[mclendonka2]

OK, this has been a battle for the past 8 yrs. 2000 Dakota, 4dr, 3.9

No heat, Fan motor is fine, temp control works OK,; temp gauge on dash wont get above approx. 160(thermostat was replaced in 2014 to a 190, still didnt get warm, not even 50 on a cold morning. Blend door seems to be OK, AC is good when it works(thats another story). Had the truck to overheat this year when radiator cap wasnt put on properly(temp gauge did go up into 210 range(so i know it does work). Even in the summer the truck wont get to the 1/3 scale(beginning of semi circular line at mid scale of indicator scale)

Jan 2022....redirected heater core return line(used to go to water pump) to main radiator hose to radiator(didnt help), coolant is dirt brown in color, not green/yellow, and is at proper level. Even had airflow for radiator blocked off to help get heat level up(no luck). Temp gauge stuck into radiator fins didnt even register 135...?? and was able to immediately open the radiator cap.

What else can it be:

Would a bad(Open constantly) thermostat cause truck to not build heat that bad, even w airflow blocked.
(Will a 160 work better than 190, would stay closed longer to build heat?)

Clogged output on manifold TO heater core be blocked.

Would old antifreeze cause anything?

Is it true radiator in this model truck is over sized and is universal to even the biggest engine?

HAVENT back flushed core or radiator/engine

IS MY TRUCK POSESSED.........HELP

PHOTO...........Yellow line indicates HIGHEST positiion needle goes

 

[mclendonka2]

Update: Changed thermostat from 180 to 160, still no appreciable warm air. Temp gauge obviously doesnt go up as far. Good flow through top radiator hose, but heater return hose is much cooler than main hose. Temp of fluid read 172, w/ the 160 degree thermostat(measured directly in the fluid flowing by the filler neck. Only obvious issue is now back flushing heater core and getting some cleaning fluid through it. Then a complete flush and refill. Still not know why temp is so low even w cooling air blocked.

PHOTO.........Green line is 160 temp(new thermostat)......Yellow line is 180(previous thermostat)

 

[mclendonka2]

Last Update: Finally , I have heat

This was heading toward my last ditch effort of doing a radiator flush and was swapping the radiator hoses to be able to do a natural 'reverse flush'. Drove it to pick up my daughter and whala, heat.......... I sorta figured(crossing my fingers actually), that the reverse flow would dislodge any buildup on the inlet side of the core and flush is away. Now my temp gauge goes almost to 210 and I have enough heat to run me out of the cab.

Still plan on running a chemical flush treatment through and a partial dump and refill. Now, i plan on keeping a gallon of water AND antifreeze in the truck for unknown issues that arise.

 

[jerry57g]

I had the same kind of issue with a GMC 2500 I own. Backflushed the heater core and flushed out basically reddish mud. Since then heater works fine even in the -20 stuff.