[AoS810]

Hi All,

I'm getting ready to replace the thermostat-to-head coolant hose by following Efthreeoh's DIY (https://www.e90post.com/forums/showthread.php?t=1618232) and I came across two threads from the N54 subforum regarding the plastic hose running across the top of the radiator from the coolant expansion tank that seem to plague the 335i's.

1) https://www.e90post.com/forums/showthread.php?t=935690
2) https://www.e90post.com/forums/showthread.php?t=870353

I was wondering is this an issue as well for the N51/52? I haven't come across a thread yet. I just looked at mine yesterday (2008 at almost 151K miles) and the hose seemed okay, of course I wasn't going to bend it and squeeze it though haha!

Just wanted to get feedback from the community because if I have to drain the coolant to do the aluminum bib replacement I might as well tackle this plastic hose as well.

Thanks,

- James

[Ksjohnson09]

Yes it is. I just had the pleasure of replacing a cracked radiator. When I popped off the plastic tubing it shattered. Replacement hose is like $40 from BMW so I just cut a piece of 5/16" brake line to 14" and swapped it out. $5 fix and itll never break again.

[Bufalo]

My replacement expansion tank hose arrives today, it started spitting coolant around last week. Interesting timing, huh?

[rothwem]

Yeah, mine just cracked off too. The rein version is a lot cheaper than OEM, hopefully it's not complete garbage.

[Bufalo]

So the idea that I'd quickly replace that little hose while the kids got their bath last night... that went to hell in a handbasket in no time flat. The nipple on the upper radiator hose broke off in my hand before I even knew its hose clamp was loose. Oh well. I've got a whole new upper hose in transit from Amazon and am in a borrowed car for the day.

I remember the "quick" disconnect hoses being a pain in the sack when I replaced the water pump and thermostat in my old X3, and so I was terrified that I'd destroy the neck connector on my radiator when taking this apart; it's made of the same shitty aged plastic as the rest of the system. Thankfully, that was not the case. Whew.

[AoS810]

Originally Posted by Bufalo

So the idea that I'd quickly replace that little hose while the kids got their bath last night... that went to hell in a handbasket in no time flat. The nipple on the upper radiator hose broke off in my hand before I even knew its hose clamp was loose.

This was a huge concern of mine when debating whether to just replace the middle section with brake line/clamps route or replace the entire hose.. Definitely leaning towards the brake line route so I don't break the upper radiator hose while fiddling with it.

[Bufalo]

New upper hose arrived yesterday, and everything is back to normal again. Good lukc with simpler fixes, everyone.

[AoS810]

Question, for our N51/N52 engines with the magnesium/aluminum block.. do we need to be keep in mind the material of the coolant line that we're using to replace the plastic piece?

Was thinking about picking up a nickel/copper or steel (stainless?) brake line but then remembered we have aluminum bolts throughout (i.e. engine mount braket, oil pan, etc).. am I thinking too much? Just don't want to cause any corrosive damage.

*EDIT* specifically was looking at these 2:
1) https://shop.advanceautoparts.com/p/...ke+line+5%2F16
2) https://shop.advanceautoparts.com/p/...F16+brake+line

[johnmyster]

FWIW, before you get in there, I had issues with this fitting, on the front of the motor. I think the offset bolts make it easy to cram it in there crooked and break off the o-ring lip.

BMW wanted $80 for the whole hose, which would've meant disconnecting from some really tight place under the engine. I was able to cut off the plastic and insert this...$15 from Amazon.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[Bufalo]

The expansion-tank hose doesn't contact the engine block in any way.

[AoS810]

Originally Posted by Bufalo

The expansion-tank hose doesn't contact the engine block in any way.

Gotcha, thanks for clarifying! I'm not knowledgeable enough to know if it matters whether physical contact with the engine block vs even having material in the coolant loop makes a difference.

[NiNeTyOne]

Originally Posted by johnmyster

FWIW, before you get in there, I had issues with this fitting, on the front of the motor. I think the offset bolts make it easy to cram it in there crooked and break off the o-ring lip.

BMW wanted $80 for the whole hose, which would've meant disconnecting from some really tight place under the engine. I was able to cut off the plastic and insert this...$15 from Amazon.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I replaced my fitting with this part as well, it works fantastic. I used an Oetiker clamp at the top to secure the hose and it has never leaked. Been in there two years now.

This is a highly advisable mod, and even if I have to replace the hose itself at some point, I will use this fitting, it's FAR superior to the BMW part.

[The Nightman]

Originally Posted by AoS810

Question, for our N51/N52 engines with the magnesium/aluminum block.. do we need to be keep in mind the material of the coolant line that we're using to replace the plastic piece?

Was thinking about picking up a nickel/copper or steel (stainless?) brake line but then remembered we have aluminum bolts throughout (i.e. engine mount braket, oil pan, etc).. am I thinking too much? Just don't want to cause any corrosive damage.

*EDIT* specifically was looking at these 2:
1) https://shop.advanceautoparts.com/p/...ke+line+5%2F16
2) https://shop.advanceautoparts.com/p/...F16+brake+line

You're technically correct - dissimilar metals in the cooling system will eventually lead to galvanic corrosion, but I'm not sure if this is a real issue or not. The coolant acts as the conductor between the metals, but it also contains inhibitors, and the small amount of material used for the vent line repair is probably negligible.

https://www.rjes.com/html/material_choice.html