Compression/Leak Down test DONT MAKE THIS MISTAKE!
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- เผยแพร่เมื่อ 14 มิ.ย. 2022
- Make sure to set the tool gauge back to zero when doing the test!
#leakdowntest #engine #compressiontest
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Make sure to set the tool gauge back to zero when doing the test!! My Mistake!
That was only one of your mistakes.
If a wet and dry compression test will give false results why not just do the leak down test from the get go?
Awesome guide dude! Clear, professional and precise, detailed video. Much appreciated!
Excellent presentation !
Very demonstrated and explained, thank you.
Appreciate your testing method of compression of engine and demonstration thanks brother Greetings 🙏💐
Great video! Helpfull as always.
Thanks for the support! Glad you found this video useful!
Fantastic job. Love your explanation on everything. Keep up the great work brother!
Much appreciated. Thank you for the kind words
I make a positive stop out of an old spark plug. Length is set so that when the cylinder you're testing is at TDC, 2 of the other cylinders are at BDC. So, if I'm testing #1 at TDC I screw the stop into cylinder #2 or 3. This locks the engine into place. I don't have to worry about wrestling a wrench to hold it in place. And I can check for noise/leak presence by myself. Also, I close up the garage and turn anything off that makes noise - so I can hear where the leak is coming from. I usually pull the dipstick and stick a piece of tubing in it. Easy to listen to the exposed end of the tube for crankcase noise. Easier to listen to throttle opening on leak down if you pull your screw driver and leave it closed - you'll get more audible noise if you have a leaky intake valve.
Brilliant explanation dude.
Really awesome video. So, three final numbers per cylinder and a description of leak down. I just love it when someone knows what the hell they are talking about,
Need to set the regulator before plug in to cylinder, set the psi in and then turn till it goes as close to zero (set) as possible then lock the regulator, then you can plug in to adapter in the cylinder , you put in 100 psi and it shows up 70 or moderate on the second gauge, you have a 30% leak so to speak ,also each cylinder tested should be at tdc before adding air as the engine could spin and if you have a bar on the crank well good luck ,. Also listen for noise if it’s out the exhaust or the intake air pipe then it’s the valves, if it’s out the coolant it’s your gasket and if it’s out the oil filler then it’s either the block , the liner, the piston or the rings . that’s how I was taught and works for me
Excellent info as always! I did compressions/leakdown tests on an imported engine with unknown history on the stand a few months ago. This will help me sleep because I doubted my process a bit as I was seeing 0% leakdown on two of the cylinders which I figured was impossible as there will always be some leakage past the rings. Unfortunately I had leakdown out of the exhaust side on cylinder 4 and haven't had time to dig in to see what's going on. At least I know I can trust the results.
Glad you found this useful! Yes 0% is ideal, but even with 0% on the gauge you will still hear air come out the oil filler as "true" 0% is impossible.
High praise!
I've been doing automobiles for 48 years..I never thought about rotating the engine till it gets hard to turn...great vid..Pleasure subscribing to your channel...
Hey! Glad you found this video useful. I am thank for the the people who have taught me my trade and I am happy to share my knowledge
Only way I've ever done it. Never made sense to me to hunt for tdc.
Dude! this video was extremely helpful. Great explanations of all 3 tests.
Glad it was helpful! Thanks for the watch!
Great video,and very important topic,I just subscribed to your channel, right now...
Glad you found this vid useful! Thank you for the sub!
great info been used on every aircraft engine since ww2
And don't forget the shop dog. Very important to have the little boss running around making sure the work area is safe.
100% agree!
This is a bit random but don't forget to drain the mioster from your air compressor. Underneath the tank you will find a little drian valve. The valve typically needs to be replaced.
Nice video!
Thanks for the watch!
Good information, would like to note you need to make sure you set the regulator to 100psi before connecting it to the cylinder. I like to recheck it each time. In the case of a Mini engine, 9% leakage is enough to cause smoking and ultimately condemn the engine. I would suspect this is why you’re getting such good readings. But still very useful information.
There will always be some leakage into the crankcase because piston rings have gaps.
Also, it's best to do the leak down test with the piston at top-dead-center because the top of the cylinder is where the most wear takes place. In other words, the leakage will be highest with the piston all the way up. An engine with a lot of wear can have a difference of .020" between the top and bottom of each cylinder. That was more common in old-school engines with cast iron blocks and nothing done to slow cylinder wear.
To help keep the piston at the top during a leak down test, start with the supply-side air pressure at zero and bring it up smoothly.
I've watched a number of leak down test TH-cam videos. This was one of the better ones.
5% is incredible, not just fine. You *should* have some leakage, and it should be around the piston into the crankcase (just as you heard).
This guy: "If you don't do wet comp. test the results are rubbish"
Also this guy: "For the sake of time I'm not gonna do a wet comp. test."
Alright mister expert.
He explained why, all were really close.
I've had it happen twice now in a 43 Vortec motor and the last time it happened I now have zero PSI in cylinder 4 which I'm praying is a valve and not the cylinder
Excellent. Very helpful. 2006 tacoma with disappearing coolant. Leak down test. All 0% except valve #2 at 5%. No bubbles in coolant but did not state where he heard leak.
Coolant continues to slowly disappear no visible leaks. Radiator pressure test 15 psi performed no visible leak at 10 minutes. Lost nearly one resovoir full in 3 months.
Glad you found this video useful. Sound like an internal engine issue if there is coolant loss and no external leak.
@@CMAutohaus Right, but passed leak down test, didn't reveal an internal engine leak. Radiator pressure test while visualizing with boroscope another good test. Can dx drops of coolant at the head gasket. Will repeat radiator pressure test. Hopefully will find a visible leak.
You hear it in the oil filler because of the Positive crankcase ventilation valve.
This is the best I’ve seen. Unfortunately need to do this on my ej207 swapped wrx . I had 110,110,105, 102 psi on mine which is lower than the 125 it should be for a ver8 engine
I didn’t know how to do the leak down but I’d like to do it
One of the best videos on this topic. What's the best way to do a compression test when the motor is on an engine stand?
When the engine is out, we usually do compression tests when the engine is on the floor for saftey, also because we need to installed the starter and bellhousing at times. We just hook up the starter straight to a battery and crank 8 times
Cummins recommends checking on TDC. You can get a false reading otherwise. You wear is on top end of the piston liner.
How did you get the Hks oil splash pattern on the valve cover? That’s sick!
Painted myself. Each color is a different layer masked off. I think you can hydrodip these days - much easier
Hey brother quick question if that’s ok did dry test two cylinders at 135 (1 and 2) and 185 (3 and 4) wet test (1 and 2 ) when up to 185 problem with the block…? But what are the chances to be rings only….? Car over heat I did the head gasket leak test was 100% good nothing on the radiator the car is a mini 2011 1.6 nine turbo. Thank you
Why do you need all 3? Seems like a compression test can yield good results even when there is a problem (false positive or negative? I can never remember which). What does a compression test tell you that the leakdown doesn't?
So my 97' honda odyssey with 320,000 miles has upper and lower radiator hoses only a year old that collapse. Then the radiator empties to about a 3rd to a 1/4 coolant bottle low but while the overflow reservoir is full and overflowing at the same time and Pisses on the ground. There is rusty like sediment in the radiator and only the new cap I put on and its a tiny bit cloudy. I think this is original radiator from 1997 but I don't know it's a single one owner before me. Is my head gasket leaking or should I just overhaul and get new hoses (entire engine) new radiator, thermostat, housing,temp sensor and water pump or what? Much appreciated of anyone's help thanks 😊
Hi CMA! Thanks for this video been trying to purchase a 20v BT but a lot of engine importers tell me they can only do the compression test after payment and they cannot do the leak down test when an engine is outside of a car. This been holding me back from purchasing. Do you know of any 20v BT engine importer that can do all the things you've mentioned in this video that can ship to Washington?
I do not, but that sounds pretty bad on the engine importers part. We do compression/leak down on engines outside the call regularly.
Also have had customers buy engine with a compression/leak down sheet attached.
I think 20v engines are so in demand these days, importers dont even need to bother with a comp/leak down because people will pay up the arse reguardless.
Do u take all plugs out or one at a time
How to test oil rings ?
what size is your compressor
Which model snapon leak down tester is this.
re the air compressor, is there one that is good for mechanic work as well as body? i intend to use it at home. I tried to use a small huskey but it runs out of air too quickly
@ 8:30 is that really how you perform leakdown test ?
I thought you need to calibrate the needle so its right at the beginning of "set"
Yes I made a mistake, needle needs to be calibrated everytime this is done.
How much u charge for all 3 tests per cylinder ?
Great video. I'm wondering if you can help me out with some advice. I've done so much work on this car but it still overheats. (2012 ford fiesta 1.6l)
I bought the car with the engine overheating and blasting white smoke out of the exhaust. with the coolant bubbling in the reservoir. I have since, replaced the head gasket, coolant outlet gasket, thermostat, water pump and resurfaced the cylinder head with new head bolts. And properly bled the cooling system.
The car still performs the same after all of these repairs. The car still passes the engine block test (same as before the repairs). And there was never signs of coolant in the oil or oil in the coolant (before or after the repairs).
A compression test determined cylinder 3 had 120PSI and all the rest of the cylinders were around 110PSI (I was told by a dealer tech that the normal range was within 100-110PSi). All of the coolant hoses get hot and my heater blows nice warn air. There are no coolant leaks and the system holds pressure at 13 PSI for 10 minutes without falling down. The car idles perfectly.
Why is this engine still overheating? Is it possible to have a cracked cylinder head/engine block even with a passed block test and good compression?
There could be a unique way you have to bleed the system
@@CMAutohaus thanks still no luck though
I agree with what you said, must do all 3 tests. Do you like to do compression test at normal operating temperature? Nice video.
I go by the FSM. They differ between engines ie S2000 Honda wants you to perform the tests on a cold engine.
@@CMAutohaus I was taught that the cold test is the more accurate. As the air gets warmer, the pressure increases (Bolyes law). Also, metallic components expand, closing metal to metal gaps. A cold test is therefore the purest test but there is no reason why you cannot undertake both cold and warm tests. There is a YT video of someone who had good readings on all cylinders on the warm test but had one cylinder seriously bad, at only 70psi, on a cold test, indicating the early onset of a problem.
When would you do a leak down test at UNDER 100psi? Smaller engines? Different types of leaks? Snap-on was designed for 100psi testing only. Other companies can test at lower pressures. Is there a point?
Depends on the tool. I've seen others like OTC spec a different pressure
Leak down percentage is calibrated to 100 psi because the math is simple. 100 psi in - 95 psi out = 5% leak
Your readings weren't zero. You have to adjust your regulator it was above 100% after hookup when cranking the engine over. Cranking the engine on compression back feeds through the restrictor on the gauge and adds pressure to the regulated side. Your first gauge is regulated pressure, your second gauge is after a restrictor and is simply observed pressure. Since your regulated pressure changed you have to subtract your observed pressure from the new regulated pressure. Zero percent is actually not realistic, there will always be leakage... You just saw zero because you messed up the gauge by cranking the engine.
Ur confused with each test
Great observation.
I would do it when the needle spikes for 3 time
My engine only shakes after warming up. Can someone tell me what it might be? I know there are some smart people here. The vehicle barley moves when pressing the gas, smoke or steam coming out of the exhaust pipe, etc. The water pump went bad and I replaced it. I think I had a blown head gasket. I used gasket sealer and the smoke reduced almost completely but when I first turn the vehicle on a puff of smoke comes out. No check engine light. The temperature guage does not go up enough when my scan tool shows a much higher temperature. The engine is knocking. When I remove the upstream oxygen sensors I hear something like clunking or air quickly releasing from the exhaust valve when it shouldn't, on the side that shakes the most. I would really appreciate advice, suggestions, etc. Thank you.
Hi, the wet reading on one of the cylinders is lower than dry reading..what could be the inference..?
I have done dry & wet compression test on my VW Polo 1.2 TDI..the reading is lower in the wet test than the dry test on cylinder number 3..?
Dry:
1 - 26.7 (Bar)
2 - 26.5
3 - 27.8
Wet:
1 - 27.6
2 - 26.7
3 - 26.3
I'd do a leak down test. Something may be wrong with the head or head gasket
👍🏻
When you do compression and leak down do you leave all spark plugs out or put them back in as you go?
Leave them all out the entire test
Wet compression test on subaru motors, how do you make sure the oil poured into the cylinder coats the whole piston ring? Do I just turn the motor over and that will be enough movement to coat the rings?
Also, is it okay to do a compression test on a motor outside of the car that doesn't have oil in it?
I have a vw beetle boxer engine, and I used a long nosed air gun to move the oil around the cylinder. Seemed to work OK.
Leakdown covers it. Smoke for vacuum pressure for coolant ,leak
You mentioned you were listening to the cranks during the dry compression test to see if a crank is turning over too fast or skip a crank. What would it mean if it did do that?
Very Low compression in one cylinder
@@CMAutohaus oh dang. Even if the number is good relative to the others?
My car is burning oil, but being a Focus mk1 no shop really cares about it, they all have the shop full of suv or more expensive cars... So i decided to do compression and leak down test myself, the compression it's very good and tomorrow i'll do the leak down test, i'm thinking my oil is dripping from the valve stems seals how could i hear it? From the intake? Vacuum line?
Leaking valve stem seals should cause smoke to come out the exhaust on hard accel or decel.
@@CMAutohaus Idk why but i have whitish smoke coming in the cabin on hard acceleration and i notice it on decel on the back, the test didn't show much tbh, 15 to 20 on all 4 cyl, i'm rebuilding the top end in a month and will keep adding oil in the meanwhile... Might be a headgasket.
I'll do headgasket, rings, valve stem seals and more, i have a miata as """backup""" so i can still go to work and get groceries 🤣🤣
Does anybody know what can cause an engine to suddenly start eating spark plugs
Compression test should be done on a dry cold engine
@7:30 0% leak down is not ideal. Because of the gaps in the piston rings and the necessary clearance for lubrication, you will never have a perfect seal. It is so incredibly unrealistic that it means that there is a problem in the testing set up, like forgetting to remove the Schrader valve when combining parts from compression and leak down test kits. A leak down that low should be a red flag 🚩 that something isn’t right.
I think he got 0% because the intake pressure was over 100 psi, if he had adjusted the intake pressure back to 100 psi when the pressure rose on the output he would have had a deffirent result.
If you are going to do a video, use an engine with a problem. It was a good video, but MY ENGINE conclusions were drawn immediately after the wet test. still low compression after oil, leaves only the head whether it is a gasket or valve, the head must be removed. I will do the leak test just for curiosity, but suspect the valves leaking (90%) or head gasket (10%) being left out after a rebuild. (That i did not do) I will not look for the place where both valves are closed either, just remove the rocker arms. dry 90psi, wet 120psi so it must be head related? Leaking sound is LOUDEST at valves, I don't believe i need a leak down
When I get a "bad" test I'll make sure to film it. Thank you for the feedback!
couldn't you just have pulled the EFI main to disable the fuel system instead of unhooking the fuel pump?
I did dry compression and one cylinder was 15psi lower than the rest. I did a wet compression on that cylinder and brought it up to exactly the same as the other cylinders. Anything I can do to improve or just let it ride?
15 psi isnt much. Id do a leak down and see where the compression loss is comming from.
@@CMAutohaus thanks
When I saw that he did the test without setting the tool gauge to zero first on the leaking gauge i stopped watching it.
12 volt system,12 volts is a dead battery...🤔
Approx 12.6v is a full battery. 14.7v is charging system volatge. Some cars wont even start with a battery with 12.0v
Keep looking if you want to accurately conduct a leak down test. This guy's method is absolutely incorrect. The title is correct, "DON"T MAKE THIS MISTAKE".
Curious, what was incorrect? Thank you.
When I saw that he did the test without setting the tool gauge to zero first I stopped watching it. You have to calibrate the gauges before you do any test otherwise will give wrong reading.
lol gtfo. His method is correct
@@snguyn796 then you are a stupid and retard brain! First because the method is not 100% correct second for using inappropriate words.
@@snguyn796can I use this method instead of finding tdc on a v8
Note to self: Don’t use a wrench to tighten the oil fill cap next oil change.
You didn’t zero gauges. So entire video was invalid results sir.