i have a 1998 dodge ram 1500 5.2L i've replayed the t-stat, rad, heater core on 1998 Dodge Ram 1500

and the water pump and the upper hose is hot and the lower hose is cold. it sounds like a flow problem but can not find or know where to start. still has heat but temp gauge not reading right.

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2 answers
Your heater core is plugged.
Reverse flush it with water and air.
I have done mine a few times now.
I get pieces of gasket looking material out every time.
Works great for about a year and then I do it all over again.
Take out your t-stat to verify that you don't have plugged up water jackets in your engine. The coolant should really flow. I have also seen an after market t-stat not flow properly, so be sure of that. If the coolant flows and both hoses get warm-hot, then you may have gotten a defective thermostat.