Reply To: 59 Pressure Vessel
The “Pressure Vessel” is truly the Vacuum reserve tank. I have a few 59 Mercurys and have never encountered oil in a vacuum tank. The oil being red might indicate transmission oil, however 59 mercury should not have a vacuum diaphragm on the transmission. If the vehicle was equipped with the rare option of a “Multiluber” there could be a leaking diaphragm at that pump that possibly entered the system. Drain it out and drive it. A little oil down the intake is good for valve guides.