Persistent temperature issues

okayr · 02-22-2021, 12:48 PM

Hi all,
This is my last resort. I've scoured the internet and bothered techs, I'm ready to call it quits with this. I have a 2014 X28i, it has 89k on it, and I've had a temp problem that comes and goes that's getting pretty frustrating.

About a year ago (8k mi ago too) check engine light came on code P0128. It had the thermostat replaced, I went on with life.
A week later after about 10 minutes of driving, I heard my fans were running full speed and my oil temp was still all the way down. Accelerating was bogged down as well, it felt like there was no turbo. No check engine light but P0128 pending again. Turn it off and on and magically back to normal. It also seems to only happen in colder temps. Like <55f. So throughout summer I never experience the problem.

I took it back to the shop and they replace the engine coolant sensor and sent me on my way. A week later same event occurs, couldn't get the shop to diagnose it so since I could turn it off and on and it would go away I just started to live with it. I did the coolant bleed procedure just in case there was air in the lines. Didn't do anything came back later.

Fast forward to this year, the same sequence of events started again. Cold, fans, lack of power, pending p0128. I decide to take it to a BMW-only shop hoping they would have some better insight. They found the thermostat was stuck open (surprise). Luckily the car is under a protection plan so they went and replaced the thermostat, water pump, valve cover gasket, engine oil filter housing, EVAP control canister.
I thought that would be it, it would be done, maybe it was the water pump? No! It's back. I took it back to them and they couldn't find any problem. I said, "okay, I will literally drive it to you guys while it's acting up in hopes you can diagnose it while it's happening." I drove it to them and they couldn't look at it at the moment (understandably) so it was turned off and they've had it for a couple of days now.
The people there are great and know they're trying. But I know they have to think I'm crazy. I feel crazy! I also feel like I shouldn't have to turn my car off and on and a stoplight once every few days when it's cold outside.
Any insight would be so helpful.

**UPDATE**
After two weeks they found the culprit. The transmission oil cooler will also throw P0128 if faulty! Replaced and no issues at low temperatures anymore. Stumped the shop for awhile but they seem confident this is the fix. We'll see in a year

e30lover318i · 02-22-2021, 01:34 PM

That is an odd one, sounds like you’ve had all the correct things replaced. I can tell you I did see a similar problem years ago but on an e38 740il, the problem ended up being somehow coolant traveled inside the the wires for the temp sensor and made its way into the DME and was shorting the DME out. I’ve seen something similar in Mercedes where ATF would travel inside the wires into the transmission computer and it would cause erratic codes and shifting.

e30lover318i · 02-22-2021, 01:35 PM

I’m not saying this is your problem but if the tech is scratching his head it might be something to check

BMWfan73 · 02-22-2021, 02:52 PM

I don't mean to hijack this thread, but my question is somewhat pertinent. I like to keep an eye on coolant temps and have an Ultragauge installed in my '15 Xdrive 35i MSport. What is the nominal operating temp (F) and what temp should I set an alarm to/what is danger zone? I've seen it mostly hover around 180F and as high as 203F.

okayr · 02-22-2021, 04:21 PM

Quote:

Originally Posted by e30lover318i

That is an odd one, sounds like you’ve had all the correct things replaced. I can tell you I did see a similar problem years ago but on an e38 740il, the problem ended up being somehow coolant traveled inside the the wires for the temp sensor and made its way into the DME and was shorting the DME out. I’ve seen something similar in Mercedes where ATF would travel inside the wires into the transmission computer and it would cause erratic codes and shifting.

Quote:

Originally Posted by e30lover318i

I’m not saying this is your problem but if the tech is scratching his head it might be something to check

Thanks, I'll def ask about the DME when they reach out if there's still no diagnosis. It might not be but it's still something that should be looked at. Could even be just a bad connection to the DME.

koolio202 · 03-31-2021, 11:02 PM

So I've been dealing with this exact same issue on my 2017 S28I they replaced the engine thermostat and it came back I had them tow it in and they said it was the transmission thermostat built into the trans cooler. I'm waiting for another cold day to see if it happens again.

Edit: nvm i saw they fixed the issue.

02-22-2021, 12:48 PM	#1
okayr Private First Class 32 Rep 101 Posts Drives: 2014 BMW X3 xDrive28i Join Date: Feb 2021 Location: California iTrader: (0)	Persistent temperature issues Hi all, This is my last resort. I've scoured the internet and bothered techs, I'm ready to call it quits with this. I have a 2014 X28i, it has 89k on it, and I've had a temp problem that comes and goes that's getting pretty frustrating. About a year ago (8k mi ago too) check engine light came on code P0128. It had the thermostat replaced, I went on with life. A week later after about 10 minutes of driving, I heard my fans were running full speed and my oil temp was still all the way down. Accelerating was bogged down as well, it felt like there was no turbo. No check engine light but P0128 pending again. Turn it off and on and magically back to normal. It also seems to only happen in colder temps. Like <55f. So throughout summer I never experience the problem. I took it back to the shop and they replace the engine coolant sensor and sent me on my way. A week later same event occurs, couldn't get the shop to diagnose it so since I could turn it off and on and it would go away I just started to live with it. I did the coolant bleed procedure just in case there was air in the lines. Didn't do anything came back later. Fast forward to this year, the same sequence of events started again. Cold, fans, lack of power, pending p0128. I decide to take it to a BMW-only shop hoping they would have some better insight. They found the thermostat was stuck open (surprise). Luckily the car is under a protection plan so they went and replaced the thermostat, water pump, valve cover gasket, engine oil filter housing, EVAP control canister. I thought that would be it, it would be done, maybe it was the water pump? No! It's back. I took it back to them and they couldn't find any problem. I said, "okay, I will literally drive it to you guys while it's acting up in hopes you can diagnose it while it's happening." I drove it to them and they couldn't look at it at the moment (understandably) so it was turned off and they've had it for a couple of days now. The people there are great and know they're trying. But I know they have to think I'm crazy. I feel crazy! I also feel like I shouldn't have to turn my car off and on and a stoplight once every few days when it's cold outside. Any insight would be so helpful. UPDATE After two weeks they found the culprit. The transmission oil cooler will also throw P0128 if faulty! Replaced and no issues at low temperatures anymore. Stumped the shop for awhile but they seem confident this is the fix. We'll see in a year Last edited by okayr; 03-15-2021 at 09:46 PM..
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02-22-2021, 01:34 PM	#2
e30lover318i Second Lieutenant 80 Rep 211 Posts Drives: E30,E34T,E46,F48 Join Date: Dec 2019 Location: RI iTrader: (0)	That is an odd one, sounds like you’ve had all the correct things replaced. I can tell you I did see a similar problem years ago but on an e38 740il, the problem ended up being somehow coolant traveled inside the the wires for the temp sensor and made its way into the DME and was shorting the DME out. I’ve seen something similar in Mercedes where ATF would travel inside the wires into the transmission computer and it would cause erratic codes and shifting.
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02-22-2021, 01:35 PM	#3
e30lover318i Second Lieutenant 80 Rep 211 Posts Drives: E30,E34T,E46,F48 Join Date: Dec 2019 Location: RI iTrader: (0)	I’m not saying this is your problem but if the tech is scratching his head it might be something to check
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02-22-2021, 02:52 PM	#4
BMWfan73 Lord of Glencoe 36 Rep 108 Posts Drives: '15 xDrive35i M-Sport Join Date: Aug 2020 Location: Big Sky Country, MT iTrader: (0)	I don't mean to hijack this thread, but my question is somewhat pertinent. I like to keep an eye on coolant temps and have an Ultragauge installed in my '15 Xdrive 35i MSport. What is the nominal operating temp (F) and what temp should I set an alarm to/what is danger zone? I've seen it mostly hover around 180F and as high as 203F. __________________ (OO)=[][]=(OO)
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03-31-2021, 11:02 PM	#6
koolio202 Registered 0 Rep 4 Posts Drives: bmw x3 Join Date: Mar 2021 Location: orlando fl iTrader: (0)	So I've been dealing with this exact same issue on my 2017 S28I they replaced the engine thermostat and it came back I had them tow it in and they said it was the transmission thermostat built into the trans cooler. I'm waiting for another cold day to see if it happens again. Edit: nvm i saw they fixed the issue.
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