Heater blows cold air

[Venn77]

I have a 96 318ti with 176k on it. My heater has started blowing cool air at idle, but when I rev up to 2k-3k it blows hot air! Is this my heater core or the thermostat something else?

[TroyAndEddie]

I know this is a rolleyes reply, but low coolant is the main culprit if this is a new problem for you. It wouldn't be your thermostat, or it would be cool all the time. If the coolant level is okay, then another good possibility is just bad anti-freeze. Old coolant can deteriorate causing it to be ineffective.

[cooljess76]

follow these steps precisely to the tee:
http://www.318ti.org/forum/showthread.php?t=27983

You have what's called air-lock and need to bleed your cooling system. If not done properly and in the immediate future, you run a high risk of overheating your engine, damaging sensors, cracking your radiator and other plastic parts as well as blowing your headgasket and/or warping or cracking the head.

DO NOT JUST ADD COOLANT AND THINK EVERYTHING IS OK. Yeah, you're probably very low on coolant, but you need to bleed it every time you top it off.

[TroyAndEddie]

follow these steps precisely to the tee:
http://www.318ti.org/forum/showthread.php?t=27983

You have what's called air-lock and need to bleed your cooling system. If not done properly and in the immediate future, you run a high risk of overheating your engine, damaging sensors, cracking your radiator and other plastic parts as well as blowing your headgasket and/or warping or cracking the head.

+1.

I was just about to edit my reply, to check for air in the system as well.

[Venn77]

Thanks for all the help, I burped my car today and now have heat!