[Reide92]

Hello everyone! New to the forum and BMWs, i recently bought a 2008 e92 335i MT with 53k miles.
Car is FBO with jb4 and mhd bef however i have flashed it back to stock.
Ive replaced quite a few things and while i was at it noticed the coolant was neon green so i decided to change that right away. I flushed the coolant 4 times and finally filled with Zerex G48 50/50. Bled twice after.
Was driving the car for about 3 days until it decided to overheat one day (limp mode and spilled out the expansion tank cap)
Since then ive tried rebleeding multiple times, got a code for temp sensor so i replaced the sensor, no luck.

Coolant looks fine and is full, water pump and thermostat are according to the previous owner new and appear to be working fine and the fans work, im kind of stumped!
No leaks i can find or anything and trust me ive searched.

Today i let the car idle until warm and watched coolant temps with mhd app, at idle it gets to about 221°f before the fan kicks on and maintains around that temp, but once i start driving as soon as i hear the turbos start spinning (not even boosting just spinning) the temp will rise up to 230 or 240 in around a second which seems insane to me? Could just be under light load and irrelevant to turbos. When i actually boost it doesnt change anything same rise in temperature as light load.
After i got the yellow warning limp mode really only lasted 5 secs or so, i heard the fans kick in high speed and i drove back up the hill to my house no problem.

Should i add new coolant incase theres some sort of restriction in there or is g48 possibly the issue? I couldn't find any bad info on it with n54s and again the coolant itself looks very clean.

Last thing ill add is the car never overheated before i changed coolant but it was a fair amount colder outside than it has been since this issue started.
Anyways, sorry this ran on so long, any help is appreciated, thanks!

[CALWATERBOY]

.
Do this with a BMW Capable Code Reader:

Delete all codes
Run until issue occurs
Read codes & post here

Sure, water pump reputed to be new, but [click me] anyway.

[Reide92]

Thanks for the reply, i had already cleared codes prior to driving and was only left with a 2FDB shadow code. (Crankshaft sensor signal not plausible) i havent gotten any water pump related codes but after reading that forum im leaning toward replacing that and the thermostat, not too expensive and for all i know it could be the original pump and stat.
I read somewhere you can test your pump speeds with inpa has anyone had luck with that?

[CALWATERBOY]

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Hang on - are you certain system was throughly bled?

[Reide92]

Originally Posted by CALWATERBOY

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Hang on - are you certain system was throughly bled?

Yep i bled it electronically multiple times, heat all the way up to i believe 84 or whatever fan on low with the cap off. I even tried once with the cap on because i found a video saying to leave it on which made no sense to me lol.
And i added coolant and bled again after replacing sensor. Symptoms seem like air in the system but ive bled numerous times.

[Emilime75]

Try cap on and the bleeder screw just barely cracked open to allow air to escape. You should get a little bit of coolant dribble out of it while the bleed procedure is running.

[Tyc0]

I had a similar situation when I bought my car, it would run fine for about 30 minute drive but anything farther than that it would overheat, turned out to be water pump not being able to run at 100%, new one fixed my issue. Another thing I would suggest checking is your battery voltage, these cars do weird things when they don't have the right amount of juice and I have heard the water pump does so as well. Though I'm not sure this is true it is just an easy thing to check for.

[Reide92]

Originally Posted by Tyc0

I had a similar situation when I bought my car, it would run fine for about 30 minute drive but anything farther than that it would overheat, turned out to be water pump not being able to run at 100%, new one fixed my issue. Another thing I would suggest checking is your battery voltage, these cars do weird things when they don't have the right amount of juice and I have heard the water pump does so as well. Though I'm not sure this is true it is just an easy thing to check for.

Ive read about that too, my battery seems fine i mad it through 2 coolant bleeding cycles before i had to throw a charger on, but it seems like its either that or the pump not running 100%.
I already ordered the pump kit so ill be doing it by next weekend and hopefully that does it!
Thanks!

[Reide92]

Update, solved! New battery and no more overheating 😁. Also my jb4 was giving me strange seperate issues so uninstalled that too and the cars doing great!

[Kingweddle21]

New to the forums, cant figire out how to make my own post. Im currently having a similar issue with my 2013 335i, n55. New water pump and thermostat 2 years ago now, doesnt overheat during daily driving activities. I have a cobe tuner onboard to watch coolant temp as im driving, only over heats during prolonged pulls or sustained over 4k rpm. The weird part is it does not go into limp mode, the overheating light will come on around 250-260f°, as soon as the light comes on it goes away and drops back down to normal coolant temp araound 220° and i can continue driving. Checked the coolant, pump is working, thermostat is still somewhat new, did an oil change and there was no milk. Im at a loss and cant find any forums with this problem.

[Jaronbwall]

Originally Posted by Kingweddle21

New to the forums, cant figire out how to make my own post. Im currently having a similar issue with my 2013 335i, n55. New water pump and thermostat 2 years ago now, doesnt overheat during daily driving activities. I have a cobe tuner onboard to watch coolant temp as im driving, only over heats during prolonged pulls or sustained over 4k rpm. The weird part is it does not go into limp mode, the overheating light will come on around 250-260f°, as soon as the light comes on it goes away and drops back down to normal coolant temp araound 220° and i can continue driving. Checked the coolant, pump is working, thermostat is still somewhat new, did an oil change and there was no milk. Im at a loss and cant find any forums with this problem.

Are you running an aftermarket tune? It seems like a tune related high boost situation in which you better have supporting mods (intercooler). Are you leaking coolant? Did you bleed the system? Maybe the radiator is bad or the fins are smashed. All of the above can affect the coolant and engine temps. If you're over 120k miles and haven't flushed and replaced the coolant it's time to do it. The coolant lines are shit and break over time. Ask me how I know. I'm going through cooling maintenance headaches right now. Car has been off the ground for weeks.

[Kingweddle21]

Originally Posted by Jaronbwall

Are you running an aftermarket tune? It seems like a tune related high boost situation in which you better have supporting mods (intercooler). Are you leaking coolant? Did you bleed the system? Maybe the radiator is bad or the fins are smashed. All of the above can affect the coolant and engine temps. If you're over 120k miles and haven't flushed and replaced the coolant it's time to do it. The coolant lines are shit and break over time. Ask me how I know. I'm going through cooling maintenance headaches right now. Car has been off the ground for weeks.

Im running a stage 2 plus 95 octane with the cobb. Have been for almost 3 years now, and only now having issues. After market intercooler, 3" charge pipe, step colder plugs and coil packs are about a year old now. Only leaks when the overheating light comes on, im assuming thru the overflow? It did just hit the 120k mile mark so I'll look at flushing the system soon. Budy of mine is insisting that the thermostat has failed again, im not so sure though

[Jaronbwall]

Originally Posted by Kingweddle21

Im running a stage 2 plus 95 octane with the cobb. Have been for almost 3 years now, and only now having issues. After market intercooler, 3" charge pipe, step colder plugs and coil packs are about a year old now. Only leaks when the overheating light comes on, im assuming thru the overflow? It did just hit the 120k mile mark so I'll look at flushing the system soon. Budy of mine is insisting that the thermostat has failed again, im not so sure though

Thermostat could be going out but that's questionable. If your car is leaking coolant I'd start there. Problem with these damn N54's is the plastic connections and everything gets brittle. Things get cracked really easy. I replaced my pump/thermo 4 years ago. No issues **knock on wood** with those. Fun fact; removing the lower radiator hose is a b**CH! No joke it took 15 mins, heat gun, WD-40, and hammer.
I would remove your intercooler, flush the system, refill the coolant, bleed, and see what happens. Just keep reusing the new coolant until you find the issue. That's really all you can do. haha