[saqueme]

So my 330i will run low on coolant every few months, not really sure why but it has never seemed to be that big of an issue. And recently I've smelled burning coolant from the exhaust for about 30 seconds after a cold start, and then its gone. But when I was refilling the coolant, I overfilled it a little bit, and it didn't seem that bad so I just left it since I didn't have any sort of turkey baster. But ever since then, when I go drive the car and come back there is always a smallish pool of coolant under the car. I 've taken off all the shrouds and covers and still can't tell where it's coming from, everything seems dry except for a big pool of coolant sitting on the undertray under the headers. Anyone have any idea where it could be leaking from? Access to jacks is kinda limited since its in my university parking garage.

[SixSix]

Common issue on E9x cars or at least the ones I've seen and experienced a few times is the plastic radiator caps. Not a cap you can remove but the one that seals each end of the rad. Mine had a small hairline crack on the top close to were the upper coolant hose goes in. The reservoir could be leaking, maybe the hose that connects at the bottom? There's quite a few spots for coolant to be leaking on that side of the car due to the location of the waterpump and thermostat. Could also be the main water outlet on the side of the block. You'll likely have to get an inspection mirror and poke around to see exactly where it's coming from.

[E92William]

From my experience, upper rad hose, coolant outlet, spaghetti reservoir hose, radiator elbow up top, reservoir cap.

[smass]

The most common leak on an 06 will be the temp sensor O ring in the lower rad hose. It has leaked on all 3 of my 06s. Hose off the engine. Start and run it to dry everything off and build up pressure and then look for the drip.

https://www.ecstuning.com/b-uro-part...21433077s~uro/

[Efthreeoh]

You gave no history of the car, so this is a guess. Temp sensor o-ring is possible but not all configurations have the temp sensor in the lower radiator hose elbow. I'd check the thermostat-to-head flange next to the oil filter housing. It may be ready to fail. It a common issue with very old hoses. Replacement is with an aftermarket aluminum flange.

Or it could be a failing radiator drain plug. Most people do not remove them or install them correctly.

[N52chris]

Originally Posted by smass

The most common leak on an 06 will be the temp sensor O ring in the lower rad hose. It has leaked on all 3 of my 06s. Hose off the engine. Start and run it to dry everything off and build up pressure and then look for the drip.

https://www.ecstuning.com/b-uro-part...21433077s~uro/

Yup, my 06 330i leaked from here also. It's easy to spot looking down into the front of the engine bay. I ended up putting in a brand new temp sensor, but you should be able to just replace the o ring.

[saqueme]

Originally Posted by smass

The most common leak on an 06 will be the temp sensor O ring in the lower rad hose. It has leaked on all 3 of my 06s. Hose off the engine. Start and run it to dry everything off and build up pressure and then look for the drip.

https://www.ecstuning.com/b-uro-part...21433077s~uro/

I'll double check this weekend, but I believe that area was dry

[saqueme]

Originally Posted by Efthreeoh

You gave no history of the car, so this is a guess. Temp sensor o-ring is possible but not all configurations have the temp sensor in the lower radiator hose elbow. I'd check the thermostat-to-head flange next to the oil filter housing. It may be ready to fail. It a common issue with very old hoses. Replacement is with an aftermarket aluminum flange.

Or it could be a failing radiator drain plug. Most people do not remove them or install them correctly.

Right before I got the car, the water pump and pcv system was fixed. Not sure of any other major services done to it other than that.

Do you know off the top of your head which side of the car the drain plug is?

[ruimpinho]

Hi guys, I have a coolant leak on my 320D LCI (e90, N47).
It's right under the reservoir. Anyone can help me on how to fix it?
Here's a quick video on where it's leaking:

Many thanks in advance!

[E92William]

Originally Posted by ruimpinho

Hi guys, I have a coolant leak on my 320D LCI (e90, N47).
It's right under the reservoir. Anyone can help me on how to fix it?
Here's a quick video on where it's leaking:

Many thanks in advance!

I have seen posts about this before regarding the o ring in the sensor going bad and causing this leak. Could be cracked though

[ruimpinho]

Originally Posted by E92William

I have seen posts about this before regarding the o ring in the sensor going bad and causing this leak. Could be cracked though

Thank you. I tried to look some feedback here but didn't find the answer yet. That's exactly my first thought: o-ring or a crack underneath. It's leaking through the sensor, which is quite weird.

Will search again with a bit more time.

[E92William]

Originally Posted by ruimpinho

Thank you. I tried to look some feedback here but didn't find the answer yet. That's exactly my first thought: o-ring or a crack underneath. It's leaking through the sensor, which is quite weird.

Will search again with a bit more time.

I just did a bit of research and turns out that sensor does not have an o ring. It seems to work via maybe Hall effect or magnet and it reads according to what it senses from the float inside the tank moving up and down, interesting. I don't think it even contacts the coolant at all. However if it is leaking there like it's visible I think either the lower hose/elbow on the reservoir is cracked and leaking down over the sensor or the reservoir has an internal crack that's leaking into where the sensor without any seal is. You should pull it out and have a look