Let's talk about M54 coolant expansion tanks
 

Well, Merry Christmas. :banghead: Got a low coolant light warning tonight when I went to run an errand. Engine cold and backing out of the drive so shut it down and added about a cup or so to bring the float just off the bottom. Thought that's weird, I just did the pump a few weeks ago and I bled the system and knew if was full. Ran my errand and sure enough, she's leaking underneath. Took the airbox off and the underneath splash tray and found the common cracked expansion tank.

I have the M54 3.0L with automatic transmission so the plan is new Genuine BMW ET, automatic thermostat and cap. For those of you that have had the same drama, am I over looking anything?

- Search for the "partial cooling overhaul DIY" I wrote a while back when my 2006 X5 M54 was at 115K: Wahler tstat, reservoir, tstat, cap, belts, pulleys, fan clutch etc.

- If you have more than > 150K, then do a entire cooling overhaul.

- The reservoir, use BMW only. Interestingly, I bought this from a BMW dealer, who is trying the get rid of old stock for cheap. Normally, the reservoir is $100 or so, this (Century Auto BMW dealer) is selling it for $55:

https://www.ebay.com/itm/Genuine-BMW...1/122630659270

I keep my X5 pretty nice and I just did the belts, tensioners, idler pulley and water pump. I had a soft fail thermostat last year so that was done then. The hoses look really good so I think I will leave those for now. I may end up buying a new level sensor since I have the tank out. I know the transmission thermostats always tend to come apart when you pull the tank so I have that on my list.

Any other suggestions I am all ears.

https://xoutpost.com/attachments/x5-...422_192143.jpg

https://xoutpost.com/attachments/x5-...422_192130.jpg

My reservoir came with the trans thermostat. It's a pretty easy job to ride the tank. I used a non OEM parts but it seems well made I just needed an instant fix and could get the copy cat from local store


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FML. I have a flight Monday at noon if it doesn't get cancelled. I have to be on track in Daytona Tuesday morning and thinking about running to the stealership first thing Monday morning and get this done. We are supposed to see 8" of snow and ice tonight and I now it's not much for you up there but it paralyzes Charlotte. I may have to drive and the E46 on Pilot Sports will be freaking scary to try to drive... I may have to fix the X and hit the icy road.

Just did this 1 year ago on our 2005 3.0i with 100k.
I went for a Behr expansion tank... it weights a lot less then the OEM one = will fail sooner and leaked from the bottom o-ring after a few months. So... if could go back in time I would definetly go with the OEM one. And Yes, transmission thermostat needs to be replaced at the same time... came out broken as expected.
I would start to replace all the hoses only when one starts to leak...

The OEM for the expansion tank is Modine, BTW.

Good to know. Noted, thank you. :thumbup:

They always fail at the most inconvenient times... always...

Mishimoto used to make an m54 expansion tank that was all aluminum. The problem is: that tank won't fail, but something else in the chain will if you don't lower the abnormally high temp and pressure our systems run at to get that ULEV certification.


If everything in the system was metal, you would probably have to do hoses more frequently, but your tstat and expansion tank would not be the weakest links in the chain.