In aviation we do leakdown tests on our engines annually. We do the test at 80 psi, because it's much easier to hold the propeller that way, and you're less likely to get hurt.

@thejollywrencher

3 ай бұрын

I can imagine the force on the crankshaft would be enormous on an airplane engine. Huge bores and stokes compared to automotive engines. Be tough to hold the prop from turning. Especially a gear deducted prop.

@MrTheHillfolk

19 күн бұрын

Oh man ,she's down at 75 over 80, better tear it open.

A key benefit to a leak down test is legacy results over time. Do baseline testing after the engine is built and run in, and at regular intervals, esp a race engine, and also if you start having performance degradation or issues, before you start chasing the chassis or various engine tune variables, do a leak down on the engine. You’ll get a much more precise indication of engine health than you will with a compression test.

A leak down test is a good second test to a compression test. I periodically test and record the compression on my race engines. If one of the cylinders is low, this is a great way to quantify it. You can use the air hold for on the engine spring changes to listen to the engine to help determine where the problem might be without the need of a leak down gauge. I am a tight wad and always try to find the cheap work around. I would certainly use a leak down gauge if I had one, but I rely on the compression check and air hold for now. Great video.

Great video with solid information.

@TotalSeal

3 ай бұрын

Glad you enjoyed it!

I learned in 1968 how to and why to do a leak down test. I remember back then my new friend just out of NAM had his new 67 Mustang 289-271 HP car. It only had 6,000 miles and we were hungry to learn so we leaked his 289 it was even all 8 cylinders @ 22-23% we were like what? Compression was even too all 8 I don’t remember but 165 psi sticks in my mind but anyway we took it to the Drag strip and ran 14.23@ 97-98 mph. Which was ripping in 1968. So never worried about Leak down for many years. Trusted compression and balanced cyl to cyl. Live n learn. M

@billshiff2060

3 ай бұрын

Was that a snapon tester? cus they are grossly inaccurate as are almost all testers that use 1 gauge.

Troubleshooting a po302 on my 2006 Subaru sti. Just did a compression and leakdown. All within specs. Big relief. New to find the issue. Did all except injector swap

I have the otc kits. Already did a smoke test on intake and exhaust for the po302. 1st and last Subaru

I used to have one of those gadgets about 40yrs ago until someone "borrowed" it. Then I thought "how hard can it be to build one?" A small regulator, two pressure gauges and some form of small orifice between to upstream and downstream gauges. But that orifice size is pretty subjective - big hole will make the leak-down % small, and small hole make it a bigger leak-down number. Who gets to decide that? My latest thought was why not measure actual air flow (cfm) at a given inlet pressure? I just haven't built that yet, but still planning.

I just tore my engine down and got 91-95 on all cylinders besides #6 which came in at 82%. Had to be past the rings since it wasn’t coming out of the head but I didn’t see anything wrong taking it apart.

@TotalSeal

3 ай бұрын

Piston rock can also cause high leakage.

I checked my LQ9 build with gaped rings @.025 top .027 bottom and it was within 5% across the board after 15k miles checked a pentastar the same day 50-25% 😵‍💫

Those things typicly compare flow of the leak to the flow of a .040" hole it has inside. The same reading on a big engine is not the same as a smaller engine. 2% on a big engine is fine but the same 2% on a 125 motorcycle is a disaster. Testing at 100psi means you have trouble testing at anything but TDC. With lower pressure you can test down the bore. What is needed is a flow meter that shows the actual flow that can be related to cylinder size and get a true percentage.

I haven't used my Tavia leakdown tester for 30 years. I now have a high (294000) mileage Chevy S10. I'm scared to know what its going to read. 😁 First time I have seen a video about using one of these. Will i be able to tell from the hissing sound if the leaking is from the valves or rings? Im assuming so. ....heck, it will be both 😁 Great video.

@TotalSeal

3 ай бұрын

Thanks for sharing

Thanks for sharing lake.allways informative.its funny lake when you where young sent our time in Nascar pits.here in Australia I spent all my time in speedway pits.Steve Kinser was something special. I loved when Americans come out racing super sedans or as you say grand national throughout the 80s my brother was the racer.my brother brought a championship winning car from USA in 80 to 82.pay near 30 thousand for it back then.z28 carmaro with a 350 fuel injection stacks outa bonnet 3 speed with 3 gear levers quick change diff ect.car was fast won Australia championship. I love the smell of methanol i fell like I'm home.peace

@TotalSeal

3 ай бұрын

Thanks for sharing!

Lake keeps drilling down on fundamentals. He backtracks from the big engine to explain how it works in general.

@TotalSeal

3 ай бұрын

Thanks!

I have a weisco piston in a sb2 total seal ring 28 gap 4 thou wall clearance and it will leak 20 then i can just hold the crank enough to rock the piston and it leaks good. I really do not like it but weisco says its fine. Any thoughts

@TotalSeal

3 ай бұрын

That is a piston rock issue. The difference should be less when the engine is warmed up.

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.

Is it best to do a leakdown and compression test on a cold engine or hot cast iron block? What about aluminum?

@TotalSeal

3 ай бұрын

It can be done either way. Just know the results will be different hot to cold. The hot check numbers will be lower due to thermal expansion of the pistons and rings.

@gj91471

3 ай бұрын

Hot Engine

OMG, these guys seem to be fearful of grade 6 math...lol

You talk at length about not to worry about single digit differences but not anything about when you should start to worry. Also, is it more difficult to just divide to get the percent leakage or set it to 100 and have the crank spin on you out of control?

@TotalSeal

2 ай бұрын

The gauge has ranges that show when the results are outside of normal

Good stuff. This falls under the fundamentals, and should be emphasized, as too many fundamentals get neglected and dismissed, resulting in wasted time and money, for chasing own ass.

@TotalSeal

3 ай бұрын

Thanks!

Valves seats compression threw spark plugs magnetic valves seats magnetized helps seal

Hi Lake. Sorry guys. But you missed the mark here. You never mentioned if the tester you were using is properly calibrated or not and to what standard it is calibrated too? Without that information a leak down test is waist of time. Can you include those facts and the regulator type used in your next video please. Thank you. 🏁

@TotalSeal

3 ай бұрын

The Total Seal leak down testers are fully calibrated and are set up for 100 psi shop air.

Your left and right audio channels are reversed

@TotalSeal

3 ай бұрын

Thanks for letting us know

BlaBlaBla, you do a compression test first. if the compression is within specs, there's no need for a leak down test.

@fascistpedant758

3 ай бұрын

A compression test can be better if you know what compression that particular engine normally has at the condition you're doing the test at. A leak down test tells you precisely how much the leakage is and where it is leaking but it won't indicate valvetrain issues unless it's a valve being kept open.

@joe-hp4nk

3 ай бұрын

For a daily driven street engine, if the compression is 120psi or more and they're within 10% from the highest to the lowest, you're good.@@fascistpedant758