[AlpineBimmer_E46]

Ok so the car has all nee coolant hoses, expansion tank, thermostat, temp sensor, and fan. The coolant hard lines, and heater valve are about 10 months old and the radiator is about 18 months old. Heater core was also flushed 10 months ago.
I went through and PROPERLY bled the coolant system numerous times. The last time i did it(last night) it seemed to help a lot!
However, i get warm air wen idling but its a furnace when driving. I have confirmed all the sensors and heater valve are working through INPA. Why dont i have heat???

 

[AlpineBimmer_E46]

This is pretty normal on most cars for a few reasons.

• The coolant is flowing more when you are driving
• Air is flowing through your hood when driving
• And probably another reason I can't remember.

It used to stay hot no matter if im driving or idle

 

[AlpineBimmer_E46]

Read post #13 on how to bleed the engine: overheating at idle

I have PROPERLY bled the system already. This is my 6th BMW. I’ve had this problem before but its usually the thermostat, heater valve, or the sensor behind the climate control panel… all these things are in working order

 

[AlpineBimmer_E46]

Turn the fan high and see if more air blowing.

I can adjust the fan speeds no problem… problem is when the car is idle, i get warm air, when the car is moving or rpm’s are above 1.5k i get HOT air…

 

[AlpineBimmer_E46]

OK, so the issue is not enough coolant flowing through the heater core at idle speed. Disconnect the heater valve connector and see if it changes.
Did you feel the rad lower hose and was it hot?

No change when i unplug the heater valve, lower rad hose gets hot.

 

[AlpineBimmer_E46]

I don't see water pump listed.

Was also replaced 10 months ago… problem was still here with old water pump

 

[AlpineBimmer_E46]

Did you change the water pump with all those hoses and other cooling parts? Maybe its a little weak and not moving the coolant enough untill the rpms are raised, and having a proper mix of coolant and water is important to, to much water in the mix might not retain the heat throughout the system as much.

Yea water pump was changed 10 months ago as well… had the problem before all these parts were changed

 

[AlpineBimmer_E46]

Then you are having a clogged up heater core or the heater hard pipe under the intake manifold.
Do this: remove the Tstat, disconnect the heater return hose that connected to the back of the tank, then back flush the hose with garden hose water. This should push the water through heater core, the heater valve, then through the head and out at Tstat opening.

So 10 months ago, i did a motor swap 2.5L to 3.0 and auto to manual conversion… i flushed the heater core really good because the car had this problem before the swap. Thats why a lot of parts were changed 10 months ago…

 

[AlpineBimmer_E46]

New 2 hard pipes, heater valve too?

Yes i did new hardlines, waterpump, heater valve and flushed the heater core when i did my motor swap 10 months ago. New e-fan, thermostat, coolant hoses, lower temp sensor, and expansion tank have all been done last week.

 

[AlpineBimmer_E46]

Could be the auto tranny cooler Tstat failed in open position dumping cold radiator coolant back to engine.

Car is 5spd