The timing chain is one of the most crucial components inside a BMW or MINI engine as failure of the chain or other parts related to it such as the guides for the chain tensioner can lead to serious engine damage meaning a very expensive repair or replacement. Timing chain problems can manifest themselves in several ways including excessive noise, poor running of the engine and an engine warning light for example
This customer was experiencing poor running so wisely decided to have the problem investigated straight away. Initial diagnosis found that the camshaft to crankshaft position was outside of specification so upon removal of the cam cover the slack chain in the picture above was found.
After removal of the timing chain and its guide the problem was obvious and once drained of all its oil all this debris was found after removing the engines sump pan.
We also found that the oil pump had sucked up some of the debris from the broken guides thus restricting the flow of oil to the pump in turn reducing oil pressure so we decided to inspect the con rod bearings which are one of the first components to suffer due to oil starvation.
As you can see the lack of sufficient lubrication lead to the top coating of the bearing surface wearing though to the copper alloy material and once through to that material, wear is accelerated to point where it can damage the crankshaft meaning a much more expensive repair.
Caught just in time, a new set of bearings, new chain, chain guides and chain tensioner all timed up with the correct tooling meant this N43B20 engine was saved and the wise decision by the customer to have the fault investigated straight away saved them thousand of pounds.
Timing chain and guide failure is not an uncommon problem but one often not investigated thoroughly enough with other garages often only replacing the chain and guides without inspecting for further consequential problems.