Idle rattle checklist

Hi -

Have trawled the archives but grateful for any thoughts! TD5 engine c.185k miles, has just developed a pretty harsh rattle, only really noticeable at idle (or v low speeds) - happens in gear or out.

I've seen a couple obvious things it could be, namely:

1) the crankshaft pulley damper

2) accessory belt tensioner

Haven't taken a video of mine but it sounds an awful lot like this one I found on Youtube:



or indeed this one!



I've not been able to ascertain exactly how I could differentiate between those two causes - and not seen any other obvious culprits... grateful for any thoughts from the knowledgable folk here though! I note the second video has a kind of extra 'clunk' after the engine shuts off which I haven't entirely confirmed but does sound familiar - is that a telltale sign of the crankshaft pulley?

[Sorry if I've missed the crucial thread that explains all this perfectly already!]

remove the belt then run engine does the engine noise still appear the rubber inside the harmonic balancer could be worn out resulting in the lugs of the balancer hitting metal against metal

you can also check the back lash on the belt depending how good the dampener is

but removing the belt and running engine can rule out all other pulleys

if it is the 3 lugs on the balancer hitting the sides I would get this fixes asap as the 3 lugs holding the balancer weight can snap off creating more damage.... or you can remove the weight via the 3 bolt on the lugs pulley stays on the crank shaft but this is only a band aid fix

if you purchase a one ask them is this genuine or after market ..the after market ones have a slightly different material the cast and may explode at any time ..trust me I have been down this road twice in the space of 9 months

Super useful, just what I was looking for, thanks ozzyboydeano!