Thermostat Question

3drty5 · 07-22-2019, 10:48 AM

Hey everyone, have a quick question about my 2007 335i's thermostat.

Thermostat was replaced by the dealer at 85k miles before I bought the car, and the car now sits at 130k miles. Over the last year, I had been travelling around and was only able to drive the car once every week or once every two weeks. I have started daily driving the car again, and have noticed something weird. I live in Florida, but in early March we had an unusually cold few days (Low 50's here LOL) and I took the car out that night (ambient high 40's low 50's). Car threw a check engine light and INPA told me it was a P0128 code (coolant not up to temperature). Decided to clear it and it didn't come back. Car was driven again here and there without issues, in early may I hopped in an had a catalytic converter (1 and 2) efficiency code, cleared those as well. Was not worried about it because the car heats up the same as it always has (if not a little quicker) right up to 210 degrees F. It seems to get stuck around 210 (sometimes getting up to 220). When I was daily driving it last year, it would usually run at 230-240 degrees F.

I was thinking about replacing the thermostat, but if I'm doing all of that work I might as well replace the water pump- but seeing as these parts were replaced only 45,000 miles ago, i'm hesitant to replace the water pump seeing that it is relatively new. Is this something I should take care of immediately, and should I be worried that it is running about 20 degrees cooler than usual? As always, thank you for your help!!

Oolien · 07-23-2019, 01:16 AM

as for the po128 code there's only really a couple things that could go wrong, usually you're right its the thermostat sticking or just completely faulty but hence you continued driving it and it never came back it cant be faulty but possibly sticking hard it say cause it hasn't came back. what i would recommend doing is run the engine. then using an infrared thermometer to get the temp of the coolant at the thermostat housing inlet and outlet i believe the oem temp is like 195f if the temps are the same and below oem temp that means the thermostat is open

07-22-2019, 10:48 AM	#1
3drty5 New Member 1 Rep 12 Posts Drives: 2007 E90 335i 6MT Join Date: Sep 2017 Location: Florida, United States iTrader: (0)	Thermostat Question Hey everyone, have a quick question about my 2007 335i's thermostat. Thermostat was replaced by the dealer at 85k miles before I bought the car, and the car now sits at 130k miles. Over the last year, I had been travelling around and was only able to drive the car once every week or once every two weeks. I have started daily driving the car again, and have noticed something weird. I live in Florida, but in early March we had an unusually cold few days (Low 50's here LOL) and I took the car out that night (ambient high 40's low 50's). Car threw a check engine light and INPA told me it was a P0128 code (coolant not up to temperature). Decided to clear it and it didn't come back. Car was driven again here and there without issues, in early may I hopped in an had a catalytic converter (1 and 2) efficiency code, cleared those as well. Was not worried about it because the car heats up the same as it always has (if not a little quicker) right up to 210 degrees F. It seems to get stuck around 210 (sometimes getting up to 220). When I was daily driving it last year, it would usually run at 230-240 degrees F. I was thinking about replacing the thermostat, but if I'm doing all of that work I might as well replace the water pump- but seeing as these parts were replaced only 45,000 miles ago, i'm hesitant to replace the water pump seeing that it is relatively new. Is this something I should take care of immediately, and should I be worried that it is running about 20 degrees cooler than usual? As always, thank you for your help!!
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07-23-2019, 01:16 AM	#2
Oolien Enlisted Member 3 Rep 47 Posts Drives: 08 bmw 335xi n54 Join Date: Apr 2019 Location: canada iTrader: (0)	as for the po128 code there's only really a couple things that could go wrong, usually you're right its the thermostat sticking or just completely faulty but hence you continued driving it and it never came back it cant be faulty but possibly sticking hard it say cause it hasn't came back. what i would recommend doing is run the engine. then using an infrared thermometer to get the temp of the coolant at the thermostat housing inlet and outlet i believe the oem temp is like 195f if the temps are the same and below oem temp that means the thermostat is open
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