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2Addicts | BMW 2-Series forum Technical Topics N55 (M235i) Engine, Transmission, Exhaust, Tuning 2015 M235i overtemp warning

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      11-06-2020, 10:14 PM   #1
MBlaster
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2015 M235i overtemp warning

Fall temps in GA, car setting idle for roughly 15 minutes and I had the amber high temp indicator come on. First time seeing this and turned the car off immediately. The car has about 50k miles on it and from some of the other posts, it sounds as if it's going to be the fan or possibly the water pump. I've got some detective work to do to narrow it down to one or the other. The question I have is, are there any YouTube videos out there on how to replace the water pump and thermostat on this car. I couldn't find one but, maybe someone else out there had better luck. Thx
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      11-07-2020, 12:44 AM   #2
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Water pump would be a good guess. If you're going to replace the water pump do the thermostat as well. There are diy's on YouTube.
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      11-07-2020, 08:40 AM   #3
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Originally Posted by Mark.h View Post
Water pump would be a good guess. If you're going to replace the water pump do the thermostat as well. There are diy's on YouTube.
Yeah, definitely would change both at the same time. I couldn't find a diy video for the m235i but, I did see some specific to N55. Would the procedure be the same for all vehicles that have the N55 power plant?
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      11-07-2020, 10:02 PM   #4
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Can't say for certain. But my guess would be yes. Good luck with the install if you decide to take on the task yourself. Update us with how it goes. I've heard mixed reviews. Obviously depends on an individuals capabilities, but some say it's not too bad others say it can be a pain.
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      11-08-2020, 12:04 PM   #5
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Can't say for certain. But my guess would be yes. Good luck with the install if you decide to take on the task yourself. Update us with how it goes. I've heard mixed reviews. Obviously depends on an individuals capabilities, but some say it's not too bad others say it can be a pain.
So, tried to replicate what happened two days ago while watching the fan and checking for the amber warning. After running in place for awhile then, turning on the AC, I was finally able to get the fan to move. The fan wouldn't just kick in and run for some time and kick back out, it would jog back and forth for a few seconds then stop and maybe repeat once more before stopping completely. During the jogging, it might complete a single revolution, maybe. After witnessing this for 5 to 7 minutes, I finally got an excessive heat warning which was different than the warning two days ago. To me, before getting the excessive heat warning, I would have expected the fan to kick in continuous and attempt to cool things down. Given the fan motor jogging back and forth, this doesn't sound normal so, is it the fan or the fan control circuitry? I've ordered an OBD2 to BT adaptor and will down load an app for my iPhone or one of my older android phones, I'm tired of guessing what's going on with important engine metrics.
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      11-10-2020, 06:15 PM   #6
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Water pump and thermostat as mentioned earlier. OEM coolant only.
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      11-11-2020, 11:38 AM   #7
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I would be pulling some codes before replacing any parts. these cars aren't cheap to repair to just start throwing parts at it until something fixes it. could be the fan its self, could also be a software issue with the dme since the dme is what triggers the fan or could even be a dme its self. I doubt that it's a coolant pump just because the fan would generally be in full blast if you has a coolant pump low turbine speed fault. Find what the faults are first and post it up. if you got to do any driving with it I would suggest putting the cabin temp to full hot to help keep engine temps down
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      11-12-2020, 08:58 AM   #8
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Originally Posted by Taunto View Post
I would be pulling some codes before replacing any parts. these cars aren't cheap to repair to just start throwing parts at it until something fixes it. could be the fan its self, could also be a software issue with the dme since the dme is what triggers the fan or could even be a dme its self. I doubt that it's a coolant pump just because the fan would generally be in full blast if you has a coolant pump low turbine speed fault. Find what the faults are first and post it up. if you got to do any driving with it I would suggest putting the cabin temp to full hot to help keep engine temps down
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I would be pulling some codes before replacing any parts. these cars aren't cheap to repair to just start throwing parts at it until something fixes it. could be the fan its self, could also be a software issue with the dme since the dme is what triggers the fan or could even be a dme its self. I doubt that it's a coolant pump just because the fan would generally be in full blast if you has a coolant pump low turbine speed fault. Find what the faults are first and post it up. if you got to do any driving with it I would suggest putting the cabin temp to full hot to help keep engine temps down
There is no CEL so, what codes are you referring to? Regarding the car, I had just recently loaded BM3 93 octane Stage 1 tune. Considering reloading the stock tune and see if I can replicate the fan issue. Thx
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      11-12-2020, 09:10 PM   #9
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Quote:
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Quote:
Originally Posted by Taunto View Post
I would be pulling some codes before replacing any parts. these cars aren't cheap to repair to just start throwing parts at it until something fixes it. could be the fan its self, could also be a software issue with the dme since the dme is what triggers the fan or could even be a dme its self. I doubt that it's a coolant pump just because the fan would generally be in full blast if you has a coolant pump low turbine speed fault. Find what the faults are first and post it up. if you got to do any driving with it I would suggest putting the cabin temp to full hot to help keep engine temps down
Quote:
Originally Posted by Taunto View Post
I would be pulling some codes before replacing any parts. these cars aren't cheap to repair to just start throwing parts at it until something fixes it. could be the fan its self, could also be a software issue with the dme since the dme is what triggers the fan or could even be a dme its self. I doubt that it's a coolant pump just because the fan would generally be in full blast if you has a coolant pump low turbine speed fault. Find what the faults are first and post it up. if you got to do any driving with it I would suggest putting the cabin temp to full hot to help keep engine temps down
There is no CEL so, what codes are you referring to? Regarding the car, I had just recently loaded BM3 93 octane Stage 1 tune. Considering reloading the stock tune and see if I can replicate the fan issue. Thx
So, I finally received the OBD2 to BT adaptor and down loaded an app to monitor temps. The coolant would run up to 240f then, the fan kicked in and called it down to 220f before kicking out. After several minutes, it was heating up again but, this time it passed 240f and even exceeded 250f with no fan, just jogging back and forth until the warning came on. As mentioned, I have BM3 loaded with Stage 1 and wanted to rule it out as a problem so, flashed back to stock. The first temp cycle was promising, the fan kicked in, dropped the temp to 219f and held it there for 5 minutes and then it started climbing and didn't stop. No difference in stock and Stage 1. I just ordered a repair manual and will use it for continued diagnostics.
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      11-16-2020, 08:53 AM   #10
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first thing i would check is the cooling fans manually spin them feel for any binding listen for any grinding noise. if they dont spin freely and noise free there is a problem. Next unplug the power connectors and apply 12 volts to the fan motor to see if it spins up to speed again look and listen. If these check out its time to look at the wiring to see if there is a fault there. I cant speak for how bmw wires these, most cars use a signal from a temp sensor to a relay to handle the work load of switching power on to the fan. It shouldnt take you more than a few minutes to run these checks. a quick tstat check is once the car has warmed up say around the 200 deg mark the upper and lower coolant hoses should both be hot to the touch or use an IR temp thermometer to check if you cant safely get to the houses.

Last edited by pmcmtnbkr; 11-21-2020 at 08:01 AM..
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      11-18-2020, 07:41 PM   #11
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A bit of research in the repair manual which doesn't seem to have a TOC, I found that the DME feeds WPM signals to the electronics in the cooling fan which allows for varying fan speed. The fan spins freely and consistently kicks in once aed t about 228f and cools the temp down to about 216f before dropping out. From there, it consistently does not ever come back on but will jog back and forth which it was doing before the first complete cooling cycle. I was monitoring the fan relay the whole time which appears to kick in and provide battery voltage shortly after vehicle startup which means, the fan functionality seems to rely on the WPM signal from the DME exclusively. From what I can tell, I suspect the issue is the fan circuitry but, I would love to have this tested before dropping all that money on a new fan assembly.
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      11-19-2020, 11:05 PM   #12
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Quote:
Originally Posted by MBlaster View Post
Quote:
Originally Posted by Taunto View Post
I would be pulling some codes before replacing any parts. these cars aren't cheap to repair to just start throwing parts at it until something fixes it. could be the fan its self, could also be a software issue with the dme since the dme is what triggers the fan or could even be a dme its self. I doubt that it's a coolant pump just because the fan would generally be in full blast if you has a coolant pump low turbine speed fault. Find what the faults are first and post it up. if you got to do any driving with it I would suggest putting the cabin temp to full hot to help keep engine temps down
Quote:
Originally Posted by Taunto View Post
I would be pulling some codes before replacing any parts. these cars aren't cheap to repair to just start throwing parts at it until something fixes it. could be the fan its self, could also be a software issue with the dme since the dme is what triggers the fan or could even be a dme its self. I doubt that it's a coolant pump just because the fan would generally be in full blast if you has a coolant pump low turbine speed fault. Find what the faults are first and post it up. if you got to do any driving with it I would suggest putting the cabin temp to full hot to help keep engine temps down
There is no CEL so, what codes are you referring to? Regarding the car, I had just recently loaded BM3 93 octane Stage 1 tune. Considering reloading the stock tune and see if I can replicate the fan issue. Thx
sorry for the delayed reply.
vehicle will still set faults without triggering a c.e.l or control message.
if the fan is turning on from the DME triggering it, then I would rule out the fan.
reading codes im talking about DTC Codes. generally you will find a coolant pump turbine speed fault code stored. thats where I would be looking.
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      11-20-2020, 10:25 PM   #13
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Just as I had suspected. Since the fan was not functioning in a consistent manner, I suspected it was a fan issue but, was not sure enough to pull the trigger on a fan assembly purchase. I scheduled the local dealer to run the diag check and they did find the fan to be faulty. Since they have the car, I'm just having them replace the fan assembly so I can get the car back on the road ASAP. I know, with about 47k miles on the car, I'll probably be replacing the water pump within a year or so but, at least there are videos on replacing that. I would definitely like to have the diag tool to see these trouble codes for future use.
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      11-21-2020, 08:04 AM   #14
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Quote:
Originally Posted by MBlaster View Post
Just as I had suspected. Since the fan was not functioning in a consistent manner, I suspected it was a fan issue but, was not sure enough to pull the trigger on a fan assembly purchase. I scheduled the local dealer to run the diag check and they did find the fan to be faulty. Since they have the car, I'm just having them replace the fan assembly so I can get the car back on the road ASAP. I know, with about 47k miles on the car, I'll probably be replacing the water pump within a year or so but, at least there are videos on replacing that. I would definitely like to have the diag tool to see these trouble codes for future use.
Glad you found it! I was shocked at the cost of a fan assembly for these cars. I have to keep reminding myself I am no longer doing repair work on a honda civic
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      11-21-2020, 07:35 PM   #15
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Thanks. Yeah, had I been more patient, I would have purchased an aftermarket fan assembly and attempted to replace it myself, blind. Still would be interested in the app and dongle that would allow me to perform my own diagnostics at the same level as what the dealer had.
BTW, got a loaner 2020 330i, lots of tech but, miss the fun/power of my m235i.
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      11-21-2020, 08:37 PM   #16
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Quote:
Originally Posted by MBlaster View Post
Just as I had suspected. Since the fan was not functioning in a consistent manner, I suspected it was a fan issue but, was not sure enough to pull the trigger on a fan assembly purchase. I scheduled the local dealer to run the diag check and they did find the fan to be faulty. Since they have the car, I'm just having them replace the fan assembly so I can get the car back on the road ASAP. I know, with about 47k miles on the car, I'll probably be replacing the water pump within a year or so but, at least there are videos on replacing that. I would definitely like to have the diag tool to see these trouble codes for future use.
Happy you found the issue.
Another thing for your BM3 Stage 1, I will recommend to get an intercooler if you don't already have one.
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      11-21-2020, 09:36 PM   #17
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Quote:
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Quote:
Originally Posted by MBlaster View Post
Just as I had suspected. Since the fan was not functioning in a consistent manner, I suspected it was a fan issue but, was not sure enough to pull the trigger on a fan assembly purchase. I scheduled the local dealer to run the diag check and they did find the fan to be faulty. Since they have the car, I'm just having them replace the fan assembly so I can get the car back on the road ASAP. I know, with about 47k miles on the car, I'll probably be replacing the water pump within a year or so but, at least there are videos on replacing that. I would definitely like to have the diag tool to see these trouble codes for future use.
Happy you found the issue.
Another thing for your BM3 Stage 1, I will recommend to get an intercooler if you don't already have one.
Looking to replace the stock IC this coming Spring/Summer but, also considering putting that money toward a LSD. Just can't wait to get the car back, reflash and enjoy.
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