How to Perform a Cylinder Leak Down Test
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- เผยแพร่เมื่อ 20 ธ.ค. 2021
- I found what looks like a rebuilt 4.7 HO V8 engine at Pic-a-Part from a 04 Jeep Grand Cherokee Limited. After removing the camshafts I noticed that the cam gears and timing chains were like new and after looking at the engine block I realized that the engine looks to be rebuilt recently. To find out the condition of this engine I'll show you how to perform a cylinder leak down test. I also do a comparison of the Harbor Freight US General 94190 to the OTC Cylinder Leakage Tester Kit.
OTC's Cylinder Leakage Tester Kit quickly diagnoses internal engine problems like bad rings, valves, and leaking head gaskets and comes complete with adapters for most applications
Dual 2-1/2 inch gauges read 0-100 psi.
Kit features a pressure-regulated manifold with quick couplers, 24 inches long 14mm flex hose, and 10 mm, 12 mm, and 18 mm thread adapters. amzn.to/3EjCkxI
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When you do a cylinder leak down test. Just turn it up until the first gauge is at 100 PSI then just subtract the second gauge from the first gauge for your percentage of leakage. No chart needed.
Thank you for taking the time to make videos for us to learn and enjoy.
Glad you like them!
One extra step that should be performed on the OTC style leakdown tester is to compare gauges before connecting the hose to the cylinder to make sure they match pressures. If they don't then note the difference and add/subtract this difference when doing the actual test.
Thake you Mr.Martin...you are always the best.... respect respect 🙋👍👍👍 from Jordan
Thank you. I appreciate the kind words.😊
Like you I had a different gauge from China, and I think you actually lose some air once you connect it, so I did the same as you and bought the OCT gauges, really pleased with them!!
Thank you sir! Just subscribed to your channel as I am a mechanic 👨🏽🔧
You are truly a master!!! Watching you is pure educational joy! I like your work, your thoroughness, your tools and garage. Wish I knew you, feel like I do. I just love working on and watching people work on cars. Can't do as much as I used to, but it still pulls at my heartstrings!! Weird, huh? You sure do great work, and your explanations of each step is fantastic. Sure is a big help since not everyone shares their knowledge so freely. No doubt about it, next to my Daddy you are number 1!!! Daddy used to say "Yep, taught that boy everything he knows; just not everything I know", then he'd laugh. He liked teaching anyone who wanted to learn. Well, that's enough from me. You have a great day!! You sure lucked out on finding that engine! It looks good. Bye...
Wow, thank you for watching and for the support. I really appreciate that 🙏🙂
Have a wonderful Christmas 🎄 😊
I haven't even watched this yet but thanks for posting it. I have this planned for probably my Christmas weekend .
That sounds great. Have a wonderful Christmas
Awesome video Martin, you saved me money from buying the HF tester, merry Christmas my friend 😁👍
Thank you, Dave, and a Merry Christmas to you and yours. 😊
Bless you very much there Martin 🤴🧸🔔 🦌🎅🤶 Merry Christmas!
Thank you and a Merry Christmas to you and yours😊
Very good explanation between the cheap versions you can find from China and the otc. I bought from your link.
Martin, frohe Weihnachten! Alles Gute! Merry Christmas!
Thank you, and a Merry Christmas to you and yours. 🤗
Awesome video
Thank you, I really appreciate that.
Really good analysis Martin 👍 I wish used 4.7ltr motors were that cheap in Australia 🇦🇺
Thank you, Jason. Yeah, Pic-a-Part has reasonable prices on almost everything.
Good video on this tester. Those other testers don't allow you to apply enough pressure to give you an idea of what's really going on inside the enigne nor are they accurate.
You have some great videos. I learned a lot. I would like to know your opinion on the Pontiac 389 motor for a street build. Not for the track, but at least competitive on the street. Thank You
Very instructive video.I really like the detailed presentation. I need to do the same test on my '86 Bronco that came with a 5.8L , 351W engine. The truck has not been started for 12 years and whoever had it, removed a bunch of hoses and messed up the starting circuit. I've inspected each cylinder with a borescope and pistons looked clean with minimal carbon deposits but being 040 pistons tells me that the engine was rebuilt.I just want to know the status of the engine and the info you've presented in your video helps me a lot in that respect !Thanks for posting ! Subscribed.
A .040 over 351W that's awesome. I'm glad you found this video informative and helpful.
Thank you for watching and subscribing.👍😎
There's a easier way to get to TDC install the hose for the tester put a small balloon on the end turn the engine the balloon will start to expand as it gets to TDC.this will be very helpful when the engine is in the car or truck.
Just did my first LDT and was worried about finding TDC. Used a shop glove and this trick worked absolutely awesome! Thanks for the tip!
@spencerleeb glad I could help.
I can't take the credit,
though. I got the idea from a TH-cam channel,the channel
name is oldskool tried and tested.
Some good diy stuff on there for fixing cars.
Nice job Martin.I wish I had a couple of those H.O.engines just laying around.😂😂😂 Merry Christmas buddy.,
Thank you, Dan, and a Merry Christmas to you and yours. 😊
I wonder if, in an engine with miles on it and installed in the car, you could get a good result when cold and then when the engine is at operating temperature you could get a leak in one or more cylinders that were not previously revealed, like in the head gasket for example. Thanks for demonstrating the huge disparity in results for the two testers. It seems like HF no longer sells that type and sells one they branded "Maddox" that is like the OTC type.
I use one of those metal straws that you can buy, to determine tdc. They’re quite lightweight and won’t really damage the piston. It may squash the straw a bit but I would just use another.
Excelente video
Thank you Raul, I appreciate that. I'm glad you liked it and found it helpful.
I just bought this exact leak down tester and used it today on a pair of Yamaha F300 V6 4.2L outboards. Best I can tell you can, at best, make only relative, and not absolute, measurements. Specifically the manufacturer does not specify and refuses to disclose the orifice size. The % leak down table included with this tester does not specify bore size. Between these two missing pieces of information the only thing you can use this tester for is to quantify the differences between cylinders. So assuming you have at least one "good" cylinder then you have a known good reference that you can judge the other cylinders against. I would love for OTC to comment on these two points. Again, if you do not know the orifice size or calibrate the results for bore the % leak down number has no meaning whatsoever.
Buena noche vi un video d comparativa d lang tools y otc
Y el otc tiene muy poco % d perdida el lang tools se veia mas creible la perdida
En un motor con poco kilometraje a temperatura d trabajo la perdida con el lang tools era del 7 % mientras el otc solo daba una perdida del 3 %
Thanks!!
You're welcome. I'm glad you found it helpful.
To find top dead center for every cylinder just locate top of piston one. on crank pulley call it zero degrees any where on the pulley then just divide 360 degrees by the number of cylinders and mark your pulley every x degrees. Ex. 360/4= 90 so four cylinder engine is at every 90 degrees from your origen. Apply same idea to 6 and 8 cylinders and mark you have found top dead center for every piston. Enjoy
But it might not be on the compression stroke so you could also take the distributor cap off and make sure the rotor is pointing near the contact for #1 cylinder? Maybe it won't work on some cars without rotors.
Very good video - I like your easy to understand explanation of each step. One question though - your method of finding TDC seems like would be fairly likely to scratch the side of the cylinder. You did sort of address that, but surely there's a safer way to find TDC for each cylinder?
Pencil? 1/8 or 1/4 wooden dowel?
@@equanimousawareness Yep - I used a quarter-inch dowel. Worked well.
The procedure on aircraft is to use the type of gauge you used first.
The pressure is brought up to 80 psi during the test. The second dial should remain above 60psi.
It makes a difference if the engine is hot or cool.
Aircraft are checked while hot.
At 80psi the math is easy. 60psi = 25% leakage.
How much difference between cold and hot % leakage results is typical or acceptable?
@@captainwho1 I don't know the answer to that.
I own and maintain my own light sport aircraft.
On my Jabiru engine it would make about 6-10 psi but As I understand it on a Rotax engine it makes little difference due to the coating on the cylinders.
I believe the manuals for my aircraft call for it to be done with the engine hot, but please relalise i am not LAME I am an approved maintainer for MY aircraft and I am speaking from personal experience with my aircraft..
The FAA (Aircraft Piston engines) calibration spec is 80 psi. An 0.040" drilled test "Leak" should indicate 50% Leakage.
I have a subaru legacy that overheated and started getting a misfire. The misfire was only when the car was warm. I did this test when the car was cold and it tested good. But than I did this with the car warm and that's where I saw the air coming out of the radiator cap. So Sometimes when you do this test on a motor that is not installed or has been sitting for a while can be misleading.
Thank you for your input. I appreciate it.
Oil dipstick is what I use to look for tdc.
I really like that idea 👍😊, thank you!
*I’m doing a cylinder leak down test on a 302 Ford Small block, and I have a couple questions. When I finish the test on one cylinder, do I leave the Spark Plug out and continue to the next cylinder, or do I put the first Spark Plug back in and take the next Spark Plug out for the next cylinder? Another question I have is, do I need to drain the oil and leave the oil drain plug out? I was recommended by a buddy to do this. Last question, my buddy said something like “make sure the exhaust valves are completely sealed”… how do I make sure of that? Thanks everyone!*
Very well done. It seems we get the leak down result right away, we don't have to watch the gauge for a prolong period, say 1 min, to see if there is a drop in psi; right? And if everything is fine, the crankcase is the only place to which we lose air; correct? which we would hear through the oil filler?
Thank you i'm glad you're liked it and found it helpful.
Yeah, technically, it would be nice if there wasn't even any air going in the crank case. But that would be in a perfect world now. If you're getting a large amount of air into the crank case, that would be a sign of worn rings or cylinder wall, possibly broken rings stuff like that..
@martinbuilt what about. if when you apply air. it pushes the cylinder down? that will open a valve and give a false reading?
Wow what a great sign congratulations. What is the temperature of the motor affect the rate of loss? So if your motor was warmed up you would probably have even better percentages
Maybe not with a head gasket problem where it gets triggered by thermal expansion and seals back up when cold.
@@captainwho1 good point
Great vid. I’ve followed your instructions but for some reason when I turn the pressure knob up to 75 it stops about 69ish and goes no further. I did cycle the crank back around until I got tdc again but same thing won’t go over 69. Is my tester broke(otc)?
are you sure the incoming air pressure was over the 69psi
How to test oil rings ?
Still don’t understand tdc and how to find it or how to know when u have it
Both gauges on the Tester should be Identical psi calibrated units....The questionable Harbor Freight tester uses 2 totally Dissimilar psi gauges & could Probably be fixed by replacing Right side gauge with a quality 100 psi unit..
Very helpful video. How come you didn't have to lock the crankshaft somehow when you sent air in? When I did this it kept turning the motor over
Either you really had the pressure turned up to like 90 or a 100 PSI or or you had all the spark plugs removed and there was no compression on any of the cylinders and made it easy for the engine to roll over.
Thank you and I'm glad you found it helpful.
If the piston is at exact TDC it will stay there no matter how much pressure you put in the cylinder.
@@wcjcncI agree!
Boa tarde,a respeito dessa ferramenta otc-bosch 5609,ela é precisa,tem uma boa qualidade, eu tenho oficina mecânica e tenho interesse em adquirir uma dessa para teste,você me indica ela.Silvio do Brasil 🇧🇷.
good job. but why 75psi not 90psi????
jump to 14:00
The knob
Can you tell if the bottom end of a engine is good by doing a leak down test,if so how??Thanks
Yes, it would detect things as excessive blow by broken rings or holes in the piston.
You would hear the air rushing into the bottom end of the engine through the oil cap.
Are you always going to hear the air going into the crankcase? I've done 4 cylinders so far and I can slightly feel it escaping from the hole where the dipstick goes. Air is nothing major. And if I'm doing the leadown right. It's about 8% each one.
Yeah most likely get the most leakage from the crank case.
@@martinbuilt so this would be normal?
And the other question is what about at operating temperature?
Hello, why do you need TDC with rocker arms off? Could it be at bottom dead center?
Thank you!
Yes technically you could have the Piston pretty much at any location as long as both valves are closed.
Thank you for watching.
Push the know up and lock the unit
I’ve got a 2007 Jeep with the 4.7 that has cylinder number 8 with zero compression. I need to do a leak down test on it. What the best way to get cylinder #8 to top dead center?
Sounds like a dropped valve seat,😕 The borescope I just got from Teslong NTS500 would work great for this situation. It has 3 cameras and you are able to see the valves. Try just hooking up the air hose to the spark plug hole and see if you can hear where the air is going. Rotate the engine slowly. I think you will find the the air continues to blow out from one of the valves.
@@martinbuilt
I was thinking that if the engine has a TDC mark for number 1 on the timing cover then TDC for number 8 should be the next 180 degrees. I’m thinking it’s a valve seat also because the owner changed the radiator and didn’t bleed the air out of the cooling system and he over heated it.
@@weshawkins7165 Yes most likely the valve seat dropped. 😕
I need your help asap
Want seems to be the problem
I'm working on a small engine 2 cylinder...only showing 4% leakage in both but i hear/feel air coming from oil fill cap & dipstick tube is this normal?
yes, that would be the most common place where some leak would occur.
Thank you for watching.
@@martinbuilt so should i be replacing rings or do you think this is normal? Oil level is perfect , no smoke & machine runs great. But there is a slight smell of gas on the oil fill cap...but this is also a turbo engine that creates excessive blow by. Thoughts?
@@nowukno9 I think you are good to go.
@@martinbuilt my thoughts as well. Ill do a leak down every so often and keep an eye on it. Thanks for the video. Helped alot
If all the valves are closed why would it matter if the piston is at TDC or not? 100 psi is 100 psi at TDC as well as BDC. Right?
Good question...Cylinders tend to have more wear (& more leakage) near TDC...The crank has Less tendency to Turn from air Pressure when at TDC.
@@tomstrum6259 You mean BDC right?
🙂👍
Thank you for watching. 😊
Have u ever seen the way someone would use rope to lock up the engine so they can tighten back up the crank Bolt?
Yes, I sure have and have done it myself. I've done the rope trick to hold the valves up in place while changing out valve stem seals.
smh. Great video of what NOT to do. A hardened steel punch is the last thing you want to drop on your piston, then wedge into spark plug threads. For less than $20 you can get a TDC threaded indicator. If not, USE WOOD/PLASTIC DOWL. lol, maybe this guy sells Helicoil spark plug thread repair kits, very clever marketing.
360 because the cycle is 720
I just bought a cheap eBay leak down tester exactly like your Harbor Freight one. 🤦🏻♂️
Yeah so it would have been just like this one here.
www.amazon.com/dp/B0913FJNXK/ref=cm_sw_r_as_gl_apa_gl_i_E47BAM52D8Y8NXKXF55H?linkCode=ml2&tag=martinbuilt-20
@@martinbuilt yes exactly. But since watching your video I also watch one by “DIY Dave” who has a channel where he is trying various chemicals to reduce oil consumption on his Toyota Corolla. In one of those he does a leak down test using this cheap eBay / Amazon kit and it appears to work really well. Zeroing appears easy. I wonder if you just had a bad one?
th-cam.com/video/qCU8z7FgFPo/w-d-xo.html
What are the dudes doin? Theyre turning the crank while the gauge is on there.
Best done with a stripped down engine. HF tool was junk. Disposable tool. Cable tie is a better TDC or wood dowel.
OK, The reason you do not like the Harbor Freight instrument is because you do not understand the principle of "Pressure Drop" across a fixed orifice!!
The HF instrument Gives a Direct reading of the pressure drop. Thus it indicates the percentage of leakage based on the calculation of a specific orifice size in the instrument.
The OTC tester gives pressures before and after the orifice... THEN you Must use a separate chart to determine the percentage of leakage.
SO, It is simply a matter of personal preference as to which instrument one chooses to use.... OK
No I don't like it because it's a POS
The original HarborFreight cylinder leak down tester made by Pittsburgh is garbage. Harbor Freight now sells a good cylinder leak down tester made by Maddoxx. Also, you do not have to reference a chart to figure the percentage of leak down. You can turn the tester up until the first gauge hits 100 PSI then subtract the second gauge from the first to get the percentage of leak down.
They both must use that same principle but the OTC one allows you to test at a much higher flow rate through that orifice, by the ability to set the regulator to a much higher level. Seems like it would make it easier to hear, even with a stethoscope, small amounts of leakage, say through the intake valves for example.
Ohh hey also go to pick a part and find 07 & Up 3.7L 4.7L Oil fill tube, it’s a noice upgrade so you don’t have that milky crap around the oil fill … yeah it’s a smaller fill tube but least yah ain’t pouring new fresh oil down ontop of that milky crap…
Here's a video that I did on that upgrade.. It also makes the engine Bay look a little bit cleaner with less plumbing.
th-cam.com/video/omr0lfU8LFc/w-d-xo.html
I just did that test on a boat with the original tester, and would pump about 60 lb of pressure, and listen for the sound, it would come from both oil caps, what can you tell me about that?
Sounds like the air is escaping past the piston rings, which you're gonna have.
It is the amount of air that you're losing. If you're within specs, it's all good.
Harbor freight hand tools are great but as far as using these cylinder leak down tester NO WAY ! just cheap China junk !