My research indicated that the 90's 5 cyl 2.5L diesel (602) engines do not have unusual head problem. The chance of getting a cracked head is no more than other engines with aluminum head. However, the early 603 (6 cyl) engine (no info on early 602 engine), as in 87 300D, has a problem with cracked head due to design. Sometimes, it just cracks, overheated or not. The replacement head should be better.