[lowrydr310]

Last year my 335i expansion tank was leaking at the top seam so I replaced it with a Rein tank and Febi-Bilstein cap. I noticed it never sealed tightly and recently confirmed that there's a small leak when the system is pressurized, resulting in some minor coolant loss, about 4oz every few months. The new Rein upper radiator hose is also leaking slightly, but not as bad as the cap connection on the tank.

Thinking it was the o-ring or cap, I swapped the cap with the OEM BMW cap from my 06 330i and the OEM cap also screws on easily with virtually no resistance. That swapped febi-bilstein cap fits and seals perfectly on the 330i expansion tank, which is also OEM BMW (just like the cap before I swapped them.)

Both caps fit tightly and seal on the BMW tank. Both caps are loose and leaking on the Rein tank.

So it appears the Rein expansion tank opening on my 335 is not properly sized and allowing the system to leak. Fortunately I bought it from FCP so I'll be filing a warranty claim.

[StradaRedlands]

Another knock against Rein... they're becoming a no-go manufacturer.
Do they even make their own parts, or just put third party junk in their boxes?

[3PedalJake]

I also had a problem with a Rein radiator hose only mine never had a chance to leak, it was too tight to get the fittings connected. FCP replaced it and 2 was the charm because it's been in there leak free. I've been trying to avoid that brand unless I can't source any other.

[3PedalJake]

Originally Posted by StradaRedlands

Another knock against Rein... they're becoming a no-go manufacturer.
Do they even make their own parts, or just put third party junk in their boxes?

Ever watch those Pakistani videos where they make everything under the sun while sitting in the dirt wearing sandals? Waiting to see a stack of Rein boxes in one of them. Not knocking those guys they make everything, and do it with Flintstones era tools, don't think I want them making my critical car parts tho.

[GoRomeo]

When I fisrt bought my E88, the expansion tank started leaking badly. I went straight to the dealership and bought OEM expansion tank and Cap. It has been a year. No issues.

My E90 still running on original expansion tank. Its 18 yrs old. Even though the floating stick broke, the tank still holding off pretty good.😊. I did replace the cap last year since I read these caps are the main cause the expansion tanks blow up due to caps not releasing pressure.

Cheers 🍻

[Bims328i]

Yeap, I've had issues with Rein fitment on some parts. Their bolts seem to be ok but I paired a Rein upper expansion tank line with a genuine expansion tank replacement, and it was loose as hell on the connection point.

Not sure if it was due to the o-ring getting flattened but it was connected to the original tank at first in which it fit well.

To address the loose connection I used plumbers tape on the tank connection port and it has been holding fine since.

[M-technik-3]

I bought a rein as well for my E81 and ended up sending it back, Had to send the radiator back as well that leaked from the lower right corner. But that was a Mahle unit.