Pesky leak

[E39LV]

So I've had this coolant leak on my 13 e70 LCI but really slow. It finally developed more now where I could identify where it was coming from. I believe it's the bottom hose on the expansion tank.
Question: when I look down there from topside the clamp is on and it looks completely normal. What would cause a hose to leak all of the sudden like that??! I've had the vehicle a year and a half and haven't done anything coolant system related. One day about a month ago the low coolant warning came on and I replaced the couple capfuls that were missing upon inspection. Now it's a little more noticeable.
Do I replace the hose or cut an inch or so off the end depending on how much of the tip is cracked? Or is it the whole hose that has failed?


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[Zulu95]

Could be the tank. Known failure point.

[E39LV]

UUUUUURGH! Good to know.
85k? What do you think? Is the mileage around where these fail?
Thanks!

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[Zulu95]

You are in the ballpark from all I have read. But one poster claimed it is a 15 minute job to change out. So it cannot hurt to eliminate it as a possible cause of the leak and also eliminate it exploding whilst driving and stranding you at the side of the road.
GL.

[E39LV]

Roger that. Thanks!

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[ard]

Originally Posted by E39LV

UUUUUURGH! Good to know.
85k? What do you think? Is the mileage around where these fail?
Thanks!

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Probably not it.... the tanks fail about 88k or 89.








But seriously, you dont put miles on a tank. Its years.

[13brian]

Possibly small crack in reservoir tank, only openimg when hot?

[andrewwynn]

Best way to find leak is UV dye. When small enough it will evaporate before it hits the ground.

7-8 years is a little soon for the reservoir; our two e53 both suffered that fate about 18 years in

[E39LV]

It's down at the bottom area of the tank but can't see exactly where yet. Which would progress faster, a bad hose or bad tank?
Most recently I was sitting idling and it was the 1st time it left a small puddle so definitely progressed from low coolant level warning to this with topping off the tank with small amounts of coolant in between...

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[andrewwynn]

Bad hose can leak a tiny bit for years. Tank crack will typically go from a drip to catastrophic failure within a week. Seam split usually is invisible and often will hide itself in the crack and show up at the bottom.