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Old 03-20-2019, 01:12 AM
Join Date: May 2016
Location: phoenix
Posts: 2
Gerardo.57 is on a distinguished road
2005 bmw x5 4.4 Expansion Tank keeps braking

My x5 has about 140,000 miles and I notice a small leak in the tank so I replaced it with a new one, a week later I notice another leak in the tank right where my old one was so I replaced it for the second time and it began to leak agine from the same place and I also notice a small leak on the top right corner of the radiator where the water hose goes. Can someone help me out please
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Old 03-20-2019, 07:46 AM
Join Date: May 2017
Location: Colorado
Posts: 263
Attacking Mid is on a distinguished road
The most common reasons for ET failure are over-filling, age, cheap aftermarket tanks.

Buy an OE tank - either a genuine BMW or an OE Modine (FCP Euro used to sell them).

Only fill it so the top of the float stick is even with the top of the tank after properly bleeding the system.

You may want to consider buying a 1.4 bar (or 1.2) cap to lower the release pressure.

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Old 03-20-2019, 08:26 AM
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Join Date: Oct 2011
Location: NYC
Posts: 4,753
SlickGT1 is on a distinguished road
Most likely overfill and cheap expansion tank. But I am an avid believer that the 2 bar cap doesn’t help these cars survive the pressure at which your excess water should release if you overfill. You can get an e30 cap from BMW and it’s 1.4 bars.
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Old 03-20-2019, 09:16 AM
Join Date: May 2016
Location: phoenix
Posts: 2
Gerardo.57 is on a distinguished road
Yeah it's a cheap aftermarket one, it was hard to tell but I think the cap it has right now is a 200. Can you send me a link where I could but a new expansion tank?
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Old 03-20-2019, 02:56 PM
Join Date: Jun 2013
Location: Virigina, USA
Posts: 2,201
StephenVA is on a distinguished road
Way to easy

Expansion Tank BMW
Includes vent screw and leveling switch
Brand: Genuine BMW - Corporate Logo ES#: 38482 Mfg#: 17137501959
LInk: https://www.ecstuning.com/b-genuine-...k/17137501959/

Expansion Tank
Includes vent screw and leveling switch
Brand: Mahle-Behr - Corporate Logo ES#: 3023890 Mfg#: 17137501959

Stay away no - RUN from the cheap aftermarket parts. They will fail. See all the postings on Expansion tank failures from those who went before you.....

Now, regarding the leaks that you are seeing else where. The entire cooling system at 140K is on borrowed time. They have run their normal life cycle and needs a complete replacement. Either all at once or part at a time. Your car, your choice. As each part will fail one at a time in normal driving cycles, start, stop, city, Hwy.

Gather up your parts and do the job once and while your in there consider all the passageways and lines.... Just a thought and suggestion.

TIP: When you install the hoses, wipe a THIN coating of American Grease Stick SG-4 Sil-Glyde Lube Compound (4 oz Tube) https://www.amazon.com/American-Grea...SIN=B000KXJLXY on the inside hose seals. This will stop them from rolling and binding on install. Plus it keeps them flexible into the future. Works on all rubber seals like the air intake parts around the MAF sensor tube, etc.
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Last edited by StephenVA; 03-20-2019 at 03:25 PM. Reason: Warning
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