Is the Coolant Hose Flange a common issue on M57s?

[Ottopotamus]

I found out my thermostat is stuck open on my 2012 35d with 150k miles. This explains (at least partially) why I'm experiencing poor fuel economy and hopefully also explains the white smoke I'm seeing at times during idle. I plan to replace the water pump and belts along with the thermostat while I am doing it. I will also change the turbo outlet hose with the ATM hose, since it appears to be leaking.

I currently don't have any coolant leaks but while I'm doing this, have I overlooked anything else I should be doing at the same time? I noticed some people are changing the coolant hose flange, but I've only seen a couple of posts showing someone has had issues with it. Is this a common failure that I should also be changing? The cost of the part isn't too bad (~$36 for OEM), but I'm assuming I would also change out all the intake manifold gaskets that I just changed last year (or would they be reusable without an issue?). I'm also wondering if I will need to replace the o-rings on the coolant hoses. Since I didn't originally plan on doing the coolant flange, it would likely delay my start since I would like to do everything on one weekend if possible.

If I decide to change the coolant flange at a later date, can this be done without draining all the coolant?

[jbash87]

Do the CCV hose and thermostat on the transmission cooler too.
Its up to you whether you want to replace the coolant hose flange. I took a good look at mine when the manifold was off and it was fine so I didn't worry about it. I have 140k.
I also didn't replace any of the o-rings as they were in fine shape. But it wouldn't hurt to if you're ordering parts.

[Ottopotamus]

Originally Posted by jbash87

Do the CCV hose and thermostat on the transmission cooler too.
Its up to you whether you want to replace the coolant hose flange. I took a good look at mine when the manifold was off and it was fine so I didn't worry about it. I have 140k.
I also didn't replace any of the o-rings as they were in fine shape. But it wouldn't hurt to if you're ordering parts.

I'm very glad you mentioned the transmission thermostat. To be honest, I didn't even realize the transmission cooler had a thermostat. I found this thread which really emphasizes the importance: https://www.bimmerfest.com/threads/t...stion.1366837/

I'm assuming you are referring to this hose: https://www.tunemyeuro.com/ccv-hose-...-335d-aar2238/
Are you just suggesting this since it will be easier while I'm in there?

Thank you very much!

[jbash87]

Originally Posted by Ottopotamus

I'm assuming you are referring to this hose: https://www.tunemyeuro.com/ccv-hose-...-335d-aar2238/
Are you just suggesting this since it will be easier while I'm in there?

I'm suggesting because you'll be in there, it is most likely torn, or it will be when you attempt to move it. The stock hoses get very brittle at the age of your vehicle it should probably be replaced. I also have a 2012 and found mine to be torn when I did the same job you're doing.