Confusing Heater Issue

I feel like i've been asking way too many questions lately, but this is my first Bimmer, so i guess i'm just getting used to it... and i don't wanna pay dealer costs to diagnose unless i have to....

Its getting pretty cold here in PA... When i go out in the morning and start the car, the heater blows fine regardless of what setting its on (Auto or Vent)... heat blows nicely to both sides of the car.... Then, once the cab is warmed up, for some reason the passenger side of the cab starts to blow cold, no matter how high I turn it up - even to the max of 84*.... I checked the rear vents, and the same thing is happening - on the driver's side rear, it continues to blow hot air, but the passenger side rear begins blowing cold....

It doesn't matter what temperature i put it on, nor does it matter whether its Vent or Auto... Also, I HAVE gone into the settings in iDrive and changed the red/blue to all red, so that shouldn't be the problem...

As a final note, all the vents blow cold, even the ones to the floor

Cliff notes: heater is great until the cab is warmed up, then the passenger side of the car (front and rear) start blowing cold, while the driver's side (front and rear) blow hot as they should....

Any ideas/help?

Edit: forgot to mention - its a 2007 X5 4.8i

i would normally guess that its some sort of blend-door issue, but since it blows nice and hot at first, i'm at a loss..... researched the entire inter-web via Google and can't find anyone that has had the same issue

Hi,

Did you ever get to solve your problem as I am having the same exact issue and I am puzzled as well, checked and replaced sensors but no use.

Hope you can post your solution soon!

Thanks,

Originally Posted by hilander

Hi,

Did you ever get to solve your problem as I am having the same exact issue and I am puzzled as well, checked and replaced sensors but no use.

Hope you can post your solution soon!

Thanks,

No, i have not figured it out.... I have been really busy lately, and since its more of an annoyance than a concern, i just haven't gotten to it....

If you figure anything out, please let me know... Eventually I'll probably take it to the dealer and see what they tell me...

Add me to the list with the same mysterious issue. 2010 35d. Anyone else experienced it? Or found an answer?

Here's what works for me.

First take it off "auto."

Then press either of the switches at the end of the panel. With each touch you direct air to windshield, torso or feet, or some combination, for, respectively, the driver or front seat passenger. The switches are independent of each other so adjustment can be individualized.

Then, for temp adjustment, go to the iDrive control dial and turn the dial. Watch what it does on the screen relative to temp. Adjust each side as needed.

This works much better than "auto," which we never use anymore. Simple, linear, immediate, intuitive. Bypass the auto setting, which is slow and frustrating; which you knew.

OK so here is the thing, I was following up with the service manager @ BMW and I described the issue to him, but the thing is before this issue happening to my car I replaced the water pump myself and what it seems is that I was having an air pocket somewhere in the cooling system, most likely the heating radiator which is located inside the car under the dash, so the second thing which happened was that the expansion tank got blown and of course I replaced that afterwards I noticed the heater problem.
After I dropped in an email to the service manager he just replied back that this seems to be an air pocket.................. so I knew I needed to bleed the air out of the system but the problem is that I couldn't find any post on how to do it for my car as there isn't and bleeding screw on the 4.8 engine and all the other posts tells you about the 3.0 which are having the water pump as electrical.
now what I am doing is every time I drive the car around and before I shut it off I open the cap for the expansion tank to relief the pressure of the air pocket and every time there is some air out... how ever today a lot of air came out........ so fingers crossed tomorrow will be another day with the hope that the heater will work just fine.
one more thing if this doesn't work I am planning to remove the temp sensor which is located on the temperature valve and let it bleed from there as most likely that is where the air pocket is located.
This has been long..... I know, but I think more information might help identify the issue.
one question though........ did every one with the same problem replaced a water pump or for any reason his coolant was drained flushed and refilled, cuz this would be the common thing and this is what we should be looking at.

Best of luck and please who ever finds the solution first post it up ASAP to help the others.

E70
2007
4.8
188K KM

OK so here is the update, today I decided that I want get it done with so I opened my whole system and traced the issue, basically if you have a humming sound that is hear able when you start the car until it warms up and this sound goes away when you switch off the blower, you need to check / replace the heater valve http://realoem.com/bmw/showparts.do?...91&hg=64&fg=18 item number 4 in the link.

it has two solenoids that are controlled by the control unit inside the car, I removed mine and opened it and found that the internal rubber is broken and in the way of the valve, so I removed the broken rubber and I tested both solenoids via ohm meter, one was 30.5 the other was 16.5 so I guess the one that was stuck is not fully functional any more thought it might work for now but will not be accurate, any how I rapped things up and assembled the unit and made sure this time that I flushed the heater radiator before I assembled every thing......... steps to follow while filling the coolant:

1- add coolant slowly into expansion tank
2- once coolant is visible and there is no sound of it going any where, insert the key and push start with out stepping on the brake(you don't want the engine to start at this point)
3- this will start the Additional water pump item number 1 in the same above link.
4- give it 5 to 10 min to fill out your heater radiator.
5- start the car and make sure to keep an eye on the coolant level as once the thermostat open the coolant level should drop.
6- I kept my car running about and hour with the cap of the expansion tank open to allow any air in the system out.

Bingo my heater is working, will keep an eye on it and will update tomorrow morning what behavior it exhibits when its colder.

hope this help others especially people that hear a strange sound coming near the expansion tank, this could be either the solenoid vibrating or the additional water pump, you might want to check both.

good luck to all.