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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 03-27-2013, 10:40 AM
JimLev JimLev is offline
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Join Date: Dec 2003
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Mein Auto: 540/6, S60 Volvo, Tribeca
540 Expansion Tank issue. Bluebee U were looking for this info

I posted this same info over on Roadfly, unless you have an account there you can't view the pics.

540 Expansion tank problem and dissection

A few weeks ago I helped a friend change his lower oil pan gasket on his 2000 540ia.
He mentioned that when driving on the highway and then needing to slow down because of traffic the heat would sometimes go cold and the temp gauge would start to rise. Throwing the car into neutral and giving it gas would bring the temp gauge back down and the heat would return.
After the oil pan gasket job was done I took the cap off the expansion tank. Looking inside the level didn't look right.
The left side of the tank was almost empty, it should be 1/2 full. This is the section that fills the waterpump/engine.
The section of the tank that the stick is in was full to the top part that the stick traverses thru. Didn't look right to me.
We dumped more coolant in even though the stick showed it was overfilled.
He ordered a new expansion tank. The previous tank was installed in '08 and was not an OEM BMW tank.
Last Sat. we installed the new tank and all is well.
We then cut the tank open to find out what the problem was. This tank seems way more complicated than it needs to be...must be the German way of doing things?
There are 4 sections inside the tank which should all be connected to each other thru openings in the lower wall partitions.
3 of them were connected, but the important section wasn't.
If you purchase a non-BMW tank pour a little water into the tank before you install it. It should run out the bottom hose connection that goes to the waterpump.
Anyone ever run into this problem before?













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  #2  
Old 03-27-2013, 12:19 PM
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Fudman Fudman is offline
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Did he drive 4-5 years with this expansion tank and this problem only happened recently?
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  #3  
Old 03-27-2013, 12:24 PM
HTK12 HTK12 is online now
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Mein Auto: E39 540i
Manufacturer of that previous expansion tank is?
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  #4  
Old 03-27-2013, 02:01 PM
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bluebee bluebee is offline
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Mein Auto: 02 BMW 525i M54 auto 130K
Thanks JimLev, for the expansion tank autopsy, and, for the picture of the passageway that was never cut out at the factory.
This information can be helpful for this thread:
- Does anyone have a BMW description of HOW the E39 M54 expansion tank actually works?

So that this information is found easily in the future, I will cross reference this thread to the existing expansion tank autopsy threads - so that we can get a better handle on how the thing works.
- Behr radiator and Behr expansion (aka surge) tank autopsy (1) (2) & request for another autopsy to understand the function of that second (black) chamber & pinned float (1)

It would be nice if someone can explain with an exploded picture HOW the expansion tanks works (at least the flow of fluid, with arrows going in and out).

I, for one, still don't understand at all how the "black" section works!
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Last edited by bluebee; 03-27-2013 at 02:23 PM.
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  #5  
Old 03-27-2013, 03:31 PM
JimLev JimLev is offline
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Mein Auto: 540/6, S60 Volvo, Tribeca
Quote:
Originally Posted by Fudman View Post
Did he drive 4-5 years with this expansion tank and this problem only happened recently?
The date on the tank was 14-04-2008. He can't remember where he got it, maybe Pelican Parts, FCP, AutoHaus, etc. There was no emblem on it, so we know it wasn't a genuine BMW part.
He remembers that the first tank they sent him started leaking and they sent him another one which he has been using for the last ~2 years. He has been putting up with this problem as he could just flip it in neutral and step on the gas which would make the temp drop back down.
If you looked at the stick in the tank it indicated the level was fine.
The replacement tank we installed last Sat. came from FCP, it was a Behr tank that was made in China.
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Old 03-27-2013, 06:12 PM
JimLev JimLev is offline
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Mein Auto: 540/6, S60 Volvo, Tribeca
Bluebee, here's a rough 2D flow diagram of the 540 tank.
There is also some back flow from the waterpump when the coolant heats up, that isn't shown.

540 Tank, click here
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  #7  
Old 03-28-2013, 06:23 AM
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bluebee bluebee is offline
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Mein Auto: 02 BMW 525i M54 auto 130K
Quote:
Originally Posted by JimLev View Post
Bluebee, here's a rough 2D flow diagram of the 540 tank
Here's that PDF as an image, so it can be seen on the screen:
Attached Thumbnails
Click image for larger version

Name:	540_expansion_tank_flow_by_JimLev.png
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Please read the suggested threads, where the best always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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  #8  
Old 03-28-2013, 05:50 PM
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bluebee bluebee is offline
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Mein Auto: 02 BMW 525i M54 auto 130K
JimLev,
So that I can compare the M54 expansion tank with the 540i expansion tank, may I ask how many openings are in your V8 expansion tank & where they go (and what direction is the flow)?

Mine, for the M54, has the following seven external openings:
  • Top
    • Filler cap (2 bar venting)
    • Filler neck (aux pump inlet pinhole?)
    • Overflow hose nipple (to radiator nipple)
    • Bleeder screw (one of two bleeder screws on the M54, the other being in the upper radiator hose near the thermostat)
  • Bottom
    • Hose 1 (to ?)
    • Hose 2 (to ?)
    • Electrical connector to the "low coolant" sensor (no fluid flow)
Given these 540i diagrams:
Would you kindly draw the flow lines on the following set of components?
(Note: You can roughly draw the lines as I can re-construct the picture once you simply connect the points with flow arrows.)

Attached Thumbnails
Click image for larger version

Name:	540_expansion_tank_flow_by_JimLev_level.png
Views:	27
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ID:	368691   Click image for larger version

Name:	540_expansion_tank_flow_by_JimLev.jpg
Views:	197
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ID:	368692  
__________________
Please read the suggested threads, where the best always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need

Last edited by bluebee; 03-28-2013 at 06:35 PM.
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