2001 Peugeot 306...1.9d non turbo.. 120,000 miles.. In Spain.. very good shape.. I just returned from a 700 mile roadtrip. After approximately 200 miles I was driving on the highway around 65mph and all of a sudden the tyipical "nuts and bolts in a coffee can" noise appeared and was impossible to miss, much louder than the normal idle noise.. I pulled off the highway and the noise went in time with the rev's.. I drove a few hundred meters to a service station and the noise persisted... I turned off the car and asked if a mechanic was there and was told he was a block away .. so i started the car.. and the noise had disappeared.. to my delight I threw caution to the wind and continued on the road another 500 miles there and back and I did hear the noise one morning on start up but just for two seconds..Since then all is normal.. .. any ideas?..