1962 Lincoln Town Car

If the bubbles in the radiator are from a leaking head gasket, you can usually determine which cylinder or cylinders are leaking by inspecting the spark plugs. On that old engine, the plugs in cylinders not leaking will likely have a dry, sooty appearance while those in the leaking cylinders may appear cleaner or wet, as if steam-cleaned (literally).

You can also tell which cylinders are leaking by presurizing the cylinders with air, one at a time.

For each cylinder

1. Remove the spark plug and install a compression gauge adapter (or other hose adapter that will screw into the spark plug hole) in the the cylinder being tested.

2. Turn the engine so both valves for the cylinder you want to test are closed and then hold the crankshaft in that position with a tool or fixture so it can't turn when the cylinder is pressurized.

3. Apply compressed air at 100-150PSI and observe for bubbles to appear in the radiator.

If bubbles appear when a cylinder is pressurized, then the head gasket is leaking around that cylinder.