To accurately perform a cylinder leak down test, your engine needs to be at operating temperature.
Here’s how to perform the test using a ToolPRO Cylinder Leak Down Tester.
Step 1 - Careful Removal
Warm the engine up, then shut it down and dismantle everything necessary to gain access to the spark plugs. The oil dipstick, radiator cap, air intake hose, and positive crankcase ventilation valve also need to be removed.
Be certain to label each lead or coil with the cylinder they came off, and use compressed air to clear any debris before removing the spark plugs from each cylinder.
Step 2 - Measure Cylinders
For an accurate test, each cylinder being measured needs to be at top dead centre. A workshop manual will likely tell you how to set top dead centre on the first cylinder, but not for the remaining cylinders.
A crude way to determine this is to figure out where the compression stroke is - place a long screwdriver down the spark plug hole - and turn the engine over slowly by hand until the screwdriver just begins to lower.
Step 3 - Thread Adapter
Now, thread the adaptor hose and suitable fitting into the spark plug position. Connect a workshop air compressor to the regulator on the leak down tester, and ensure that the regulator on your compressor is set to no more than 100 PSI.
Before attaching the leak down tester to the cylinder, turn the inbuilt regulator until the needle on the percentage gauge reaches zero.
Step 4 - Test, Test, TEST!
When the gauge is attached to the cylinder, you will obtain a reading in percentage. The acceptable value is determined differently for each engine, but if the value is 20 percent or even worse, there may be significant wear or damage in the engine. Listen out for where the air might be escaping.
If it can be heard or felt rushing out of the dipstick hole or positive crankcase ventilation hose – it is most likely piston rings. If bubbles are seen in the coolant, there could be damage to the block or head gasket. And the sound of air hissing from within the inlet or exhaust manifold indicates burned, stuck or damaged valves.
Continue the test in the same manner across all cylinders if necessary, and write down each value for later comparison.
Rather than messing around trying to fix what you THINK is the problem, performing a test with the ToolPRO cylinder leak down tester will ensure you know exactly what needs repairing.
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