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7 Series - E65 / E66 (2002 - 2008)
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  #1  
Old 07-22-2014, 04:42 AM
Angelus666 Angelus666 is offline
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[760LIA]Expansion tank coolant broken

Hi everybody

I had a problem on my car (BMW 760LI 2003, 111k Miles) during my holidays.In france (like other country of course), we have hot temperature currently.
So i was driving in city, and i parked on a street. I shutdown the engine. And after that, my expansion tank has "exploded", white smoke from the expansion tank.

I've call a truck to bring my car to the close garage. Now my 760li is currently in reparation, the expansion tank will be changed.

I'm pretty sure that the expansion tank failure is the consequence of something, but what?

The A/C was on before that i shutdown the engine. But no light on my panel came up to say "hey, i'm so hot".

Moreover, i have no heard the electric fan switch. When this specific fan must activated?
When i turn on the A/C, the electric fan is still off, it's normal or not?

thanks for you reply
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  #2  
Old 07-22-2014, 06:12 AM
new760Liowner new760Liowner is offline
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Tank explosion likely caused by high pressure coupled with thermal degradation of the plastic over time.


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Old 07-22-2014, 06:24 AM
Angelus666 Angelus666 is offline
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Hi,
Thanks for your answer I agree with you. But when a high pressure exist, the electric fan need to be activated no? because high pressure means High temperature of the coolant liquid
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Old 07-22-2014, 08:48 AM
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First_745Li First_745Li is offline
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It didn't overheat, it's plastic over time it just goes "pop".


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Old 07-22-2014, 10:49 AM
HerbP HerbP is offline
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The expansion tank failure is very common. The sensor at the lower radiator hose, controls the cooling fan operation. If the sensor does not measure any water temp, the fan will not turn on. If you still have a problem with the fan after replacing the expansion tank, have someone run the diagnostics on the fan. It has 4 speeds, & it turns on based on the engine's temp. The cooling fan could be bad, & it is around a 500.00 part.

Hope this helps
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Old 07-22-2014, 12:17 PM
Angelus666 Angelus666 is offline
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Hi HerbP, thanks for you answer,

it is reassuring , so i've order the fan swicth radiator sensor, is not really expensive. It's the number 3 of the below schema? This is sensor that you speak?

[IMG][/IMG]
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Old 07-22-2014, 03:38 PM
TechFreak TechFreak is offline
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Quote:
Originally Posted by First_745Li View Post
It didn't overheat, it's plastic over time it just goes "pop".


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First745Li is right ...i had to change mine as it was leaking a few years ago.

The expansion tank looks like its manufactured in two halves and has a super strong bonding that glues them together.

The leak in mine was a crack in the bonding....i noticed the leak when the engine was cold so who knows what would have happened at high temp.

Super easy to replace yourself though....just don't do it when its hot...lol
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Old 07-23-2014, 01:14 AM
Angelus666 Angelus666 is offline
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Hi TechFreak,

Thank you for your answer . I know that it's easy to replace, but in my case it was impossible for me to change the piece because i fell down at 5 hour of road of my home, so i was obliged to put my car to a garage . 400 dollars of reparation
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  #9  
Old 07-25-2014, 09:17 PM
Busarider Busarider is offline
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The expansion tank should not blow out rather the cap should release pressure first like a safety valve. I think the cap was defective n hence the tank blowing.
I had a small hairline crack as well and replaced it a cpl of months ago, very easy but make sure you drain out the coolant first otherwise it will spill all over.
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Old 07-28-2014, 01:22 AM
Angelus666 Angelus666 is offline
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Hi,

I got my car from the garage, my expansion tank is new

I have a suitcase diagnostic and i have a default on the electric fan. I have the error code 279D : "Output stage Electric fan. Short circuit to ground".
Now i know that my electric fan is dead.
How can i unmount the electric fan? What is the different step? It is complicated?

Last edited by Angelus666; 07-28-2014 at 02:57 AM.
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