Have recently greased idler pully bearing and rotated the tensioner bushes and installed new belt. Have noticed in the last week that at 3700rpm a pingy rattle begins till about 3900rpm and then dissapears. It is exactly at this rpm every time. If I run it through the revs a few times it stops, but will be there again later. Any one had similar issue? I am wondering if its the tensioner gadget on the belt. When I had it off I lifted the boot and let a small amount of oil out. I put a similar amount of light engine oil back in (half a teaspoon). Must say I am not really sure how the hydraulic part of this little gadget works, wonder if the oil stops it from bouncing around, sort of like a shock absorber? Belt feels tight enough....cheers.