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Hey I need some help . I have a 2011 BMW 328xi 58k miles. So about a week ago I got a low coolant warning . No signs of leak anywhere. I filled up and noticed I started leaking a bit not much . Recently it has not lost any coolant that is in there but something sure Is leaking. I'm not sure if it's the radiator or a hose ? I have not got any warnings now but of course I want to fix before it gets worse. Is there a common leak with e90s ? Radiator? Hose? I also want to purchase a coder to diagnose any future faults or problems with my car what would be the best coder to use for my n52 ? TIA

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...2011 BMW 328xi...a week ago I got a low coolant warning . No signs of leak anywhere. I filled up and noticed I started leaking a bit not much . Recently it has not lost any coolant that is in there but something sure Is leaking...I have not got any warnings now... Is there a common leak with e90s ?

I also want to purchase a coder to diagnose any future faults or problems with my car what would be the best coder to use for my n52 ?
Welcome to the Forum! Working backwards, are you SURE you have an N52 (since you are in San Diego) as I thought most 328i/xi in CA were N51 (SULEV). It DOES make a difference as far as warranty (100,000 mi. warranty on certain SULEV components). If you look at the labels on the front of your engine compartment you should see identification as either SULEV or ULEV.

Scan Tool to Read/Clear Codes:
Have you ever used a scan tool, and do you have a Windows 10 OS Laptop? If you are new to using a Scan Tool that connects to the OBD II socket of your vehicle to read codes, and you just want to do basic OBD II engine code reading (best way to get started) AND particularly if you ALSO have a NON-BMW that you want to be able to read/clear codes on, I would recommend starting with a basic P-code Reader that can handle most Engine Control Module codes (most anything that sets the SES light). While this CANNOT read Fault Codes in other modules of the vehicle, it is MUCH quicker & easier to master (several hours of reading manual and testing its use on your vehicle). You can get a "standalone" unit that does NOT require any other hardware such as a laptop, tablet or smartphone, or any other cable connector than the one that is attached to the unit. Cost for good unit of that type ~ $35, such as this one:
https://www.amazon.com/Autel-AutoLi...545195749&sr=8-3&keywords=autel+319+scan+tool

Here's the Manual if you want to understand what it can do & how to use it:
https://images-na.ssl-images-amazon.com/images/I/91nwJvgr44L.pdf

If you have a laptop, I would suggest this one ($30; I have used BOTH of these linked units):
https://www.amazon.com/ScanTool-OBD...ie=UTF8&qid=1545196108&sr=8-3&keywords=obdwiz

If you want to be a diagnostics pro, have a Windows 10 Laptop, and don't mind spending hours to learn how to use what dealer techs use, get a K+DCAN cable for $15 to $45 and free download of INPA or ISTA software (post back for details).

Of course DTCs (Diagnostic Fault Codes) are of NO use in locating a coolant leak. :tsk:

Low Coolant Warning/Coolant Leak?:

I understand that you had a Low Coolant Level warning light, topped up the Coolant Reservoir and the light went out?

I do NOT understand the rest of your description. I assume you are aware that you have a splash shield under the engine which can hold coolant or any other liquid that has gotten on top of the shield, and leak it at a later time depending on how the vehicle is parked, etc.

The best simple way I know to identify the source of a leak is to remove the undershields. There is one under engine, one in front of that under radiator, and there is a third one behind engine under transmission which you do NOT need to remove for this purpose. Run engine until it reaches normal operating temp and then shutdown so that coolant vapor pressure "pressurizes" the cooling system. Then immediately put cardboard beneath radiator and engine, and see if any coolant/liquid falls on cardboard. If any drips, note what is immediately ABOVE that drip spot and try to follow/ trace upwards to leak source.

A more technically-elegant method is to put UV dye in the cooling system & use UV light & glasses to trace leak path.

Many of the BMW Cooling System hoses have O-ring seals and plastic fittings. The o-rings can leak, the plastic fittings can get brittle & crack, or of course a hose or even the radiator may develop a pin-hole leak. There is a gasket at the Oil Filter Housing (OFH) where coolant is in one passage and oil in another, and if that gasket fails in a certain way, you can get an internal leak of coolant into the oil (NOT good), but that is NOT your situation if you see an external leak or drip. Perhaps the most frequently-encountered leak is at the small "Bypass Hose" that runs from just below the OFH on the front of the engine, downward and to the passenger side where the Thermostat is located. That hose, just below the OFH, has both an o-ring, AND a plastic fitting, either of which may fail. The sealing ring on the Coolant Reservoir cap can also leak, or even the reservoir itself, so there is NO single likely culprit, you just need to work upward from a drip after hot shutdown as described above.

Please let us know what you find,
George
 
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