Compression/Leak Down test DONT MAKE THIS MISTAKE!

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Make sure to set the tool gauge back to zero when doing the test!
#leakdowntest #engine #compressiontest
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The content of this video is available for informational and educational purposes only. It is not intended to be a substitute for the professional advice of a mechanic who has personally inspected your vehicle, nor does it create a relationship of any kind between the CM Autohaus and you. Every situation may be different, and CM Autohaus does not make any warranties, whether express or implied, as to the accuracy, fitness, or applicability of the information or automotive parts portrayed in this video to any project and makes no guarantee of results. CM Autohaus and any sponsors of this video will not be liable for any damages related to personal injury, property damage or loss of any kind that may result from the use or reliance on this video and/or any automotive parts represented in this video. You are using the information and automotive parts portrayed in this video solely at your own risk.

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14 июн 2022

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Комментарии : 104

@CMAutohaus 5 месяцев назад

Make sure to set the tool gauge back to zero when doing the test!! My Mistake!

@lancejonesmusic 5 месяцев назад

Awesome guide dude! Clear, professional and precise, detailed video. Much appreciated!

@veehaw85 6 месяцев назад

If a wet and dry compression test will give false results why not just do the leak down test from the get go?

@bigstuff52 Год назад

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...

@CMAutohaus Год назад

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

@jooper99 Год назад

Only way I've ever done it. Never made sense to me to hunt for tdc.

@johnparson9573 10 месяцев назад

Fantastic job. Love your explanation on everything. Keep up the great work brother!

@CMAutohaus 10 месяцев назад

Much appreciated. Thank you for the kind words

@alanlaing673 13 дней назад

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

@troyc333 11 месяцев назад

And don't forget the shop dog. Very important to have the little boss running around making sure the work area is safe.

@CMAutohaus 11 месяцев назад

100% agree!

@oppanheimer 11 месяцев назад

Very demonstrated and explained, thank you.

@juanga69 2 года назад

Great video! Helpfull as always.

@CMAutohaus 2 года назад

Thanks for the support! Glad you found this video useful!

@gregorymammel6761 4 месяца назад

Dude! this video was extremely helpful. Great explanations of all 3 tests.

@CMAutohaus 4 месяца назад

Glad it was helpful! Thanks for the watch!

@MarzNet256 4 месяца назад

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,

@pyt22fr11 8 месяцев назад

Excellent presentation !

@francisdsa6790 Год назад

Appreciate your testing method of compression of engine and demonstration thanks brother Greetings 🙏💐

@gee3883 5 месяцев назад

Brilliant explanation dude.

@johnlucala1532 Год назад

Great video,and very important topic,I just subscribed to your channel, right now...

@CMAutohaus Год назад

Glad you found this vid useful! Thank you for the sub!

@CelicaDreams 2 года назад

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.

@CMAutohaus 2 года назад

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.

@michaelyount3176 3 месяца назад

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.

@kd6tas 9 месяцев назад

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 RU-vid videos. This was one of the better ones.

@jeffallen6937 14 дней назад

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.

@salvadorpalma8173 Год назад

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.

@solarchild1 8 месяцев назад

great info been used on every aircraft engine since ww2

@kennethmabus381 Год назад

Nice video!

@CMAutohaus Год назад

Thanks for the watch!

@SolarMillUSA Год назад

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).

@ghj1502 Месяц назад

High praise!

@TorxGarage Год назад

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.

@ruthdanielson919 Год назад

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.

@CMAutohaus Год назад

Glad you found this video useful. Sound like an internal engine issue if there is coolant loss and no external leak.

@ruthdanielson919 Год назад

@@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.

@RyuMoto 2 месяца назад

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?

@CMAutohaus 2 месяца назад

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

@BatJordo 9 месяцев назад

You hear it in the oil filler because of the Positive crankcase ventilation valve.

@garrettwalraven2552 Год назад

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 😊

@JoseGonzalez-ew6zz 3 месяца назад

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

@JoseGonzalez-ew6zz 3 месяца назад

I didn’t know how to do the leak down but I’d like to do it

@Suar5379 8 месяцев назад

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

@florenbaron7111 18 дней назад

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.

@Flatlower 2 месяца назад

Cummins recommends checking on TDC. You can get a false reading otherwise. You wear is on top end of the piston liner.

@cagr0311 Месяц назад

Do u take all plugs out or one at a time

@MeanDaGreenScreenBra 8 месяцев назад

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?

@tl-ec4pl 2 года назад

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?

@CMAutohaus 2 года назад

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.

@chasereeves8977 Год назад

How did you get the Hks oil splash pattern on the valve cover? That’s sick!

@CMAutohaus Год назад

Painted myself. Each color is a different layer masked off. I think you can hydrodip these days - much easier

@Priest 11 месяцев назад

@ 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"

@CMAutohaus 11 месяцев назад

Yes I made a mistake, needle needs to be calibrated everytime this is done.

@jantelow 5 месяцев назад

How to test oil rings ?

@badbug911 9 месяцев назад

Which model snapon leak down tester is this.

@squaresquare5883 5 месяцев назад

what size is your compressor

@dinto_louis Год назад

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

@CMAutohaus Год назад

I'd do a leak down test. Something may be wrong with the head or head gasket

@trevormorgan7138 Год назад

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.

@114bdjensen13 Год назад

Ur confused with each test

@richardpope9985 Год назад

Great observation.

@RAWRMotorsports 3 месяца назад

How much u charge for all 3 tests per cylinder ?

@ceezauto213 8 дней назад

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?

@CMAutohaus 8 дней назад

There could be a unique way you have to bleed the system

@ceezauto213 3 дня назад

@@CMAutohaus thanks still no luck though

@S7RING3R 2 месяца назад

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?

@andiminthegarage7081 9 дней назад

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.

@Drew.407 2 месяца назад

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?

@CMAutohaus 2 месяца назад

Very Low compression in one cylinder

@Drew.407 2 месяца назад

@@CMAutohaus oh dang. Even if the number is good relative to the others?

@Villagerbluewheelsunflower Год назад

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?

@CMAutohaus Год назад

Depends on the tool. I've seen others like OTC spec a different pressure

@wholewheat1 7 месяцев назад

Leak down percentage is calibrated to 100 psi because the math is simple. 100 psi in - 95 psi out = 5% leak

@silicondt1 Год назад

When you do compression and leak down do you leave all spark plugs out or put them back in as you go?

@CMAutohaus Год назад

Leave them all out the entire test

@bradleywesterford3587 2 месяца назад

couldn't you just have pulled the EFI main to disable the fuel system instead of unhooking the fuel pump?

@R3ddyyg 10 месяцев назад

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?

@CMAutohaus 10 месяцев назад

Leaking valve stem seals should cause smoke to come out the exhaust on hard accel or decel.

@R3ddyyg 10 месяцев назад

@@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 🤣🤣

@dennissytsma3561 Год назад

I agree with what you said, must do all 3 tests. Do you like to do compression test at normal operating temperature? Nice video.

@CMAutohaus Год назад

I go by the FSM. They differ between engines ie S2000 Honda wants you to perform the tests on a cold engine.

@stephenburnage7687 10 месяцев назад

@@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.

@limamantapachitas 3 месяца назад

I would do it when the needle spikes for 3 time

@3gcraftsman 5 месяцев назад

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?

@CMAutohaus 5 месяцев назад

15 psi isnt much. Id do a leak down and see where the compression loss is comming from.

@3gcraftsman 5 месяцев назад

@@CMAutohaus thanks

@PeterHernandez-lg2eh 4 месяца назад

Leakdown covers it. Smoke for vacuum pressure for coolant ,leak

@jimlamb5508 Год назад

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

@CMAutohaus Год назад

When I get a "bad" test I'll make sure to film it. Thank you for the feedback!

@SolarMillUSA Год назад

@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.

@UpInSmoke54 6 месяцев назад

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.

@RAWRMotorsports 3 месяца назад

Compression test should be done on a dry cold engine

@TBD3.0 Год назад

👍🏻

@never2enuf Год назад

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".

@dalebabbitt6185 9 месяцев назад

Curious, what was incorrect? Thank you.

@DidiLeeReco 5 месяцев назад

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.