Monovalve Question
 

Car is a 1984 300 SD.

I'm replacing the entire monovalve housing. When I remove the tubes I suppose I will loose some coolant. How much?

Also, by replacing the entire unit am I going to introduce air into the system and if so how can I prevent it from happening?

Thanks.

Not much coolant loss, it sits high up in the cooling system. Don't worry about air in the system, it will readily bleed itself in a short test drive.