
blancolirio thanks for answering but i mean how much shoul be the presure in the other gauge ( from the piston) because you show in the piston number 1 a presure of 78 aprox, in other 75 and i dont know how much can go down as a normal or aceptable presure
depends on manufacturer, see their tech specs. Anything below 60 is pretty bad compression and should probably addressed.
blancolirio perfect answer. My engine is an 90hp Continental engine on a nice ercoupe. Thanks again. cheers
Continental revised their specs in 2003. The master orifice reading of the day is the minimum leakage allowed. Could be as low as 46. And as long as you do a boroscope and everything still looks good and engine makes power - good to go.
Good stuff 👍🏽
Greating from Brazil...
Nice 8a
Question for you, dont you have to use a master orifice tool on Continental engines? (A&P Pending...)
Only to check calibration.
A.p can do the anual inspection
greating from Quebec
Awesome very helpful
how much engine hour do I need to perform engine compression test...??
Set by the each engine manufacturer and mandated by the FAA.
great
i knew an aircraft that burned a hole n a piston, was a flight school. beech craft or something. it was the engine what was shut down all the time for training in flight. started surging over Montana where the hard deck was above the minimum altitude for single engine flight. when they got it on the ground they found it was from a hole in a piston
Yikes! It’s rare, but it happens.
Technicaly that's a leak down test, not a compression test. A compression test is to see the pressure generated by the piston in the compression stroke. This tests for pressure leaking around valves or rings and shows what percent it is leaking
Why do aviation people call this a compression test? In automotive that is called a leak down test.
Pretty silly, isn’t it? I come from both worlds, and first learned the cranking compression test, then the aviation “compression test”.
When I told my friends in auto shop about it, they said “oh you mean a leak down”. I thought that was a much better term.
Believe it or not, that’s the FAA standard test and it’s required at every annual inspection.
You should put the piston of the cylinder you are checking to BDC, "bottom dead center" that way the prop can't spin around on you. remove the rocker arms as well to ensure the valves are closed.thrn listen to the exhaust, and the intake to see if you can here any air rushing threw that would indicate a bad valve, also listen to the oil dip stick tube to see how much is getting past the piston. on a liguid cooled engine look for bubbles in the coolant also.
Naa, just put it on TDC and give her the air...too much work and too dangerous to pull the prop up from BDC....I don't know anyone who removes rocker arms just to check compression, kinda misses the point...
blancolirio It's ok, when I was a young teen, I did it like you did, ONE TIME, then I learned my lesson, put the piston at BDC. You don't have to pull anything when doing a compression test. you're just checking each cylinder to make sure they all hold the same pressure. A cylinder with low pressure makes less power and causes the motor to run ruff, like a miss fire. Again, you don't need to rotate the motor when checking compression.
+LS6 Z28 are you sure your an A&P.?!...lol
blancolirio What you're doing is more of a leak down test then a compression test. if you were doing a compression test you would use 1 gauge and crank the engine over to see what the compression is. that's a compression test
blancolirio If I'm doing a compression test, I unplug my coil, and pull the fuse to my fuel pump, then I pull my plugs and I connect my compression gauge to the cylinder, then I crank the engine which then my compression Gauge reads the compression on the compression stroke. I do that to all my cylinders to see if there within range of each other. if I'm doing a "leak down" test, I use my dual gauges like what you're using, then I use supplied air from an air compressor, same thing that you did in this video, then I monitor the gauge to see how well that cylinder is holding the supplied air while I listen for leaks. the operation you are performing is a leak down test, those are leak down gauges. you are seeing how well the cylinders holds air. I remove my rocker arms to make sure the valves are fully closed and not sticking, it's real easy to do on an aircraft engine, way easier then a automobile engine, takes 3 minutes tops.
In the automotive world that is called a leak down test & is showing the % of loss, a compression test is done cranking with a single gauge to show actual compression. Can anybody tell me why the difference in terminology?
Different kind of test. This is a "differential" compression check. No cranking.
Nothing different about it at all, the exact procedure shown here is called a leak down test in the automotive world, only the terminology is different. The question was "why".
If you use a single gauge and cranking the engine-it's a completely different method of testing, though the results may be similar. With an aviation compression test you can easily identify where the leak(s) are. I'm not too familiar with automotive style leak down testing procedures.
The terminology comes from the use of two gauges measuring the difference of PSI from the source into the cyl vs. psi held by the cylinder, thus 'differential compression test'.
If you have a link for an automotive leakdown test using two gauges I'd like to see it. Thanks JB.
FWIW - automotive compression test is a screening test for issues (pump up pressure when cranking) while the leakdown test is more definitive for location of issues once they are noted.
Automotive gauge setup can be the same as aircraft for leakdown, with input & cylinder pressure gauges for comparison. The alternative 'quickie' or simple version uses a pressure regulator for the input pressure to Zero the single cylinder pressure gauge side when disconnected (from cylinder). When connected with air pressure supplied it registers directly as a percentage leakdown, as compared to the regulated input pressure.
Same type number you could get from a comparison of inlet & cylinder pressures, just avoids the figuring & doesn't give the same ppwk. trail.
A little more involved than checking an automobile compression. Not sure he was really giving the prop the respect it needed. But just an observation as I certainly am not an certified aircraft mechanic. Master ASE otherwise.
if you have to pump the prop, you are doing it wrong. engines do not run backwards, if you do not like what you see rotate the engine to about 20-30BTDC, hold the prop and slowly open the air, when you feel the prop start to fight you, start pushing it to TDC while opening the air valve. you should hit TDC and full air at about the same time. you will know when you are TDC when there is no pressure on the prop, have someone put a ear in the exhaust pipe and oil fill listening for air. 35+yr IA,
seat the rings. 40 year A&P
You can't say "dike" anymore....the correct term is "Alternative Lifestyle.." as in "Would you please hand me the alternative lifestyle cutters..?"
So true.
HA! I recognize that gas station.....
That not a compression test. That’s a leak down test
If you are not an aircraft mechanic.
@@blancolirio the tester even says leak down tester
Thats an automotive expression. In aviation its commonly referred to as a compression test. We don't do 'pump up' style compression checks like on cars.
Completely different from automotive, interesting 🤔
...and watch your engine deteriorate over time....
leakage test is what is being done, not compression.
No, it's called a compression test in aviation, a leak down test is automotive jargon.
I agree with David Perry; there should be some consistency in nomenclature across disciplines to avoid confusion. There is a reason why auto techs call this a cylinder leak down test, because that is the most accurate description of what is being preformed. A compression test is completely different and much less revealing which is why it's not acceptable or practiced in aviation. Believe that is something that important to be understood from an engineering standpoint. This test actually has nothing to do with compression when you think about it. It actually just gives implications towards how effective an engine may be able to produce compression. It's a test of the cylinders leakage.
@@blancolirio
It may be an automotive term but at least it's accurate and makes sense.
It's called a differential compression test in aviation and the test results indicate in psi/psi, not psi/%. A differential compression tester is used, otherwise the same thing.
Compression test are good but I also would use a bore scope to observe the interior of the cylinder. The borescopes are relatively inexpensive and should be a must on any annual inspection.
Soooo... Couple of things. It's a glare shield, not a dash. Also, continentals timing marks should be lined with the bottom case split not the top.
P.s. Should always compression test the engine hot.
+Makarth no. Not true.
We're doing a compression test here, not magneto timing.
+blancolirio Might want to check your AC 43-13 1b page 8-14 paragraph 5a which clearly states to check it hot. Also why does it matter TDC is TDC doesn't matter if it's for magnetos or not
+Makarth Looking forward to your video presentation on this subject! Cheers!
!!!!!!!!!!!!........THAT IS NOT A COMPRESSION TEST MR MECANIC...THAT IS A LEAK DOWN TEST TO DETERMINED "WERE" THE COMPRESSION IS LEAKED FROM......!!!!
Thanks