[neilvan]

So I'm coming across from the E90 forums; We have 2 but my mother owns an 2004 X3 2.5. Its been a fairly reliable car until now. We got at around 190k KM and its now at 240k ish.

We re-did the coolant system 1.5-2 years ago; Just premature maintenance because BMW. EVERYTHING (rad, water pump, pulley, expansion tank, all hoses etc) except the expansion tank mounting plate and water-pipe connector (ordered it all and just overlooked those 2 things).

So forward to a month ago, guess what leaks... Those 2 pieces. Took a while to figure out but bought new ones. Replaced them and its still leaking; From the expansion tank connections now. Replace that and it starts leaking from the upper rad hose this time. Finally after replacing all of that it seems to fix it.

Except now its starting to weep from the upper rad hose to rad connection. AGAIN.

Is this a common thing or is there something I've been overlooking? (FYI all parts are OEM BMW or the OEM manufacturer for BMW, No cheap crap)

[frisbeeguy]

vehicle kept outside daily?

[neilvan]

Yes outside all year round; summer and winter. Toy cars get the garage. Our temps range between 30 to -10ish *C on average

[CanadaeastKTM]

Kept outside should matter, it’s a car.
Wondering if there is somehow too much pressure in the system and the parts are fine but access pressure finding it’s way out whichever which way it can. Maybe see if there is a way to test make sure thermostat working.
Have you notice if the leaking started from heavy load on the car when it got really hot (building more pressure)?

[doru]

Mine has the N52 engine, and I had to change the expansion tank and that plate, issue fixed. But now, I remember there was also the oil t-stat somewhere in there - not sure if the M54 engine has the same design. That t-stat literally disintegrated in my hands. And it's right under the exp tank where it mates with the plate. Item #11 in this diagram