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Discussion Starter · #1 · (Edited)
It was fine but I believe I overfilled it this morning. Drove about 5-10 miles over the period of like 5 hours. Was getting low coolant level the day before so I decided to add some. White smoke from drivers side under the hood. Realized something wasn’t right. It stopped for a second and I was a street from my house where it went off again just as bad. A strong plume of white smoke.

I parked and shut off the car, (the temp gauge started going right of the center before I made it home and parked). Thankfully i was no where near the red zone.

opened up the hood and the coolant was burning from near the expansion tank. Realized right then that the coolant probably had no where to go.

letting it cool down now, I literally replaced the ET days ago. This is the lesson learned to not rush the cooling system as it does indeed bite back.

edit:been a few hours, not visibly leaking from below.

car is a 2003 325i m54
 

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2005 330xi Auto, 2006 330ci Vert Auto
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What makes you think your brand new ET exploded? Maybe something else burst? If you overfilled the coolant and you over-pressurized the cooling system, maybe the expansion cap vented? Or maybe you have a leak somewhere?
 

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Discussion Starter · #3 ·
What makes you think your brand new ET exploded? Maybe something else burst? If you overfilled the coolant and you over-pressurized the cooling system, maybe the expansion cap vented? Or maybe you have a leak somewhere?
there was just so much smoke, and it was originally leaking bad once I had stopped the car.Its not anymore though. The smoke was kind of coming from below the expansion tank couldn’t really see but there was some liquid on top adjacent to the cap.
 

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If you just replaced it, the first thing I'd suspect is that it's just popped loose.
It's not particularly easy to get the darned thing to seat solidly up against the radiator,
and get both sides of the clips to latch.

But a more careful examination with lotsa light, and then a good bleed, is certainly in order.

t
 
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Discussion Starter · #5 ·
If you just replaced it, the first thing I'd suspect is that it's just popped loose.
It's not particularly easy to get the darned thing to seat solidly up against the radiator,
and get both sides of the clips to latch.

But a more careful examination with lotsa light, and then a good bleed, is certainly in order.

t
will definitely give it an inspection in the morning, hopefully thats all it was as it was sizzling for a good 3-4 minutes after the car was off. I was sure i had the expansion tank on properly as it clicked into place after a large pain in the ass push and play for like 20 minutes.
 

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Discussion Starter · #9 ·
Fill ET so tip of float is level with top of neck. But first tell us how you bled the system.
i have figured out it was from incorrectly bleeding the system, i forgot to open the thermostat while putting new coolant in after theET replacement. I just hope the cap released and sprayed liquid down but there was a sizzling noise.
 

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I suspect something was not seated all the way.

I've done the coolant system on my m54b30 e46 and am doing it on my m54b30 e53 right now. You have really got to be certain everything is pushed on all the way and seated tight. On all new parts putting it together can be difficult. I use coolant on the o rings to help with assembly.
 

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2002 BMW 540Ti, 2004 BMW 330i ZHP, 2001 325Ci
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yup hope OP bleed it right, I blow in the ET, fill, blow again, etc. till coolant come out of bleeder screw.
never had to add coolant again
 

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Discussion Starter · #17 ·
Sorry for the slow reply.

i forgot to open the cap and bleeder screw when turning on the thermostat. Didnt have liquid coming through the bleeder. My first mistake.
 

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Discussion Starter · #19 · (Edited)
I have been following Mangos guide on how to bleed but when the car is cold nothing will come out the bleeder screw it just overflows.

update: figured out what has gone wrong. This is my analysis of the event.

after changing expansion tank job I did not bleed it properly because I couldnt get the upper hose to fill with coolant. Thermostat wasnt open after being cool for so long (lots of rain and the job took a few days because of it. So the car was off awhile.)

i should have brought the car up to temp before bleeding.

this caused pressure buildup in the expansion tank after my drive yesterday. Causing the upper hose to pop off and shoot the coolant all over the hot engine bay.

through my efforts today I got the hose on pretty well. kept bleeder and top off while I filled coolant. realized the thermostat needed to be warmed again after the pressure popped.
I believe I will be able to bleed it the correct way in the morning considering I got it up to operating temp and circulated coolant.

sorry if this is confusing I am high and can clarify in a couple hours. Thanks.
 
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