No heat

I have a 2008 Tacoma v 6 auto with 63 k on it , I live in nj and this truck just came from Hawaii , the issue i have is there is no heat at idle , when you drive it gets heat . As of this posting the following things have been tried

1 The heater core has been replaced.

2 The t stat has been replaced .

3 The cooling system was eveacuated with a vacume coolant machine to rule out the system being air bound

When its running at idle at operating temperature the upper heater core hose is nice and hot but the lower return hose is bearly warm , rev the engine and they bith get hot . Any suggetions ? thanks Jim

 

My money is on something to do with the door that directs airflow to your feet. Does cold air work nice and strong?

 

No mods? Just in case. If you had underdrive pulleys that would cause it. But not likely you do.

Since it works off idle I am thinking water pump not putting out at low speeds.

Did you drive the truck in Hawaii? Or just since it's been in NJ? I imagine it's probably cold there right now and any overheating issue that it might have at idle is masked by the cold weather.

It's normal for the upper hose to be hot in comparison to the lower. That means heat is being removed as the coolant flows through the radiator. That's normal and desirable.

 

Ok , i did not drive it in Hawaii , it was shipped back here a a few weeks ago . There seems to be ample circulation in the rad even at idle and no overheating . We had a 50 deg. day last week and the temp stayed normal . Im gonna rule out an internal door issue , i think the tech that did the heater core would have noticed if the door was damaged when the core was replaced . But all that work was done before i got the truck . Im wondering if the control motor for the hot air door is not closeing all the way ( btw it switches to full cold with no issues ) . Thanks for the help guys , much appreciated

 

I just picked up an 08 Dbl Cab TRD Sport with 85k and just noticed that the heat isn' t working at idle either. I have only had it 3 days so the dealer is supposed to look at it tomorrow and take care if it. Since I have made the appointment the check engine light has come on with the Cylinder 4 misfire code. Little do they know they will be looking at that also. Ughhhhh

 

I know you mentioned you have replaced parts, but is the coolant low right now, or is it at the correct level?

 

It was the Head Gasket. I was told it was leaking exhaust back into the system causing a air pocket to find its way to the heater core and ultimately causing the no heat at idle and the cylinder 4 misfire reading. I am not a mechanic by any streach of the imagination but if this sounds right they found it by somehow an exhaust pressure test. The normal pressure test didn't show the leak. $2600 to fix by the dealer that sold me the used truck. They are taking care of it. Thank God!