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Soo, With European studded Snow tyres on, and the wonky power steering now fixed. This is an AMAZING ride in the Winter. Every bit as fun as the old Audi Quattro I used to have years ago, just with a LOT more Cowbell

Except... Cabin Heat.
It is not cutting it. Apparently when it works it is supposedly very efficient, not so much on this truck though.
So far I have flushed the heater and backflushed the QD on the intake going to the heater, including the hoses to and from the heater. There were no signs of blockage anywhere really and the water coming out of the heater was clean.
What I have noticed so far is engine temp is not stable and fluctuating between maye 60-90 degrees centigrade. But it is difficult to say really becase the scale on the gauge is a bit weird. I'm going to start with replacing the Thermostat with a 195F from Gates.
Also, the hose going into the heater is only hot...ish I can hold it but I'm not sure my wife could

. The same hose on the 2008 Suburban is somewhat hotter, hot enough that I can't hold it very long.
The hose coming out of the heater in the truck is maybe luke warm, on the Burb it is significantly hotter.
The blend door actuator seems to be working fine and the fact that the heater return water is not hot points to a flow problem and not an actuator issue.
I've topped up the coolant and tried to bleed the system with the truck at an incline to rule out air pockets which did not change anything.
So what should be my next move? Maybe the new thermostat will fix everything? (I doubt it will but I think it is part of the problem at least)
Is a clapped out water pump a likely cause on these engines? (1990 350TBI) It does not leak or show any other signs of mechanical distress though.