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Matt, Engineer
Category: BMW
Satisfied Customers: 21357
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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2004 x3 3.0 no/weak heat. Slight heat at high rpm (4000rpm

Customer Question

2004 x3 3.0 no/weak heat. Slight heat at high rpm (4000rpm and up). Replaced water pump, heater control valve, bleed coolant system, stil not fix. bought car this way with this problem.
Submitted: 6 months ago.
Category: BMW
Customer: replied 6 months ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Matt replied 6 months ago.


Very first thing to do is ensure the coolant level is up to the mark and if low top it up with the correct antifreeze or pre-mixed coolant as stated in the owners manual

I'd then check that the engine is getting up to temperature, if its not then its likely the thermostat needs changing.

If this is OK have a feel of the two coolant pipes that pass into the car through the engine bay bulkhead, both should be warm with a warm engine. If they're not then its likely the heater matrix is blocked and you should do a reverse flush on the cooling system to try and clean it out. This is done by removing the top hose from the radiator and placing a garden hose into the engine water outlet, and then run the hose until you get clean water coming out of the radiator.

If this doesn't help this only leaves checking out the motor / cable that moves the air mixing flap that allows the hot air from the matrix to enter the car air system.

This flap is controlled by the temperature knob / dial etc and I think is controlled with a small motor for your car so the thing to do is first get access to the back of the control knob and measure the voltages is present there, then trace the wiring back into the dash from the control to locate the motor.

It’s worth first checking the fuses for the fan / control circuit

I'd recommend first removing the glovebox ( undo lower edge hinges from dash) to gain access to the dashboard inner and also allow you to shine a torch to the back of the central console so you can start tracing the wire back and see how things are put together

Customer: replied 6 months ago.
thermostat, water pump, blower fan, is all good. I found that heater coolant control valve is always stuck shut upon ignition- so i removed the plug to it for it to stay open. I have changed the evap core temperature sensor and still no fixing. with cool;ant control valve open i get warm air circuation but not hot air in cabin unless i rev engine above 3000 rpm
Expert:  Matt replied 6 months ago.


there's a separate small electric pump to circulate the heater coolant

so check that its working and that its bled

this video shows how

Customer: replied 6 months ago.
my vehicle does NOT have that pump. I even got a new one and took to mechanic and they spent hour running all lines and no such coolant pump on the 3.0 x3 2004.
Customer: replied 6 months ago.
i have no problem with coolant circulatio now that the control valve is left unplugged- hot air blows okay, but issue is why would signal always stay on to keep valve closed- we replaced temp meter in fins behind dash vents 2x, still no solving.
Expert:  Matt replied 6 months ago.


I'm going ot have to opt out as I don't have this system information to help

best of luck

another expert will be along shortly