coolant leak wtf

[Takimo]

ok so long story short , i have this x5 since 2012, and every winter i always have a coolant leak (heater always around 32 or at least above 27) ,
after year and year of investivigation, i finally foound out that i only lose coolant when i put my heater at 32degress, but have no issue at 17 degrees.... what the fuck ?

[williamx5]

Good day!
I might be picking a little here, or maybe it's my old age, but "WTF" is okay... Spelling it out, not so much...

I would suspect you have an issue with your temp control valve by the firewall... this valve regulates the amount of hot water going thru the heater core... it might leak at wide open... IMHO, that seems to be one of the few logical reasons it would only leak at the cooler temps...

Good luck and let us know what you find!

Cheers

[Takimo]

the control valve doesnt leak, but itt might fucked up the vaccuum or let air enter in the system, i dont know... because the last few year it leak from the water pump 3 winter in a row and then expansion tank , couple plastic tube etc...when heater at 32 .... now i put 16.5 no problem...at least for now ...

bottom line is as u say it might have something to do with heater valve, can it let air in ? and then psi go up and the system cant hold pressure and part start falling ???

[StephenVA]

A quick way to find you leak is to pressurize the cooling system with a pump (see images below or find a shop that knows X5's quirks).

I think you will find that it the cold to hot cycling that is making it appear only in the colder weather.

[BimmerM3inGA]

My money says it's either part #8 or #6 in the drawing StephenVA posted (or both). Those pipes are plastic and the ends toward the front of the engine will rot out and leak. It typically only happens in cold weather, but will eventually get worse. I've replaced many of them for this exact reason.

If you know where to look, you can see coolant pooling around the junction of #8 and the side of the cylinder head. You need a bright flashlight and look between the oil filter cap and the side of the head. But it's not easy to see. And, unfortunately, it's not an easy fix. The intake manifold has to be removed. Of course, once that's done, actually replacing the pipes is a 10 minute job.

If I ever have to remove the intake from an M52TÜ or M54, I always replace those pipes - even if they look okay. They're relatively cheap and I'd hate to have to come back later since it's so easy to do with everything taken apart.

Replace BOTH pipes, even if only one is leaking. It's only a matter of time before the other goes. And the labor is the same whether you're replacing one or both.