There is no chance 1987 505 engine will work efficiently with bad cooling. For filling up the system you will use 9.5 liters of special Green coolant type. It’s better to choose fluid in combination of 1986 year, 2.2 volume of motor and engine code of 851(ZDJ). It’s important to provide cooling for Peugeot’s engine with 2.5 liters volume. For sufficient use of Peugeot 505 you need to use suitable antifreeze.
Use your 2.5 engine longer in 1989 505 by keeping these rules. It will be advantageous to follow Peugeot’s rules for 1990 505 service. Every Peugeot owner should remember that engines with code 851(ZDJ) are quite demanding. If you choose other than Green coolant or use less than 8.4 liters, you can’t expect normal work.