[Stratty]

Hello all,

My 2006 325xi (N52) with 130k needs a new water pump and thermostat (according to the dealership's diagnostic). They determined that the pump failed and the thermostat is stuck open. I had a few questions I wanted to probe the group about before proceeding with the replacement.

1) I noticed that after about 5-10 mins driving (in winter weather.. 20 degrees outside) my heater, started blowing cold air and then shortly after the low coolant warning kicks on. Assuming the pump failed and the thermostat is stuck OPEN, is the sudden change from hot to cold air indicative of this? (Trying to verify the dealerships diagnosis and want to be sure to account for this repeatable symptom.)

2) Would a coolant pump failure cause the thermostat to become stuck open or fail in some way? (perhaps the ECM is signaling the thermostat to stay open?) Or did the thermostat fail and I actually dont need to replace my pump at this time.

*** My Error Codes *** (also attahced)

ODB-II
P0128 - Coolant thermostat (Coolant thermostat below thermostat regulating Temperature)

INPA/K-CAN
002E81 - DME: Electrical coolant pump, speed deviation
002EF4 - DME: Map thermostat, mechanism
002E82 - DME: Electric coolant pump, cutoff


Thanks everyone in advance. I just purchased a new pump and thermostat from bavauto and plan to replace both next weekend.

[robthewrench]

You will get cold air (in the winter) any time the waterpump stops circulating coolant. The coolant in the heater core is not being replaced by hotter coolant from the engine. If the heat is coming / going, your waterpump may be cycling on/off. Cold air occurs when the pump is not pumping.

[GoRomeo]

Start shopping around for a new water pump and thermostat...

[Stratty]

Thank you guys. I figured as much. I did replace both the pump and and thermostat on saturday. I used this thread and posted a reply ...

http://www.e90post.com/forums/showthread.php?t=1089122