well unplugging it didn't work, Not sure where to go from here. I don't think the core is plugged the car doesn't have very many miles on it and has always been serviced with new coolant and such. The old M valve did have a torn bellows so pretty sure that must be it. Is there any way to test it on the bench? I'm not even sure what it is supposed to do. Like I said I had to take the old one apart and put the new ones parts on it as the new one didn't fit very well. Maybe it is just crap to start with. When I had it apart the aux pump was working as I checked it and could see the coolant flowing in the valve. The hoses are not hot so safe to say no coolant getting in the core. If I squeeze them I have heat for a bit. Nothing is ever straight forward it seems.

__________________
1987 300 TDT
1990 300 SEL