Heater blows cold

[kahrlos]

I know there has been a lot of discussion on this topic, but can't find answer with search.

2003 530i just blows cold air even with heat set to 90 degrees. Temp guage at 12 o'clock. Does not overheat. Automatic Temp Controls, so has three hoses on firewall. Hoses cold on both sides of heater valve. System has been bled just too be sure. This car has the black expansion tank with 2 hoses. 1 of the hoses runs to what I beleve is the secondary water pump. With car at operating temp, this hose is cold, however, the hose on the other side of this unit which is at the bottom left of the radiator is hot. Is this the 2nd pump? I can hear water moving with iginition on and heater at 90 degrees with fan at lowest setting, and coolant comes out of the bleed screws as well. What is this thing, and if it's the 2nd pump, could it still be bad and not allowing the heater core to get hot?

[JimLev]

See the electric motor below the #6 solenoids
This electric motor should be running when the heat is on, it pumps hot coolant into the cabin core. It's mounted on the drivers side (US) strut tower.
It's possible that the MID that controls the #6 solenoids is bad and keeping the valves closed. To check that, unplug the connector to the valves, this will make them open. If the electric motor below is running you should get heat. Us V8 guys don't have that second pump at the bottom of the radiator, if it is running and the other pump on the strut tower is working you should get heat.
Report back what you find out.

[kahrlos]

Forgot to mention that I unplugged the connector to the valves as well. No heat. I do not remember hearing the motor under the valves and did not feel it for vibration. Will check that and report back....

[JimLev]

You will be able to feel it run if there is too much engine noise.

[JL]

Maybe I missed something but I'd assume final stage unit / blower motor resistor:

http://cgi.ebay.com/BMW-E46-E39-X5-X3-Blower-Motor-Resistor-Final-Stage_W0QQitemZ350198018076QQcmdZViewItemQQptZMoto rs_Car_Truck_Parts_Accessories?hash=item51896db01c

[kahrlos]

I can not locate any electric motor on the strut tower below #6. Only thing humming is #2, the additional water pump I originally mentioned. It is what gets hot on one side but not the other. Might be time to take hoses apart and run water through the core and valves. Any other ideas?

[JimLev]

What is the last 7 digits of your VIN? I can then look up your car's info.

[kahrlos]

[JimLev]

http://www.realoem.com/bmw/showparts...31&hg=64&fg=18

Pump #15, if like the others used in E34 and (I think E39's) have the motor magnetically coupled to the pump vanes. The motor could be running but the vanes of the pump not moving. That's the only thing I can think of. The top of the pump should come off if you want to inspect it.

[kahrlos]

Hard to believe additional water pump is not moving water when I can hear it and it comes out bleed holes when heat on with ignition in on pos. Thanks for the tips. Time to start taking stuff apart....

[nagib]

Carlos,

I have the exact same problem. Was wondering what ended up being the issue?

[arucano]

At the risk of being wrong, I thought the motor was only on when you have on the "rest" / latent heating after you turn off the engine. Normally the water to the heater is circulated by the main engine water pump. I would suspect the solonoid or the supply to the solonoid (#6)

good luckChet
'03 530I/S
Blk/Blk
The drive is the destination