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2001 BMW 325xi A/T
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31 Posts
Discussion Starter · #1 ·
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???
 

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'02 330i 5MT
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1,277 Posts
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.
 

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2001 325 manual trans
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65 Posts
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.
 

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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…
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?
 

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2001 BMW 325xi A/T
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31 Posts
Discussion Starter · #14 ·
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
 

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No change when i unplug the heater valve, lower rad hose gets hot.
Yea water pump was changed 10 months ago as well
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.
 

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2001 325 manual trans
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65 Posts
I agree with Sapote, a plugged, or "sluggish" heater core might be it. You should be able to flush it with a garden hose and attachments.. Or you can reference my youtube video where I physically remove the heater core and replace the 2 o rings that seal it to the metal pipes. When I actually had it out of the car I flushed it with a garden hose.. not with crazy pressure or anything, just sealing a garden hose between my hand and the inlet of the core, 2 years later no problems and my cooling / hvac system basically functions like new.

 

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2001 BMW 325xi A/T
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31 Posts
Discussion Starter · #17 ·
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…
 

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2002 330i auto
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279 Posts
Have you replaced the heater valve, not much left at this point. I seem to remember swapping to a used spare or cleaning/freeing the valve when I flushed the core, but can't seem to remember exactly what I did. Either the spare valve or the one in the car was sticking.
 
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