Pesky leak
 

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

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Roger that. 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.

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

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

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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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.