The aluminum head on the 124.133 is carefully designed to have as close to perfect, a coefficient of expansion and contraction within the temperature range present. Mercedes is not alone in this quandry. Most of the better built cars out there have aluminum heads. A 1987 300d Turbo is almost eighteen years old! When I bought mine, and called MBUS tospeak with a technician, I was connected tothe head person. He explained that this was a special edition of the 124 series and that it was the first time that MB used a six cylinder turbo diesel in this size car. All previous engines were four or five cylinder. He told me that I could expect over 300k miles before major engine work. He owns the same car, and two of his techs plus his secretary also own the same car. It is very rare as it was only imported in
1987. Unlike other 124 body sedans, this model came standard with dual driver's memory and headlight wipers. The best replacement head for this car is the head from the 1986 300SD Turbodiesel (126 body). It brings with it more horsepower and it is a direct fit. All replacement heads are aluminum. P.