The design of the heat exchanger filler necks and pressure caps used on Vetus Diesel engines was changed in 2019
The original filler caps, STM9507 and STM1017 are no longer available.
The original filler necks, STM3750 and STM1515 are also no longer available.
The new pressure cap is black plastic and the same one is used for heat-exchanger cooled engines and keel-cooled engines - regardless of whether they have a calorifier or expansion tank fitted.
The cap vents at 1.0 bar and a small length of pipe can be used to drain any coolant overflow into the bilge.
If you are replacing the original metal pressure cap with the new black plastic cap, you must also replace the filler neck at the same with the new type. Replacement of the filler neck is relatively simple: unscrew the original and screw in the new one, then tighten it.
Part references:
SETDOPM - filler neck & filler cap
18-14715 - filler cap only
18-14649 - filler neck only
