Glad you liked my tip! That works on all motors, and the more centered you are on piston dwell at TDC, the safer you are against the crank suddenly rotating on you. I try to estimate the middle of dwell, and that IPA TDC finder helps me to a bit. Bore wear is usually greater near TDC, so measuring at the top can be important. Head gaskets are above the piston, so there is no concern about blocking the air pressure from escaping out the head gasket at TDC. The ideal air pressure is 100 psi, because it makes the math easy. The left gage reads how much air pressure goes into the bore. The right gage measures the pressure remaining in the cylinder. So that right gage is only dead accurate if the left gage reads 100%. Otherwise it's reading a percentage of a percentage! The OTC leak down tester has two gages that both read psi, and it includes a chart that converts the leak down % when using lower air pressures. That snap on gage is nuts if it thinks a 40% leakage rate is anywhere near acceptable. 15% would definitely indicate a problem!! At 40%, you have major blowby or valve sealing issues. You might also want to start the test at 0 psi on the regulator, and slowly increase the air pressure to 100. Much safer and less likely to rotate the engine suddenly. Otherwise, you had better be at true TDC in the middle of piston dwell. Engine should be warm as well, so rings seal correctly and cylinder bore is oiled up. FYI, piston dwells for probably 6 to 8 degrees at TDC... but the rod is still swinging side to side except when it's right near the middle of piston dwell. Visualize the piston, rod and crank as the rod rotates from one side of the bore to the other.
That's ok. Stay on this case, Paul. We need to find a test that can prove which valve leaks using a scope! Pressure is what leaks, so pressure must be how to find it. Probably at cranking speeds. Although at this point, it seems like the leak down test is still king. We could try splitting a shop air hose into two, both regulated to 100 psi, one going to the cylinder and the other going to the gauge. It would effectively be a scoped leak down test. Somehow, an in cylinder pressure transducer at cranking speeds would have to show something. I'm hopeful about the map or exhaust pressure sensor too.
To ScannerDanner!!!!!!!! It doesn't matter if it is a V (or W) engine, a boxer engine or an inline engine .. any piston and con-rod combination will have a point at TDC and BDC where the forces is directly inline with the throw of the crankshaft. Those two points during a crankshaft rotation is where the piston will come to a complete stop before changing the direction of travel, it is therefore also called a reciprocating engine. To be more specific the engine you are working on is a:"4-stroke Otto cycle reciprocating heat engine". Thus at TDC or BDC... ANY force exerted on the piston will NOT result in any torque transfer, and thus NO rotation of the crank. Again this also means that the maximum transfer of mechanical energy from the combustion of petrochemical energy (NOT an explosion as some wants to call it) is during the combustion stroke where the con-rod is perpendicular/orthogonal to the throw of the crankshaft. Remember "force times arm equals torque"... at this point the "arm", which is the throw of the crankshaft, is at its optimum position, and the force transferred perpendicular/orthogonal from the con-rod is using all the energy to turn the crankshaft.. therefore this is where the max torque is transferred.
SUBSTANTIAL Sir ScannerDanner Thank you for sharing what you know with us great tutorial brilliant video I enjoy watching video From the start to finish. God bless you and all your family around you Sir ScannerDanner From Nick Ayivor from London England UK 🇬🇧
BTW. As others have mentioned you should NEVER try to hold the wrench. Simple math (pi x r^2) for a 3" bore and 100psi will tell you that there is about 700lbs of force on the top of the piston and that's further multiplied by the stroke of the crank SO you're looking at a broken hand (as you almost found out). Putting the a standard xmission car in gear doesn't always work either. I've had the car move. If you must test at 100psi then maybe a long wrench jammed against something would make sense.
Good stuff as always man. I was actually surprised at how much controversy there was about a leak down test during this series lol. Back when I was a second year apprentice at trade school (here in BC, Canada, second year is focused on engines, rebuilding, diag, maintenance etc etc) we were taught to always do a leak down test at TDC for more accurate results and safety, but to do it at BDC after just as a secondary test to reveal any issues with a head gasket that might have been missed due to the piston covering the sealing surface at TDC. I always thought this was a pretty "textbook" test lol :) For better or worse, we learn new stuff everyday thanks to the internet :)
Great videos, in my experience doing leak out tests I have found that normal engines that have average wear are always about 10 to 20%..... 25% is a borderline time to overhaul, and 30% is need to repair now and usually a misfire or poor driveability issue has brought the car in for diagnosis.
11:15 I dont think a V type engine would be any different. As long as the connecting rod is perpendicular within the cylinder to the crankshaft it should stay.
Testing with piston down btdc should test for cylinder wear as well as a cracked cylinder wall. Also I use a vaccum/ fuel gauge to check when I don't hear a leak by ear. You can check for exhaust valve at tail pipe, intake valve at vaccum hose, crank case at dip stick tube, and head gasket at the radiator cap. This way you check all possible points for secondary leaks. I use smoke adapters to plug the snorkel and access tail pipe while using one of my assortment of rubber stoppers with one hole in them for the radiator. Btw these stoppers work great sitting on the p/s pump to pull vacuum to remove air from system.
I usually have the leak down tester set at around 25psi input and around the same on the reg so when I turn the crank to find TDC when the hold down gauge begins to rise it's coming to the top. The lower pressure makes it easier to turn the crank,TDC is easy to judge,if it's not then it spins the crank. Then dial up 100 psi on the input, Saves all the screwdriver down the plug hole process.
a timing chain, guides and tensioner can give you that problem with poor sealing valves, timing correlation, misfire, lean condition are also symptom related to a loose timing chain. great videos, keep it up.
Great video! Loved the cylinder comparison and different techniques. Just wondering about the t body. Always learned to never physically move the plate on a drive by wire setup.
I really was curious about that T body man. Is it okay? And if so why? Obviously I’m missing something. I’ve learned more from your videos than anyone else. Including automotive class instructors. I think you have said not to do that yourself So, let me know! Just need that knowledge!
A note on bdc vs TDC numbers. When I was in school in we would bore gauge cylinder wall wear... The top of the cylinder always read a larger bore than the bottom. I'm talking specifically about in line 6 engines here. It was only a few ten thousandths but it was noticeable. This also accounts for the common cylinder Ridge that can be felt in the liner at the top of the stroke, I've never seen a ridge in the bottom of the liner. I guess the thought is there is some cavetation taking place near TDC as the crank rolls over and shifts the direction of the connecting rod. This also happens at bdc but the piston is closer to the crank and under no pressure at this point. Just a thought as to why you're getting different % of leakage @ TDC vs bdc.
I have been watching all your videos including your premium channel and I have never heard you say anything stupid, until now :) Sorry, but I have to correct. Regardless of the engine type, TDC is TDC and the crankshaft centre line is straight up and down regardless of the engines design. V type or inline. V type just happens to be on an angle but the centreline is still straight up and down. Can I also say that doing a leak down test at various points of piston position in the cylinder especially if you are chasing a blow by problem is always a good idea. A scour in the cylinder does not always run the full length of the cylinder and a crack in the cylinder may be horizontal. I have seen this in race engines that have suffered serious detonation where it would appear the engine is trying to pull itself apart and a leak down did not show up with the piston at TDC. Wind the engine down a inch and bingo. Love ya work Scanner Man
Took my stepson's H3 to the dealer today for a check engine light, got a 0300 code and they said cylinder 3 misfire. Paid $200 for troubleshooting and they said the cylinder gets 160 psi (good), and the problem is leaking (down-leak?) into the crankcase, replace the rings. They suggested replacing the engine for over $9k, rather than rebuild the engine . We replaced the plugs with platinums (the installed plugs were roasted), cleaned the MAF and Intake, got a new air filter, got a full syn oil change and added 6 cylinder Restore Engine Restore. Have full system fuel injector cleaner to put in next fill up. Check engine light is still on, though only 3 hours later. Vehicle wasn't acting up , so no difference in performance since light came on. WHAT ARE YOUR THOUGHTS ON OUR SITUATION AND WHEN SHOULD THE CHECK ENGINE GO OUT, IF WE HAPPENED TO FIX IT? Thanks so much for your great videos and your time. Much appreciated.
I've seen leakdown testing done with different incoming pressures (usually lower). Is there an optimum intake pressure for the most accurate test? Presumably doing it with lower pressures might be a little safer....
Here's a clip of the one that I use... th-cam.com/video/aKwWCAlNRlg/w-d-xo.htmlm21s as pressure builds, you can see that the the "leak" side follows quite quickly from low to higher pressure. I think any where from 50 to 80 psi should be enough to find leaks. Obviously no leak in my video as I am just using the air to hold the valves closed.
I noticed in several shots that the input side pressure dropped off the initial 100psi set point to about 90 or less. Wouldn't it be wise to set that back to 100psi. That pressure affects the leak down gauge side measurement as well. It might make the difference between the gauge showing in the good or marginal range and change your opinion of the result. This is why I prefer the type with two regular gauges and look for the difference between them.Sage
Hi Paul, well I think what ever kind of engine it is the con rod and crank will all be in line at TDC, just one comment, when you do this with a Manual Transmission car you can put it in top gear with parking brake on to stop engine moving, I guess a lower reading at tdc prob means the bore is worn a bit at the top, I don't think valve overlap would come into it for quite a lot of crank travel, with the old distributor cars you can see what cylinder you are on by checking where the rotor arm is pointing roughly..cheers good video, I think you would only need to put oil down the bore if you were getting pressure out the oil cap - Fred in England
Good stuff- I do like the use of the MAP wave form and look forward to pico pressure transducer wave form, since the two are so much different it would be interesting if we could view the WPS500 wave form and be able to interpret the MAP wave form consistently.
I have the in cylinder readings on the pico coming up next. If I can I may use the WPS500 on the intake and maybe my fluke pv350 in the cylinder? Depends on what else is going on. It would be cool to see. I want to get a first look sensor in the tailpipe too but do not have one yet. It would be super cool to see all three.
Usually when an engine overhaul is done, the top part of the cylinder needs to be reamed to get rid of a ridge. If ridge is not removed the rings will expend and it will make the removal of the piston hard and it may even break the piston. Long story short, the top of cylinder walls wear more than the bottom part. That could be the reason for air escaping more on the top dead center from the rings. On the bottom, the cylinder is less worn and the rings seal better.
a coworkers case scenario ...basically followed these instructions on a 4 cyl. Toyota Rav 4 .... also had big leak out of the intake clinder 4...after teardown no problems found with valves...but tech was instructed to replace head and valves...warranty .... after put together ... still had a air fuel ratio imbalance on #4 ... removed valve cover... redid leakdown visually seeing the cam lobs were off the valves...leakdown did reveal leak out of crank case... NOT intake.... i would definitely recommend leakdown down with valve covers off instead of on... a broken piston was found on complete teardown.... just my opinion.
swillieboy so maybe the key then is to remove the pcv and breather lines to be sure it is not coming from the crankcase. this should fix that variable. great tip! thanks!
I'd like to see a secondary ignition wave form and look for hash on the spark line which would indicate valve sealing issues. Would this be possible? THANX
Always great content Scanner Danner appreciate the time and energy you put out. If you guys want to save money and learn how to build a leak down tester watch my "MAKING A CYLINDER LEAK DOWN TESTER AND CHECKING ENGINE INTEGRITY, PISTON RINGS, VALVE & SEAT SEALING" its simple.
Why didn't any of the valves open at BDC because of valve lead or lag, depending which way the engine rotated? I don't know cam spec for that engine but I assume the exhaust valve would have opened before BDC. Did you not allow the piston to go all the way down to BDC with the wrench? Great videos by the way.
Just curious as to how much shop air pressure you actually need to make the test accurate? Would be a lot easier to control the crank with 40 psi than 120 psi for example. Here is instruction on a harbor fright compression leak down tester: "NOTE: Set the air compressor’s regulator to 7 to 100 PSI. Never operate this tester with air pressure set higher than 100 PSI, which can damage this tool." Not sure if 7 psi is enough to even move the crank.
Hi Paul, sorry to resurrect such an old video (great series btw) but i am now personally starting to play about with a pressure transducer and a first look sensor so was wondering if you could share where you personally went for information regarding how to disect these waveforms? I know this is 5 years old now but at this point you were just starting to get to grips with this and i was wondering if there was a particular website or training book that you found useful on how to understand and interpret what you were looking at on the screen. Thanks as always Dave
GMC TSB# PIP4013C: In-line Truck Engine Misfire at Idle. Important: Before replacing the cylinder head, review the latest version of PIP3940, I forgot to mention this is a recall. you must change the entire cylinder head, what is bad are valve spring. the new head got this fix.
you always have some ring blow by cylinder wear is less at bottom of the cylinder than at tdc when you tear down a motor you always find more ridge at the top of the cylinder than at the bottom. leak down sees the extra wear at tdc and adds to the leakage. best to do test at bdc once then add oil to check for the amount of leakage added to leak down by ring wear.
Would it be true to say that running the compression test at TDC and then lower in the bore at different points be a good indication of bore taper wear ?
It is normal to have more wear near TDC as this is wear all of the major psi occurs in the cylinder. What I do not know is what is an acceptable amount. This is not my area of expertise.
Hey ScannerDanner, I have a car blowing blue smoke and has misfires, I did a cylinder leak down test and found 45% leak on cylinder 2 and found air coming out of cylinder 4 any idea what this indicates? Thanks
blue smoke is burning oil and that is a huge amount of leakage, I worry about a ring issue but that wouldn't cause air to come out of the #4 unless the rings are bad there too What are your compression pressures on all cylinders?
Putting a ratchet on the crank would be a lot safer because you can still apply pressure but if it wants to take off on you it wont fling the wrench and hurt you.
what happens when you have a blown head gasket to an adjacent cylinder and that cylinder has either the intake or exhaust valve open? would this not throw off the test? of course you would see this ounce you remote the head anyway.
Mike P For sure there are tons of variables with in-cylinder pressure waveforms. I would think you would catch this one easily on a relative compression test as pretty much two dead holes.
what if the cilinder comunicates to the neighbourg cilinder and loses presure through the intake valve of the neibourgh cilinder, valve that is normal to be opened in that moment.
@@ScannerDanner today I did added oil to all the cylinders in my mustang and it started up!!! I have a dead miss on cylinder #2 cylinder leak tested and it's coming out the oil filler and throttle body. Also smoke tested through the spark plug hole #2 and smoke came out the throttle body and oil filler hole. So my guess is it needs rings. Time to sell
You’re doing this test wrong. You do not pressurize the tester then plug it into the cylinder. You have everything connected all the way to the cylinder and then turn the tester up until the first gauge reaches 100 PSI, then you read the second gauge to get your percentage of leak down. Almost every video on TH-cam on how to do this test is wrong. It’s freaking ridiculous. Lol
wow. i want to but just cant due to work. i did buy your book a few weeks ago. very good work. u do autographs?!... cause one day your gona make it big with these vids
yea i was watching your fuel injector videos of them being stuck closed and open. would your old vantage graphing meter? be adequate enough to capture the pintle on the injector waveforms? im looking for something cheap and that looks older and probably cheap enough
just want to add a comment, my leak down tester instruct not to apply anything over 80 psi to the inlet leak down tester, that might keep from crank turning while doing the test, or might b my leak down tester is a cheap one lol.
Part 4? I understand it's a great learning experience for your students but compared to all of your past videos it seems like you're going overboard on your leak down results. Yeah it's the company vehicle and you want to ensure you're diagnosis is correct but you were correct in the first video. You're on TDC, timing is good and mechanically sound (no broken cam), you have air in the intake, that's it, done. Time for a valve job.
I agree, I'm tired of this one too but I have to show the in cylinder stuff with the Pico. And i t is going to leave questions in our minds about whether or not the valaves are really the problem. I should have combined this revisit with the Pico captures.
I've heard that is dangerous too. But he didn't apply low pressure slowly, he applied the full 100psi all at once. I really don't understand how to keep the piston from moving since you can't hold the wrench on it. With a manual you can put it in gear and use the parking brake. Not sure what you can do with an automatic.
Hi. Just wonder if you can tell me what the problem is with my engine. cylinder 3 has only around 25 psi. And the rest 160 psi. The engine is tuned up from 150 hp to 280 hp. And the spear plugs is dry and werry white. Hope you can respond. Thanks from Norway.th-cam.com/video/YlJduTNkIRQ/w-d-xo.html
That was coming from the crankcase right? That would be an issue with the piston and or rings on that cylinder. Not a good thing my friend. You're probably talking about a complete tear down of that engine.
Thanks for your responds, sir. I think I have to replace the engine. I have tune this 2.0l from 150 hp to 280 hp and 400 nm. And since the spark plugs is white. The engine has got to lean on gas. So shit happens. :) Have a nice day.
Glad you liked my tip! That works on all motors, and the more centered you are on piston dwell at TDC, the safer you are against the crank suddenly rotating on you. I try to estimate the middle of dwell, and that IPA TDC finder helps me to a bit.
Bore wear is usually greater near TDC, so measuring at the top can be important. Head gaskets are above the piston, so there is no concern about blocking the air pressure from escaping out the head gasket at TDC.
The ideal air pressure is 100 psi, because it makes the math easy. The left gage reads how much air pressure goes into the bore. The right gage measures the pressure remaining in the cylinder. So that right gage is only dead accurate if the left gage reads 100%. Otherwise it's reading a percentage of a percentage!
The OTC leak down tester has two gages that both read psi, and it includes a chart that converts the leak down % when using lower air pressures. That snap on gage is nuts if it thinks a 40% leakage rate is anywhere near acceptable. 15% would definitely indicate a problem!! At 40%, you have major blowby or valve sealing issues.
You might also want to start the test at 0 psi on the regulator, and slowly increase the air pressure to 100. Much safer and less likely to rotate the engine suddenly. Otherwise, you had better be at true TDC in the middle of piston dwell. Engine should be warm as well, so rings seal correctly and cylinder bore is oiled up. FYI, piston dwells for probably 6 to 8 degrees at TDC... but the rod is still swinging side to side except when it's right near the middle of piston dwell. Visualize the piston, rod and crank as the rod rotates from one side of the bore to the other.
I did Steve thanks! I would have mentioned your name but I couldn't remember who's suggestion it was, sorry about that.
That's ok. Stay on this case, Paul. We need to find a test that can prove which valve leaks using a scope! Pressure is what leaks, so pressure must be how to find it. Probably at cranking speeds. Although at this point, it seems like the leak down test is still king.
We could try splitting a shop air hose into two, both regulated to 100 psi, one going to the cylinder and the other going to the gauge. It would effectively be a scoped leak down test. Somehow, an in cylinder pressure transducer at cranking speeds would have to show something. I'm hopeful about the map or exhaust pressure sensor too.
To ScannerDanner!!!!!!!!
It doesn't matter if it is a V (or W) engine, a boxer engine or an inline engine .. any piston and con-rod combination will have a point at TDC and BDC where the forces is directly inline with the throw of the crankshaft.
Those two points during a crankshaft rotation is where the piston will come to a complete stop before changing the direction of travel, it is therefore also called a reciprocating engine. To be more specific the engine you are working on is a:"4-stroke Otto cycle reciprocating heat engine".
Thus at TDC or BDC... ANY force exerted on the piston will NOT result in any torque transfer, and thus NO rotation of the crank.
Again this also means that the maximum transfer of mechanical energy from the combustion of petrochemical energy (NOT an explosion as some wants to call it) is during the combustion stroke where the con-rod is perpendicular/orthogonal to the throw of the crankshaft.
Remember "force times arm equals torque"... at this point the "arm", which is the throw of the crankshaft, is at its optimum position, and the force transferred perpendicular/orthogonal from the con-rod is using all the energy to turn the crankshaft.. therefore this is where the max torque is transferred.
SUBSTANTIAL Sir ScannerDanner
Thank you for sharing what you know with us great tutorial brilliant video I enjoy watching video From the start to finish. God bless you and all your family around you Sir ScannerDanner
From Nick Ayivor from London England UK 🇬🇧
BTW. As others have mentioned you should NEVER try to hold the wrench. Simple math (pi x r^2) for a 3" bore and 100psi will tell you that there is about 700lbs of force on the top of the piston and that's further multiplied by the stroke of the crank SO you're looking at a broken hand (as you almost found out). Putting the a standard xmission car in gear doesn't always work either. I've had the car move. If you must test at 100psi then maybe a long wrench jammed against something would make sense.
I use my cock to hold mine down
Good stuff as always man. I was actually surprised at how much controversy there was about a leak down test during this series lol. Back when I was a second year apprentice at trade school (here in BC, Canada, second year is focused on engines, rebuilding, diag, maintenance etc etc) we were taught to always do a leak down test at TDC for more accurate results and safety, but to do it at BDC after just as a secondary test to reveal any issues with a head gasket that might have been missed due to the piston covering the sealing surface at TDC. I always thought this was a pretty "textbook" test lol :) For better or worse, we learn new stuff everyday thanks to the internet :)
Great videos, in my experience doing leak out tests I have found that normal engines that have average wear are always about 10 to 20%..... 25% is a borderline time to overhaul, and 30% is need to repair now and usually a misfire or poor driveability issue has brought the car in for diagnosis.
11:15
I dont think a V type engine would be any different. As long as the connecting rod is perpendicular within the cylinder to the crankshaft it should stay.
Testing with piston down btdc should test for cylinder wear as well as a cracked cylinder wall. Also I use a vaccum/ fuel gauge to check when I don't hear a leak by ear. You can check for exhaust valve at tail pipe, intake valve at vaccum hose, crank case at dip stick tube, and head gasket at the radiator cap. This way you check all possible points for secondary leaks. I use smoke adapters to plug the snorkel and access tail pipe while using one of my assortment of rubber stoppers with one hole in them for the radiator. Btw these stoppers work great sitting on the p/s pump to pull vacuum to remove air from system.
I usually have the leak down tester set at around 25psi input and around the same on the reg so when I turn the crank to find TDC when the hold down gauge begins to rise it's coming to the top.
The lower pressure makes it easier to turn the crank,TDC is easy to judge,if it's not then it spins the crank.
Then dial up 100 psi on the input,
Saves all the screwdriver down the plug hole process.
a timing chain, guides and tensioner can give you that problem with poor sealing valves, timing correlation, misfire, lean condition are also symptom related to a loose timing chain. great videos, keep it up.
Damn and just when I thought I was starting to get it you throw a curve ball.
Great video! Loved the cylinder comparison and different techniques. Just wondering about the t body. Always learned to never physically move the plate on a drive by wire setup.
I really was curious about that T body man. Is it okay? And if so why? Obviously I’m missing something. I’ve learned more from your videos than anyone else. Including automotive class instructors. I think you have said not to do that yourself So, let me know! Just need that knowledge!
I need to review d leak-down procedure. Haven't done it in awhile. Look like a good tool u got there
A note on bdc vs TDC numbers. When I was in school in we would bore gauge cylinder wall wear... The top of the cylinder always read a larger bore than the bottom. I'm talking specifically about in line 6 engines here. It was only a few ten thousandths but it was noticeable. This also accounts for the common cylinder Ridge that can be felt in the liner at the top of the stroke, I've never seen a ridge in the bottom of the liner. I guess the thought is there is some cavetation taking place near TDC as the crank rolls over and shifts the direction of the connecting rod. This also happens at bdc but the piston is closer to the crank and under no pressure at this point. Just a thought as to why you're getting different % of leakage @ TDC vs bdc.
For sure! Thanks
I have been watching all your videos including your premium channel and I have never heard you say anything stupid, until now :) Sorry, but I have to correct. Regardless of the engine type, TDC is TDC and the crankshaft centre line is straight up and down regardless of the engines design. V type or inline. V type just happens to be on an angle but the centreline is still straight up and down.
Can I also say that doing a leak down test at various points of piston position in the cylinder especially if you are chasing a blow by problem is always a good idea. A scour in the cylinder does not always run the full length of the cylinder and a crack in the cylinder may be horizontal. I have seen this in race engines that have suffered serious detonation where it would appear the engine is trying to pull itself apart and a leak down did not show up with the piston at TDC. Wind the engine down a inch and bingo.
Love ya work Scanner Man
Took my stepson's H3 to the dealer today for a check engine light, got a 0300 code and they said cylinder 3 misfire. Paid $200 for troubleshooting and they said the cylinder gets 160 psi (good), and the problem is leaking (down-leak?) into the crankcase, replace the rings. They suggested replacing the engine for over $9k, rather than rebuild the engine . We replaced the plugs with platinums (the installed plugs were roasted), cleaned the MAF and Intake, got a new air filter, got a full syn oil change and added 6 cylinder Restore Engine Restore. Have full system fuel injector cleaner to put in next fill up. Check engine light is still on, though only 3 hours later. Vehicle wasn't acting up , so no difference in performance since light came on. WHAT ARE YOUR THOUGHTS ON OUR SITUATION AND WHEN SHOULD THE CHECK ENGINE GO OUT, IF WE HAPPENED TO FIX IT? Thanks so much for your great videos and your time. Much appreciated.
I've seen leakdown testing done with different incoming pressures (usually lower). Is there an optimum intake pressure for the most accurate test? Presumably doing it with lower pressures might be a little safer....
Here's a clip of the one that I use... th-cam.com/video/aKwWCAlNRlg/w-d-xo.htmlm21s
as pressure builds, you can see that the the "leak" side follows quite quickly from low to higher pressure. I think any where from 50 to 80 psi should be enough to find leaks. Obviously no leak in my video as I am just using the air to hold the valves closed.
I noticed in several shots that the input side pressure dropped off the initial 100psi set point to about 90 or less. Wouldn't it be wise to set that back to 100psi. That pressure affects the leak down gauge side measurement as well. It might make the difference between the gauge showing in the good or marginal range and change your opinion of the result. This is why I prefer the type with two regular gauges and look for the difference between them.Sage
Hi Paul, well I think what ever kind of engine it is the con rod and crank will all be in line at TDC, just one comment, when you do this with a Manual Transmission car you can put it in top gear with parking brake on to stop engine moving, I guess a lower reading at tdc prob means the bore is worn a bit at the top, I don't think valve overlap would come into it for quite a lot of crank travel, with the old distributor cars you can see what cylinder you are on by checking where the rotor arm is pointing roughly..cheers good video, I think you would only need to put oil down the bore if you were getting pressure out the oil cap - Fred in England
Good stuff- I do like the use of the MAP wave form and look forward to pico pressure transducer wave form, since the two are so much different it would be interesting if we could view the WPS500 wave form and be able to interpret the MAP wave form consistently.
I have the in cylinder readings on the pico coming up next. If I can I may use the WPS500 on the intake and maybe my fluke pv350 in the cylinder?
Depends on what else is going on. It would be cool to see. I want to get a first look sensor in the tailpipe too but do not have one yet. It would be super cool to see all three.
Usually when an engine overhaul is done, the top part of the cylinder needs to be reamed to get rid of a ridge. If ridge is not removed the rings will expend and it will make the removal of the piston hard and it may even break the piston.
Long story short, the top of cylinder walls wear more than the bottom part. That could be the reason for air escaping more on the top dead center from the rings. On the bottom, the cylinder is less worn and the rings seal better.
a coworkers case scenario ...basically followed these instructions on a 4 cyl. Toyota Rav 4 .... also had big leak out of the intake clinder 4...after teardown no problems found with valves...but tech was instructed to replace head and valves...warranty .... after put together ... still had a air fuel ratio imbalance on #4 ... removed valve cover... redid leakdown visually seeing the cam lobs were off the valves...leakdown did reveal leak out of crank case... NOT intake.... i would definitely recommend leakdown down with valve covers off instead of on... a broken piston was found on complete teardown.... just my opinion.
swillieboy so maybe the key then is to remove the pcv and breather lines to be sure it is not coming from the crankcase. this should fix that variable. great tip! thanks!
Mike P that's exactly what I was thinking,would it be an idea to perhaps remove all spark plugs prior to test ?
didnt quite heard,you said with ring problem in engine,we dont see any smoke from tailpipe?
Thank you paul great videos.
@4:21, does the thermostat have to be open to see air bubbles in the radiator from a leak down test with a bad head gasket?
Sandbag1300 NO air will get around it.
I'd like to see a secondary ignition wave form and look for hash on the spark line which would indicate valve sealing issues. Would this be possible?
THANX
Always great content Scanner Danner appreciate the time and energy you put out. If you guys want to save money and learn how to build a leak down tester watch my "MAKING A CYLINDER LEAK DOWN TESTER AND CHECKING ENGINE INTEGRITY, PISTON RINGS, VALVE & SEAT SEALING" its simple.
nice! thanks for that
Hey I watch your videos too!!
Why didn't any of the valves open at BDC because of valve lead or lag, depending which way the engine rotated? I don't know cam spec for that engine but I assume the exhaust valve would have opened before BDC. Did you not allow the piston to go all the way down to BDC with the wrench? Great videos by the way.
Just curious as to how much shop air pressure you actually need to make the test accurate? Would be a lot easier to control the crank with 40 psi than 120 psi for example.
Here is instruction on a harbor fright compression leak down tester:
"NOTE: Set the air compressor’s regulator
to 7 to 100 PSI. Never operate this
tester with air pressure set higher than
100 PSI, which can damage this tool."
Not sure if 7 psi is enough to even move the crank.
Hi Paul, sorry to resurrect such an old video (great series btw) but i am now personally starting to play about with a pressure transducer and a first look sensor so was wondering if you could share where you personally went for information regarding how to disect these waveforms? I know this is 5 years old now but at this point you were just starting to get to grips with this and i was wondering if there was a particular website or training book that you found useful on how to understand and interpret what you were looking at on the screen. Thanks as always
Dave
Good information. Are you going to show any video with the cylinder head removed? Just curious
That is the plan, hopefully we can see something.
great job. mr danner
GMC TSB# PIP4013C: In-line Truck Engine Misfire at Idle.
Important: Before replacing the cylinder head, review the latest version of PIP3940, I forgot to mention this is a recall. you must change the entire cylinder head, what is bad are valve spring. the new head got this fix.
you always have some ring blow by cylinder wear is less at bottom of the cylinder than at tdc when you tear down a motor you always find more ridge at the top of the cylinder than at the bottom. leak down sees the extra wear at tdc and adds to the leakage. best to do test at bdc once then add oil to check for the amount of leakage added to leak down by ring wear.
Would it be true to say that running the compression test at TDC and then lower in the bore at different points be a good indication of bore taper wear ?
It is normal to have more wear near TDC as this is wear all of the major psi occurs in the cylinder. What I do not know is what is an acceptable amount. This is not my area of expertise.
ScannerDanner Maybe a good investigation for a future video ? Would be cool to see if that would work.
Hey ScannerDanner, I have a car blowing blue smoke and has misfires, I did a cylinder leak down test and found 45% leak on cylinder 2 and found air coming out of cylinder 4 any idea what this indicates? Thanks
blue smoke is burning oil and that is a huge amount of leakage, I worry about a ring issue but that wouldn't cause air to come out of the #4 unless the rings are bad there too
What are your compression pressures on all cylinders?
Putting a ratchet on the crank would be a lot safer because you can still apply pressure but if it wants to take off on you it wont fling the wrench and hurt you.
I like to turn into tdc by hand and hold it while noting force... Built in torque wrench on arm.. bionic mechanic man...
what percentage of leak down will be aceptable, I know comparing cylinder and highest will be the bad, but wear off even engine ??
i think it's like 10%
Your mostly looking for a difference between cylinders. The average leakdown of more than 35% would indicate time to consider an overhaul.
Assuming your as cheap as I....
what happens when you have a blown head gasket to an adjacent cylinder and that cylinder has either the intake or exhaust valve open? would this not throw off the test? of course you would see this ounce you remote the head anyway.
Mike P For sure there are tons of variables with in-cylinder pressure waveforms. I would think you would catch this one easily on a relative compression test as pretty much two dead holes.
what if the cilinder comunicates to the neighbourg cilinder and loses presure through the intake valve of the neibourgh cilinder, valve that is normal to be opened in that moment.
IIRC believe you then could hear air coming out the spark plug hole of the adjacent cylinder.
what was the fix ? with this one
@ScannerDanner that radiator water looked oily ??
Probably radiator has hole mixing with the oil ??? I'd the oil lines plug to the radiator
Latex or rubber glove over intake.
Scanner and Students:
I hope we get to see the dis-assembly and repair of this Hummer engine.
More good stuff that TDC trick works on boxer style engines also. I'm a old vw guy. Porsche and Subaru
Can’t believe Snap-On uses the idiot gauge. That’s pretty funny.
Can fuel in the cylinder keep my mustang from starting
If the engine is flooded, yes, but you'll need to find out why it flooded
@@ScannerDanner today I did added oil to all the cylinders in my mustang and it started up!!! I have a dead miss on cylinder #2 cylinder leak tested and it's coming out the oil filler and throttle body. Also smoke tested through the spark plug hole #2 and smoke came out the throttle body and oil filler hole. So my guess is it needs rings. Time to sell
You’re doing this test wrong. You do not pressurize the tester then plug it into the cylinder. You have everything connected all the way to the cylinder and then turn the tester up until the first gauge reaches 100 PSI, then you read the second gauge to get your percentage of leak down. Almost every video on TH-cam on how to do this test is wrong. It’s freaking ridiculous. Lol
it was still accurate in what we showed, even if I used it wrong
how long does your class last as in weeks?
8 weeks, 5 days a week 6 hours a day.
wow. i want to but just cant due to work. i did buy your book a few weeks ago. very good work. u do autographs?!... cause one day your gona make it big with these vids
philbfree1
lol thanks!
were should i start a diag on a p1131 trouble code? i was thinking vacuum leaks,then fuel pressure then injector balance test.
yea i was watching your fuel injector videos of them being stuck closed and open. would your old vantage graphing meter? be adequate enough to capture the pintle on the injector waveforms? im looking for something cheap and that looks older and probably cheap enough
just want to add a comment, my leak down tester instruct not to apply anything over 80 psi to the inlet leak down tester, that might keep from crank turning while doing the test, or might b my leak down tester is a cheap one lol.
for sure the higher the psi the more likely it will push the piston down in the cylinder
Part 4? I understand it's a great learning experience for your students but compared to all of your past videos it seems like you're going overboard on your leak down results. Yeah it's the company vehicle and you want to ensure you're diagnosis is correct but you were correct in the first video. You're on TDC, timing is good and mechanically sound (no broken cam), you have air in the intake, that's it, done. Time for a valve job.
I agree, I'm tired of this one too but I have to show the in cylinder stuff with the Pico. And i t is going to leave questions in our minds about whether or not the valaves are really the problem. I should have combined this revisit with the Pico captures.
So watch Part 5, I am uploading right now and you will understand why I shot part 4.
Never ever put air in with the damn wrench on. Especially don't hold it. Good way to brake your dang arm. Low pressure applyed slow saved u.
I've heard that is dangerous too. But he didn't apply low pressure slowly, he applied the full 100psi all at once. I really don't understand how to keep the piston from moving since you can't hold the wrench on it. With a manual you can put it in gear and use the parking brake. Not sure what you can do with an automatic.
I wonder what a smoke machine test would reveal....
my brother you sound like is the firs time you ever done this thing I couldn't watch the whole video
If this is the only one of the series you watched I can see how you would say that. You need to watch the whole series.
great
Hi. Just wonder if you can tell me what the problem is with my engine. cylinder 3 has only around 25 psi. And the rest 160 psi. The engine is tuned up from 150 hp to 280 hp. And the spear plugs is dry and werry white. Hope you can respond. Thanks from Norway.th-cam.com/video/YlJduTNkIRQ/w-d-xo.html
That was coming from the crankcase right? That would be an issue with the piston and or rings on that cylinder. Not a good thing my friend. You're probably talking about a complete tear down of that engine.
Thanks for your responds, sir. I think I have to replace the engine. I have tune this 2.0l from 150 hp to 280 hp and 400 nm. And since the spark plugs is white. The engine has got to lean on gas. So shit happens. :) Have a nice day.
hello sir..may I know what is TDC..please?..thanx...
Top Dead Center. It is the piston right at the top of the cylinder.
Dan you one crazy sob.
Typical inline GM motors smh. Valves are garbage. I just bought a leakdown tester bc of one if these 3.7 bummers.
I need to review d leak-down procedure. Haven't done it in awhile. Look like a good tool u got there