I've recently made an observation on the '87 SDL that I'd like to have confirmed by others.

Firstly, this vehicle has no a/c at the present time, so, naturally, I prefer to use the fan on high speed to move some outside air through the vehicle. This works perfectly fine on the first start of the day while the engine is cold and hasn't reached temperature.

However, on subsequent starts, the temperature of the discharge air is estimated to be at least 15F. above ambient on starting.........gradually getting closer to ambient as the vehicle is driven for a distance.........but never quite making ambient temps.

My thought is that the heater core is flooded with hot coolant upon shutdown because the monovalve opens fully.

Is anyone aware of a check valve that prevents this behavior? For those using a/c, it must overcome the hot coolant in the heater core, thereby making a marginal system that much worse.

Anyone with some input or willing to confirm the above is welcome to chime in.