recently had to change the water pump on my 98 ram van w/ a 3.9l. heat was awesome before i changed it. now the heat is barely there. changed the thermostat, flushed the heater core, but only feel light heat while the rpms r up. gauge on dash doesnt go as high as it used to either.is it possible that the new pump could be bad causing this?

 

I would suspect the thermostat first you might have gotten a defective one or its stuck open. You might also have gotten the wrong temperature thermostat which would keep the water from reaching proper temp. since you said the guage doesn't reach level reached before. I would change the thermostat first since its an easier repair than the waterpump. I would also check the inlet and outlet hoses to the heater core. If the inlet hose is hot and outlet hose it cold you might have a clogged heater core even though you flushed it out something might have gotten into it. Good luck and log back if you find the problem or need more help.

 

i checked and both hoses from the heater core are getting hot. i also checked the temp door and it seems to be closing all the way too. i will change the thermotsat again and see if that corrects it.thanks and i will keep u posted....

 

Probably have an air pocket in the heater core. (flush should have taken care of that though.....did you flush both directions?)