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Discussion Starter #1
Merry Christmas. Got in my 08 X5 4.8i today and had a belt screech for a couple seconds on startup. Took off the under cover and found coolant on my AC belt. What is most likely to be leaking right there? It’s a tensioner, compressor, and vibration damper on that belt right? Iv been tracking a steady vibration at idle and would guess this is related. Help appreciated. Enjoy the day. I found the most coolant on the tensioner but that was also the lowest point on the belt. IMG_3536.jpg


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In my case the connection of the upper fat radiator hose to the water pump was leaking. Few drops only but enough to make it squeal.


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Discussion Starter #3 (Edited)
Thanks deroy. I still can't find this leak. It happens almost nightly but has not increased in amount of coolant leaking. Hoses are always dry. Weep hole is dry with no residue. I cannot find the source. Even looking with an extended mirror I only see where it collects. My last diagnostic would be a pressure test but I think I would be able to find the source visually if it is happening most days (I have a hard time letting it sit for a day with time to pressure test the next). I run my hands along all of the cooling hoses and connectors but they are always dry. I recently replaced the coolant temperature sensor o-ring and that is still good. I think this leak became more pronounced when the temp sensor o-ring was replaced. Did stopping one leak create another leak further down the line?I am open to suggestions. Coolant still seems to collect on the ac belt tensioner (on the inside edge). Seeing that there may be more leaking after a longer drive, it makes me think it is a hose connection. Am I on to the pressure test or am I missing something?
 

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Did you check the weep hole on the engine block or weep hole on water pump?
On the N62, there is a weep hole on the front of the engine block. I believe it is on the left. Its purpose is to let coolant from failed valley pan pipe o-ring escape. This is yet another weak point of this engine.
Google search for weep hole

If this is your problem, there are several repair kits out there that save time compared to the BMW procedure. AGA is one although it is pricey (see link), there are cheaper ones out there if you search.
FCP Euro AGA Kit


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Discussion Starter #6
Yes. The valley pan and cylinder head vent hose is leaking. The smaller tube at the valley pan o-ring is also leaking. The valley tube weep hole is wet. Whenever I checked, it was never wet from the weep hole. I must not have checked at the right times or it did not leave noticeable residue. Their pressure test found all of this.
 
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