Not sure if this applies to the type of common tensioner failures, but during the rebuild of my 2.7, one pressure-fed tensioner never came up to proper tension. In fact, I didn't notice this until I fired it up and got a faint rattling sound from the chain. The internal spring was holding up the tensioner (sort of), but with no/little oil pressure.
Upon inspection, oil was not getting into the chamber. I blasted some compressed air into the inlet port and heard a click. It was the sound of the check ball dislodging from whatever was keeping it from moving (bad casting/machining flashing?). Apparently this fixed it as the passage opened up. The tensioner has worked fine since (4+ yrs.).
The PF tensioner is basically a hunk of metal with a piston supported by oil pressure. The piston-to-wall clearance allows oil to slowly bleed out but not so fast as to collapse the piston (sort of like a hydraulic lifter). Are these failures caused by too large piston clearance or restricted inlet oil flow? Also, not sure how priming a new tensioner validates it'll work under pressure unless excessive piston clearance doesn't allow the piston to extend and provide adequate tension during the install.
Just my $.02
Sherwood Lee
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