Sixth Gen VTEC cam chain tensioner theory of failure.

I have a 2003 VFR which has begun the unmistakeable Cam Chain Tensioner rattle.

It is right about on schedule, as the odo is showing around 40K.

I am fairly certain it is the front one and have bought a Honda replacement and am preparing to replace it. I have read most of the very good info here and a few other places concerning this endeavor.

I am simply uncertain how rerplacing a part as simple as the tensioner can cure the problem. As we all understand, there is a long foot, if you will, which pivots at one end and rides against the outside of the cam chain. Pressure is applied against this foot by the tensioner to remove working fluctuations in chain tension and, additionally, to continuously adjust the foot position to compensate for wear.

Looking at the tensioner, it appears to be a spring loaded screw assmbly acting as a rotary ratchet, rotating the tensioner out as wear progresses over time. This is a one-way operation, IE: the spring loaded screw will find it easy to rotate the plunger out, but there will never be enough pressure to cause the screw to rotate against the spring.

In conjunction with this, there is enging oil supplied under pressure which tends to force the tensioner plunger out against the foot, and it is held out at it's position by the spring/screw/ratchet assembly.

OK so far so good. So how does the tensioner fail? And more importantly, how does replacing it cure the problem? There are a few possible failure modes: The spring can break, or fatigue over time and stop acting as a ratchet, I assume. But reading on the issue never mentions broken springs.

The plunger could reach the end of it's travel, and as the replacement is identical, replacement would not cure the problem.

Or, the plunger could wear enough that there is too much oil leakage around it and it is no longer acting as an almost ideal piston and is not able to exert as much pressure on the foot as designed, hence opening the oil hole would probably cure it, without replacing the tensioner at all. This could explain the mysteriously small hole in the gasket for oil to begin with.



Incidentally, there is much written about disassembling the tensioner and adding more 'wind' to the spring, leading me to believe the oil situation above makes the most sense.