08 Z4, what is the deal with overflow rad tank going bad?

[2008si]

Mine is not leaking or the like on my 08 3.0si but I have seen it out on the net when I have been googling various things about this car.
Should I be worried about it leaking? The car only has 57k miles on it, mostly garage kept for all those miles, living in not terribly hot parts of the USA.
How hard of a repair/preventive repair is this? How much are replacement tanks?

[rsutoratosu]

Photos towards bottom, I end up replacing a bunch of hoses with it..
https://www.zpost.com/forums/showthr...t=coolant+leak

On top of that I did the belt tensioner and the belt at the same time, since it was all together.. I didnt do the water pump but can easily do it if I need to..

Most were bmw oem parts, use substitute when it was out of stock, I used fcp euro, life time warranty on partys.

Besides brakes.. this is the most expensive maintenance out of warranty I did so far on 2007 car

14.89 - Belt - Purchase 2018
45.59 - Tensioner
61.44 - Coolant x3 bottles
10.00 - Distilled water x4 bottles
111.83 - Expansion tank #17117573751
19.08 - Cap #17117639022
57.99 - Mahle Thermostat
64.78 - Hose #17127545263
64.78 - Hose #17127537717
4.65 - O Ring #11537545278
1.38 - Clamp #07129952119 x2
67.37 - Hose #11537545890
51.81 - Hose #11537521049
25.00 - Bib for Hose #11537545890 - End up not using
13.99 - Fan Switch Sensor #13621433077
74.50 - Hose #17127545277
13.59 - Coolant Sensor #17137553919
37.95 - Mahle Automatic Oil Cooler Thermostat #17111437362 - Recommended

[rsutoratosu]

Comes out to 699.66 + tax, I only use one bottle of coolant mix with 1 gal of water. I order 3 for top off and future work

[Our03z4]

Originally Posted by 2008si

Mine is not leaking or the like on my 08 3.0si but I have seen it out on the net when I have been googling various things about this car.
Should I be worried about it leaking? The car only has 57k miles on it, mostly garage kept for all those miles, living in not terribly hot parts of the USA.
How hard of a repair/preventive repair is this? How much are replacement tanks?

Yes, you should be worried at your cars age. Trust me, both of my z4s blew their coolant towers not long after buying them. The tank is cheap from ECS Tuning, like $70 cheap, and with all the little bits can be done for around $120 -150 if done by you. Not hard to do just messy. Don't wait on this, it will give out with out warning and then you'll need a tow costing more than the repair. Just a reminder that this isn't an over flow tank like most cars, it's a pressurized coolant tower. If it has a leak it can tear and blow with out warning. Also remember to use OEM blue coolant not the green stuff from the parts store.

[rsutoratosu]

Similar issue.. good read on whats ahead..

https://www.zpost.com/forums/showthread.php?t=1284903

[2008si]

Mine is not doing anything yet, no leaks, rad fluid at level it should be. Just was curious about this specific issue these can have.

[rsutoratosu]

Its one of those things that can go any day.. mine lasted 12 years before failure.. so either you fix it now or fix it when it breaks. I fixed mine after I saw the pool of coolant when I got home one day...