Leak down test requires a leak down gizmo and a compressor. Basically you get a leak down tester, which has 2 pressure gauges on it and one end hooks to your compressor, and the other end to a hose with a fitting to screw into the spark plug hole. It fills your cylinder with compressed air and then measures how fast it leaks out of the cylinder. No cylinder rings seal perfectly, so it will give you a percentage reading on one of the gauges - mine has green, yellow and red zones to let you know if the rate is ok, or potential trouble. If the cylinder is not passing the test, it usually indicates the air is leaking past your rings - which indicates opportunity for
oil to get past them and into the combustion chamber. If you have a leaky gasket, or leaky valves, you might hear air escaping from the carb, or see bubbles in your water tank. You can find leak down testers for sale at Summit, or most parts stores will have them. If you have a friendly mechanic, they could do it as well. You'll have to decide which is more cost efficient - testers are maybe in the $100 range.
One other sign that pressure is going by the rings is that you'll likely get more blow by out of your breathers, or even out the dip stick, so check as see if the engine is oily in those areas too.
You can probably check a lot of symptoms before having to leap to the leak down test. Outside the blue smoke, spark plugs should be the initial indicator that you've got
oil in the combustion chamber. Then you have to figure out how it's getting there.
Also, keep track of your
oil level to see if it's losing any significant amount and just look around the block and under the car for any puddles.
You can do a web search on leak down test and find all sorts of articles explaining a lot more than I've said here.
Good luck!
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