Morning guys,

What a great site! Just joined but wonder if any members can help me...my 1998 840Ci Sport's heater blows cold air out constantl, even when the climate control knobs are set to maximum heat. On occasions when I floor the accelerator (i.e. on a motorway, etc), and gather a decent level of speed, the heater sometimes springs into life and blows out hot air. In town at low speeds, I just get cold air coming out. Is this a common fault? Is there a simple fix?

Thanks for any help in advance.

Heater control valve and/or auxillary pump. Somewwhat common problem.

Heater control valve and/or auxillary pump. Somewwhat common problem.

Exactly............sticking heater solenoids/valves or the aux pump.........

You obviously havent seen my post from just before xmas!! Exactly the same problem. Turned out to be aux heating pump (was initially leaking ) it went in spectacular fashion at speed - but prior to doing so i had heating characteristics exactly as you describe. before you do anything though - check the coolant level in the radiator (resevoir) top up - not forgetting to bleed it correctly as well!! just as a basic starting point. Having replaced said pump all working exactly as it should now ..... good luck! florio

OK... I noticed the same problem on my 97 recently. Not that I take it out in the cold. Would one of you guys that are knowledgeable on the climate control sytem please provide some additional information?. Such as how to determine... and location? Heater solenoids... yikes! The aux pump I dealt with on my 5 and it was a piece of cake, are they similiar?
Yo thanks,
Rod

Just a thinking here....but is your little knob, located at the bottom of your center vents, turned to the 'red' dot?
Hope this helps,
P. Ford

The aux pump I dealt with on my 5 and it was a piece of cake, are they similiar?
Yo thanks,
Rod

Should be. I just replaced on on a friends 850 in 42 minutes from hood open to hood closed. Yes! my teacher was timing me.:):)

You obviously havent seen my post from just before xmas!! Exactly the same problem. Turned out to be aux heating pump (was initially leaking ) it went in spectacular fashion at speed - but prior to doing so i had heating characteristics exactly as you describe. before you do anything though - check the coolant level in the radiator (resevoir) top up - not forgetting to bleed it correctly as well!! just as a basic starting point. Having replaced said pump all working exactly as it should now ..... good luck! florio


Hi Florio,

Sorry! Just seen your last post (I'm new on here so bear with me!). Sounds like we both have the same problem with our 840s....must be the British weather causing these annoying problems. Can I ask, was the repair quite pricey for your aux heating pump and labour, etc? I am now petrified of mine blowing up like yours did on the motorway. I drive from London to Liverpool every weekend and I'm not very worried! I will check the coolant level tomorrow but fear that it may be the pump like yours was.

Hello again - yes well initially I noticed poor heating - apart from driving at speed as per your description, on inspection of my drive - I now believe that it may have been leaking for a week or so, but as you are aware wet winter weather is good at disguising such - however no low coolant warning. Posted questions on here and got similar responses as you have!! in the mean time continued driving - having checked coolant level assuming I would be ok until I could book her in (aside from a very cold cabin!) but as you may have read - the aux pump blew out on the M25 very spectacularly!! and fearing engine damage I obviously pulled over very rapidly and was trailered back to my trusted mechanics.
I obviously pointed them in the direction of the Aux pump (AA were convinced it was head gasket - wrong!) and was subsequently removed of £280. The pump was about £80 + VAT from BMW the rest being labour, testing and and new coolant. I have used these guys for years and can only assume they were fair on the labour - I was lead to believe its a bit fiddly to get to - certainly looks it - but im no expert! Old pump looked pretty dead!.... So certainly have your wits about you - check coolant level regular and keep eyes open for little wisps of steam from under the hood - I had noticed this several days prior - but due to very wet roads assumed it was to be expected - it was however said pump on the way out! - good luck - get her checked out. Regards.

Thank you so much Florio. Your advice has been invaluable to me. I am getting every single warning that you have described...had steam coming from under the bonnet around the headlamp area this morning and coolant seems to be constanly low. I am also sick and tired of being sat in a freezing cold car every day on the way to work, with only a heated seat keeping me from frostbite! I shall prepare the wallet for £300 of costs! Thank you again my friend.

Does sound extremely similar to me rivvaroom. I have also had the heater control valve go in the past......can't really remember the deal with that one but wasn't hideous (didn't have steam or coolant loss with that mind)
If you remember - get to work (engine hot) lift hood and have a look where it resides (top right handside of engine bay) and just see if you can see the early signs of leakage - obviously on a cold day this will be pretty obvious in the form of steam. Or forget that and just get it into the garage and pressure tested! I think I might be right in saying that a leak from somewhere else causing the coolant level to drop may also cause heating problems if the pump isn't being fed sufficiently (don't quote me on that though)..... think yourself lucky - sadly my sports seats are not heated!! and yep it was cold in there (prior to being fixed)! Regards

Thank you so much Florio. Your advice has been invaluable to me. I am getting every single warning that you have described...had steam coming from under the bonnet around the headlamp area this morning and coolant seems to be constanly low. I am also sick and tired of being sat in a freezing cold car every day on the way to work, with only a heated seat keeping me from frostbite! I shall prepare the wallet for £300 of costs! Thank you again my friend.

Rivva................save the 300 quid and do it yourself. Not a difficult job if you have ANY DIY experience..............the whole job should take less than an hour..........

Just a thinking here....but is your little knob, located at the bottom of your center vents, turned to the 'red' dot?
Hope this helps,
P. Ford

I always wondered what they were for... grin ... guess I'll check that this afternoon...
Does that influence what comes out under the dash to the floor?
Or would I just be chillin and warming at the same time?
Also, should I keep the snowflake icon button on?... friend told me that it dries the air
Yo, thanks man,
Rod

...if you have stuff coming out from under the dash, then I hate to tell you it is heater core replacement time (or the plastic double pipe) either way, it is E X P E N S I V E if you have the dealer do it ($2500) or time consuming if you DIY.