odd heater temp problems.

[marrow]

When I purchased my used 96 318ti several months ago, the temp needle was reliably just a needle width above dead center and the hot air from the dash was very hot. Since we had a 20 below (F) about two weeks ago, the car no longer blows hot air and just yesterday I noticed the coolant temp gauge suddenly jumps up about a quarter of the gauge or down a quarter of the gauge typically depending on whether I am moving ( lower) or stuck at a light. Higher at the light. The coolant was replaced at the end of the summer according to service records. The car hasnt actually overheated, I made it home and temp is fine at highway speeds. If this was one of my old cars, I would replace the thermostat, thinking it is sticky, coolant does not seem low and it was bmw coolant they used last time. However this is my first BMW and I want to make sure I do it right. The temp needle was moving really fast and jerky which I have never seen before. Could someone give me a list of things to do in order they should be done to solve this. I have read the previous threads and am thinking thermostat, bleed cooling system and go from there.

[mohaughn]

If the car will not fully warm up in cold weather, or if the needle moves around based on if it is moving or not, but still stays under the normal heat line, the thermostat needs to be replaced.

[Junk]

well i had air bubbles in another car that was not bled properly and when I turned on the freeway, the hot air bubble must have moved to the temp sender spot and my guage would go full hot, then be normal again.

maybe the guage is taking dump..(hey, maybe a good time to do the bmw guage check (hold odo button and key on))

I think the heater bypasses the thermostat? maybe your heater valve is stuck? (on firewall next to booster)

maybe bad electrical connection somewhere? I wouldn't think it would normally jump so fast (other than being an air bubble that moves into place and out again)

[marrow]

The car warms up fully but it does not produce hot air out the vents. My concern is that the temp seems to go hot suddenly if the car is stuck in stop and go traffic. The car has 150,000 + miles. I am guessing the coolant should all be replaced since I have to drain the radiator to do this. Wow things add up fast. Thanks for all your help.

ok last september a new water pump, thermostat and fresh bmw anti-freeze was put in and the the whole cooling system was pressure checked and inspected for leaks. In the 3 months the previous owner had the car, he sank 3600 dollars into it before selling it to me for $850. It was all payed for by his logistics company which managed a fleet for an institutional pharmaceutical service. So now I am thinking something else besides the water pump/thermostat etc. The heater valve perhaps. I will try the bleed first and see if that solves anything.Thanks for your help and guidance and any additional ideas are well appreciated.

[marrow]

The burp worked, followed the advice and got the air out and everything is working as it should. I guess I overthought the problem and had missed the cure. Thank you for all the help.

[Junk]

Wow you got a sweet deal! Although you maybe looking at a bigger problem. $3600 is a bit to sink into the car, if you get air bubbles again, then you must have a little leak somewhere. hope it's not headgasket but for $850 that would be OK. Hopefully the cold temps there (I been there once.. -70 with wind chill.. craaazy cold) maybe your heater connection cracked or seeps from somewhere. they are all made of plastic so keep your eye on it.