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Am needing to do a leak down test and was wondering what type of set ups do y'all use?

They make actual leakdown testers for that purpose. I think I saw one a harbor freight for like 29.99 a couple of years ago. Some others that I have seen go for about 70.

Just what do you mean by a leak down test? You can do a test by putting compressed air in the cylinder to check how much air leaks by the rings and valves. Why do you want such a test. If that is what you are talking about, as for myself I have a fitting that fits in the spark plug hole with a hose on it an a quick disconnect that gos on my air hose. Do the test on TDC and hold the flywheel. Or are you talking about a coolant leak and want find the leak? Maybe a tire is leaking air? Need a little more information??

ILENGINE said:

They make actual leakdown testers for that purpose. I think I saw one a harbor freight for like 29.99 a couple of years ago. Some others that I have seen go for about 70.

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OK you seem to know, what is a leak down test?

A cylinder leak down test.
The shop I used to work at used a pressure/ vacuum pump because some gaskets may allow air to escape while in other situations an engine will suck air. I personally don't have anything to test this at my house and was just curious about different setups. Most use a mighty vac but parts stores just have the vacuum pump for bleeding brakes. I don't have a harbor freight in my town but will look online.

reynoldston said:

Just what do you mean by a leak down test? You can do a test by putting compressed air in the cylinder to check how much air leaks by the rings and valves. Why do you want such a test. If that is what you are talking about, as for myself I have a fitting that fits in the spark plug hole with a hose on it an a quick disconnect that gos on my air hose. Do the test on TDC and hold the flywheel. Or are you talking about a coolant leak and want find the leak? Maybe a tire is leaking air? Need a little more information??

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Reynoldston... What type of fitting is it you have. That is the same thing I was thinking about but that was how we done it on a 4 stroke. We just used the handheld pressure vac pump on 2 stroke. But I still need to find that fitting.

bwestbrook said:

Reynoldston... What type of fitting is it you have. That is the same thing I was thinking about but that was how we done it on a 4 stroke. We just used the handheld pressure vac pump on 2 stroke. But I still need to find that fitting.

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Mine is part of a Snap-on compression gauge. Just replaced the one way valve with a air hose fitting. You could maybe make something from a old spark plug? I guess I don't understand this test. Where are you putting the vacuum? In the cylinder chamber? Now once you have vacuum there what does it tell you as to what air pressure wouldn't tell you. You are going to have some vacuum leak by pass your rings? I am sorry I just never hear of this before and want to learn more. Is this something that you test on a 2 cycle engine? I know you need crankcase pressure on a 2 stroke engine and then this test would make more sense to me then?? Back when I was a car mechanic we would pressurize a cylinder to check for bad head gaskets, valves, or rings. To under stand more what are you working on?

It is to test the crankcase and cylinder to make sure there are no cracks causing it to suck air allowing it to run lean and it also checks the gasket or sealant to make sure there are no leaks.
Yes you would apply vacuum through the spark plug hole. The mighty vac pressure/vac pump allows you to check both without disconnecting anything.

bwestbrook said:

It is to test the crankcase and cylinder to make sure there are no cracks causing it to suck air allowing it to run lean and it also checks the gasket or sealant to make sure there are no leaks.
Yes you would apply vacuum through the spark plug hole. The mighty vac pressure/vac pump allows you to check both without disconnecting anything.

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Back to the same question what type of engine are you talking about 2 or 4 stroke? Where would you suck air to run lean other then the intake? What other leaks? Does the engine have to hold vacuum? If so how? Just trying to understand this test.

If working on a 2 cycle you block off the exhaust behind the muffler, block off the intake behind the carb. Use a mityvac to check pressure and vacuum of crankcase, never exceed 7 pounds of pressure or vacuum. Crankcase if sealed should hold pressure and vacuum.

You can have leaks around the sparkplug, intake manifold, crankcase gasket, crankshaft seals. If 2 cycle won't hold vacuum then pressurize crankcase and submerge crankcase in some liquid like parts solvent and look for bubbles.

4 cycle there is a special gauge to determine how much is leaking in percent of loss compared to input pressure.

ILENGINE said:

If working on a 2 cycle you block off the exhaust behind the muffler, block off the intake behind the carb. Use a mityvac to check pressure and vacuum of crankcase, never exceed 7 pounds of pressure or vacuum. Crankcase if sealed should hold pressure and vacuum.

You can have leaks around the sparkplug, intake manifold, crankcase gasket, crankshaft seals. If 2 cycle won't hold vacuum then pressurize crankcase and submerge crankcase in some liquid like parts solvent and look for bubbles.

4 cycle there is a special gauge to determine how much is leaking in percent of loss compared to input pressure.

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ILENGINE.... Exactly you explained it much better than I was. Thanks. It is a 2 cycle I am working on.

Thanks now when I see leak down test I will know what they are talking about. This would of been a good test back in my old snowmobile days when I worked on two cycle engines. I now understand what you are talking about. Like I said earlier I know that the crankcase is pressurized for a two cycle engine to run right. Really not much of a 4 cycle engine test and something I never did. It sounds like you would have to make something to block off the intake and exhaust manifolds and any vacuum ports. Also you would need a vacuum pump with a gauge. Just never ran across anything like that but will keep my eyes for it now. This is the second time I have seen it on this forum and the first time I never found out what they were talking about. Another thing I have always heard it called cycle not stroke, I guess just where I live and my way of saying it.

You can just take a piece of rubber like a tube for a tire a mount the carb and exhaust back on to block it off.