My 2000MY Range rover 4.0 suffered a plug lead failure due to corrosion between the lead and the plug itself which caused arcing to the engine block. As the plugs do not need to be changed on a regular basis this is a common fault according to my dealer (in other words, it is not a service requirement to check them) .The car is 3.5 years old and covered only 30k miles. I have a 14 year old BMW which is still using original leads. What is the difference? Perhaps just better quality original equipment?
As the dealer simply recommends a full new set of leads, I inspected the remaining 7 plug/plug lead connections I found 5 to be in 'as new' condition and two to be corroded and in need of cleaning or perhaps replacement. The plug tops clean up OK, but the lead ends are more difficult. Should these be replaced? Why are some corroded and others not?