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Discussion Starter · #1 ·
I’ve been working on my new but recently old bought 2000 323i, I replaced all old coolant hoses and yet still have a mystery leak. The leak is not bad but is draining my coolant. The leak is coming from someone near the expansion tank. Components such as the expansion tank/ bracket are new as well as the water distribution pipe. Everything is new and seated correctly yet I still have a leak. Any answers to this?

Rick M
 

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Here is how I have found my last several leaks.

- Look while engine and hot and running...system under pressure.

- borrow a pressure tester and with engine off, pump up cooling system to 15-20 psi and look/listen for leaks

- buy UV coolant dye and UV glasses and flashlight. Add 1/2 bottle to expansion tank, run for 2-3 days and then, at night look with glasses and flashlight for UV leaks.
 

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2006 330 Convertible
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I had the same issue with my 2000 323ci. I kept finding dried coolant splattered up high. I replaced the expansion tank first. Nope. Then the radiator cap. Nope. Took it to a local indy shop where it was pressure tested and the upper hose was replaced. Nope. It took a long while but it finally manifested itself as a pinhole leak on a seam in the upper radiator that grew big enough to find. I could drive it on the highway (steady speeds) and have no problem - which is probably why the indy shop didn't find it. It was the constant acceleration of stop & go driving that apparently caused it to leak. I replaced the radiator (and thermostat, water pump and hoses) and never had another problem. I like the idea of UV dye mentioned above.
 

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Discussion Starter · #4 ·
Here is how I have found my last several leaks.

- Look while engine and hot and running...system under pressure.

- borrow a pressure tester and with engine off, pump up cooling system to 15-20 psi and look/listen for leaks

- buy UV coolant dye and UV glasses and flashlight. Add 1/2 bottle to expansion tank, run for 2-3 days and then, at night look with glasses and flashlight for UV leaks.
Thanks for your input. I appreciate it, I’ll give it a try and post an update in a couple days
 

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I’ve been working on my new but recently old bought 2000 323i, I replaced all old coolant hoses and yet still have a mystery leak. The leak is not bad but is draining my coolant. The leak is coming from someone near the expansion tank. Components such as the expansion tank/ bracket are new as well as the water distribution pipe. Everything is new and seated correctly yet I still have a leak. Any answers to this?

Rick M
Take it for a run to get teh pressure up in the cooling system.
Lift the car up, drop the gravel shield, get under it and look for the drips.
I am thinking ET o rings. Probably the larger one.

There's also this option:
 
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