Yes you can but you have to remember that some leaks only show up when the engine is hot and cracks expand, and some only show up when the engine is cold. There is a tester called a "cylinder leakage tester" or "cylinder leak down tester" that does just what you're asking. You must put each cylinder, one at a time, at top dead center on the compression stroke, then compressed air is supplied to the tool, and air pressure regulated to around 30 psi is forced into the spark plug hole.
You look for the results of any leakage in four places. If you hear hissing at the throttle body or carburetor, you have a leaking intake valve. At the tail pipe; a leaking exhaust valve. Leakage past the rings will show up at the oil cap or dipstick tube. A cracked head or leaking head gasket will cause bubbles to show up in the radiator. With relatively small leaks, the air will sail right past the thermostat and be forced into the reservoir by normal cooling system pressure and you might not even know there's a problem. It's the larger leaks that can cause the thermostat to close.
Many thermostats have a small bleed hole to help hot coolant get from where it became hot to the thermostat where it will be sensed and cause the thermostat to open. During the leakage test, air from the combustion chamber sneaks through that bleed hole and goes to the radiator. For thermostats without that bleed hole, air must find another way, usually through the heater core, so it can take a while to show up where you can see the bubbles. You can watch to see if the coolant level is rising in the radiator, but the tester also has a gauge to show the percentage of leakage. Typically anything under 10 percent is acceptable. If you find much more than that in one cylinder but no other hissing is noticed, give that one plenty of time for the bubbles to show up. The air has to be going somewhere. Also listen at the spark plug holes for adjacent cylinders. A head gasket can leak between cylinders, but that isn't what your symptoms suggest.
Tuesday, April 24th, 2012 AT 8:07 PM