If you have a compressor, the compression tester O'Reilly Auto Parts loans out can be used to make a poor man's leakdown tester. Just take the gauge off and Schrader valve out of the compression tester - it's the same size as a car valve stem Shrader - and adapt the hose to your compressor. For each cylinder, set at TDC and pressurize to 100psi or so. Bubbles will come out of the radiator for any leaking cylinder.

 

I'm just gonna take it to a shop for them to diagnose and do a compression test. I don't trust myself enough to do a leak test.