nothingbutbmw

So i have no heat in my car unless i run it over 2000rpms, works the best if i stay at 3000rpms.

Ive changed my waterpump and thermostat this summer, i just changed the coolant valve into the heater core as well as some hoses from radiator and coolant tank cap ( was broken ) and coolant flush but i still get no heat on idle or slow moving. On highway the heat works great aswell.

Only other thing i can think of is that my heater core is clogged? What else could be wrong that i should check?

On another note, i dont think the aux water pump is working but thats only to provide circulation after the car has been turned off correct? it should not interfere with my cabin heat after the car has been completely warmed up?

2004 545iA sport

tonyb635

OK, this probably sounds silly, but are you sure you have all the air out of the system and correct amount of water/coolant in the system ? The reason why I say this is, a friend of mine had the EXACT same problem and we fixed it by adding more water/coolant in the system. I guess it was low enough to not allow the heat to work at all when at idle and sitting at a stop light. Crazy, but its true... Ok, it wasn't a BMW and the head gasket was recently changed out but this was the system and fix.

ma_tty_d

tonyb635, +1

did you bleed the coolant system properly? the heater system might have an air bubble in the line, although if it works above 2k rpm it should have moved to the radiator which would then be noticeable.

my only other though would be that if the aux pump isn't working, it could be causing a 'block' in the coolant system to the heater? maybe it comes on at idle when the water pump isn't doing much? the water pump might be able to compensate for the resistance of the broken aux pump above 2k rpm. I'd personally start at the AUX pump and get that working if you know it isn't

nothingbutbmw

Well something is causing not enough flow in the heater core, we cant figure it out. My indy is a little stumped as well.

Today he tried getting readings from the aux pump and turning it on through the computer but he couldn't so that meant there was no communication with the aux pump, but in worst case it could mean that the ihka is bad and that is a very costly repair.


Definitely bled the system and added as much coolant as we can after the flush.

He will be trying a few things on Friday/weekend so i will keep posted but if anyone has any other ideas please chime in. Well flush and bleed the system again, at this point it cant hurt.

ma_tty_d

Good luck mate, I found a link that might help, someone bypassed their broken pump with no issues.

Running without an auxiliary water pump - Bimmerfest - BMW Forums

Different Forum though, hope I don't get in trouble!

WannaBeamer

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nothingbutbmw

Finally fixed it, turns out in these cars the aux water pump, pumps coolant through the heater core on low rpms. Unless you have a good water pump that pumps better flow than usual, you will need this for heat. After i changed it heat comes on within 2-5 minutes, really fast.

If anyone has any questions let me know