Originally Posted by kerry

I don't think anyone ever argued that the garbage bag test was a substitute for a compression or leak down test. If my aging memory serves me correctly the garbage bag test was invented as a substitute which was being advocated on here about 8 years ago or so. It was to plug the PCV hose and count how many seconds before the engine shut down from the internal pressure pushing out the shut off diaphragm. People pointed out that that particular test could either blow out seals or be useless if seals had already failed.