986 duplex chain snapped - Page 1 - Boxster/Cayman - PistonHeads UK

Duplex chain that runs to sprocket on ims shaft has snapped at 67000 chain looks like it has snapped at ends of links as if excessive stretch Probable causes ??? Siezed ims ?? Or auto valve timing Adjuster ?? Valves bent on 2 cylinders on same bank

Taxi an said: Duplex chain that runs to sprocket on ims shaft has snapped at 67000 chain looks like it has snapped at ends of links as if excessive stretch Probable causes ??? Siezed ims ?? Or auto valve timing Adjuster ?? Valves bent on 2 cylinders on same bank Bummer. Causes? Well, the cliche comes to mind: A chain is only as strong as its weakest link. No sarcasm intended. It is just the cliche is true. Now it is possible the snapped chain was collateral damage from something else. A failed IMSB is I guess possible. Not seized as I've never heard of one seizing. But who knows? Doesn't make any difference. A tear down will be needed and possibly the true cause of the failure determined. Regardless the engine will be rebuilt provided the engine builder believes the engine is a good candidate for a rebuild.

Thanks for that. Obviously want to find the root cause not just replace broken bits just wondered if this was a common Porsche issue

Taxi an said: Thanks for that. Obviously want to find the root cause not just replace broken bits just wondered if this was a common Porsche issue My take is the chain snapping on its own and not as collateral damage is not a common failure. Sure, it happens, as you unfortunately know all too well. It is hard to know what happened exactly until the engine is opened up. Even then one might not be able to say with 100% confidence. Generally when a chain fails outright the cause is a material defect in the chain, probably in a link plate, but it could have been a pin too. Or less often is the chain develops a spot of corrosion and over time this develops into, pardon the expression, a weak link in the chain. (This can happen to valve springs, too, and the valve spring snaps from this corrosion.) While I can understand your desire to know, and anyone who experienced this would naturally want to know, if the engine is salvageable, the engine torn down, cleaned up, the broken bits replaced, and any other things taken care of that need taking care of, the odds are the engine will be fine for a long time afterwards. The chain just failed and not because of something else amiss in the engine. Barring infant death of the new chain -- which is why you want some warranty on parts/labor by anyone who rebuilds the engine -- it won't happen again.