My old apache (1990 Mercedes 208D) Is having some terrible troubles with the heat here in Portugal. As it gets hotter there is a loud grinding/scraping horrible noise starts coming from somewhere on the drive train. Once it is cooled it runs smooth again. Anyone have any ideas what this might be. We spent hours sitting on the hard shoulders of motorways today as the engine got hotter and hotter climbing hills in the hot sunshine. It was a real struggle today! I have had to climb hills in 3rd gear at half revs as going up any faster or revving any higher has caused it to overheat and the noise is so scary!!!