No Heat At Idle

[tacroteau]

Hello everyone, I just bought my first BMW a week ago and I love it! One problem though, its a 98 528I with a million (209,000) miles on it. Perfectly maintained w/records. The weather here is around 20 to 30 deg, and at idle the car will never warm up. Once driving she is fine, and the blower cycles up and down correctly as needed. As soon as I come to a stop at a light first the passanger side blows cold then the drivers side. The engine temp is a perfect 12 oclock, except for one time when it went into the red at idle (clearly the thermostat got stuck). Any ideas on this heat problem. This car is new to me and this HVAC system is quite complicated. Thanks,

Tom

[CiscoKid]

it pumps coolant throught the heater core, when you are idleing, the watepump is not pumping as much water

[tacroteau]

Yes, but should it actually blow cold? How are you suppost to warm up your car in the morning, if it wont warm up unless moving?

[rsn48]

Well if it were me, I'd have it in to the BMW service department and their computer readings would tell them right away. But the first suspect is the the thermostat, if its red lined once, clearly there is something wrong with it.

But I can give you my experience with this problem, and you might not like it. There are two other causes of this (other than a sensor needing replacing), one is the heater core has become clogged, which doesn't happen on most cars but it did on my dearly departed Mazda Protege. This will restricted air from warming up, so since you car does warm up it might not be that.

The other your rings, if you are going through lots of oil and smoking a bit, you could have "blow back" which will affect your heating system as well..

Good luck and I hope it something cheap for you.

[billB]

Start with a good thermostat then work your way up through more expensive stuff!!

[CiscoKid]

mine aslo stays cold at idle... until it is warmed up

[billB]

Assume a good working system; once your temp needle reaches the half mark, the system had built enough pressure/temp to give you heat in the cabin. In fact when idling, engines tend to get hotter thus rise in coolant temp (this explains why your auxiliary kicks in -sensor dependant- when idling in traffic jams) all in all = hot air in cabin.
But when the thermo is stuck “open” it will take you forever to heat the coolant because “closed” is the default position of the thermo when cold so think 2 things are happening:
A. Less coolant for engine to heat up at cold starts=faster heat in cabin=closed thermo=no coolant circulation; period.
B. This "closed position" aid in building enough pressure/temp to get the system up and running=open (temp dependant)=entire HOT coolant is set in motion; your heater core included. Again assuming good working HCV

Note: Bad Heater Control Valve will ruin a wedding on a nice Sunday afternoon
regards
Billb