So, long story short, I'm having issues with my 2000 Dodge Avenger ES V6 2.5L. It's overheating and the heater is not blowing hot air. Blower works on all speeds, AC works, all fans are turning on at their correct times, I replaced the thermostat (which opens at a cooler temp than the old one), got a coolant flush, checked for leaks on radiator and hoses (none). At this point, everyone is telling me it's the heater core or water pump. But two mechanics have said its not the water pump. I need you guys to pressure me towards the smarter option. Some videos I've watched show that the car doesn't overheat even if it's the heater core. So I'm at a loss currently please help

 

Heater core will not cause overheating.

Question one: How do the mechanics know it's not the water pump?
Question two: How does your coolant look?
Question three: How does your oil look?
Question four: Have you replaced the radiator cap?
Question five: Was the all the air relieved from the cooling system after the flush?

A bad water pump can cause both of your symptoms.
If there is oil in your coolant or coolant in your oil, you have a headgasket blown.
If your cap is not holding pressure you won't get proper coolant flow, which can cause overheating and lack of heat.
If there is air in the system it can also cause overheating and lack of heat.
2.5Ls are a nuisance to get all the air bubbles out, so if the shop doesn't know what they're doing you could just have air in the system.

 

Question one: How do the mechanics know it's not the water pump?

They believe they would see leaks or that there would be a slight grinding sound.

Question two: How does your coolant look?

Coolant was flushed and looks good, no oil in it, it didn't have any before either, the color always stayed the color of the antifreeze (green). The overflow reservoir overfills when the car overheats. Even more so more so because the car should be full on coolant.

Question three: How does your oil look?

Oil is also good, I just had an oil change that was unrelated. It was just that time and i figured why not while the coolant got flushed. But I check my oil regularly because of a worry of a leak ever appearing. It's an old car.

Question four: Have you replaced the radiator cap?

Yes I did. Old one was a bit weak and slighy bent from shooting off and slightly burning my hand. But that was the first thing i did.

Question five: Was the all the air relieved from the cooling system after the flush?

Yes, at least it should be, I'm inexperienced with the equipment but they use some sort of pressure pump to push the air and then coolant. Thing is the car oveheated during the first try on the flush. Which forced me to turn the car off and then the pressure being released out the radiator mouth. They waited, tryed again, then it worked.

Thank you for the help, I really appreciate it!

 

Their first mistake.
I've seen these water pumps with no other signs of issue, but once pulled discovered the fins missing.

 

I would have recommend to replace the water pump, Because if I can't see the coolant flowing at the radiator. Then I know the water pump fins are not spinning and causing the vehicle to overheat. A bad water pump could also cause a engine misfire too.

 

The water pump is driven off the back side of the timing belt.

A bad water pump CANNOT cause missfires directy, there are no timing marks or
sensors on it.

I had a 2000 ES, more than likely, it's the pump, the impeller blades broke off.