Pump coupler machining content

[true temper]

I have a diesel fired pressure washer, about once a year the burner quits heating. The plastic coupler between the fan and the diesel pump melts, and the diesel pump quits pumping.
I think what’s happening is I have it vented out of the north wall of my shop. When I turn it off and the wind is blowing out of the north it forces hot air down and melting the coupler. I had a new coupler on hand but it was too short so I built one out of aluminum.