What is causing a rattling noise to come from the inlet manifold of our Rover 75?

My wife and I have a much-loved 2004 Rover 75 V6 auto. We have had the car from new and it has 135,000 miles on the clock. It still runs beautifully and has just completed a 3,600-mile European tour. For the last 18 months it has developed a dreadful rattle from the inlet manifold and the garage say the cure means a complete new inlet manifold and has quoted between £600 and £700 for the repair. They also said the noise is a nuisance but not life threatening for the engine, so just carry on. We are reluctant to spend that much money on an elderly and high mileage car and doing nothing is an attractive option. Your opinion would be most welcome.

Asked on 21 January 2012 by PG, Woodley, Berks

Answered by Honest John
If these are inlet manifold swirl flaps rattling then, if one of then breaks off and gets ingested by the engine it could be fatal for the engine. Some people simply have the swirl flaps removed. The engine will be less efficient, but it's the cheapest way to solve the problem.
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