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I have a 90 f-350 7.3 and a 84 F-250 6.9. Did a full coolant flush on both and thanks to this forum was able to find both the passenger side and driver side drain plugs. Well the '84 had plenty of coolant come out of both plugs but the '90 had nothing come out of the passenger side. The driver side had plenty.
The '90 truck does run warmer than the '84 but never has overheated. The heater in the '90 doesn't produce any warm air but I figure I just need to do a flush of the heater core.
My question is, what does the passenger side drain plug actually drain and do I have a problem that nothing came out?
Don’t know the answer, but what happens if you put the driver’s side plug back in, leave the passenger side plug out, and pour water in the coolant tank?
pour a gallon of water in. If nothing comes out the passenger plug, open the driver’s side plug and see if the full gallon comes out
Not sure. I took out the passenger side plug out first and was surprised when nothing came out. Then went to the driver side and fluid came out of that one.
I'll have to try that after I do the heater core flush.
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