[BluesDriver]

This is on a 2011 328i.

In the past 5000 miles my coolant level has gone down about 8 ounces and there have been a couple of times where I thought I smelled coolant through the vents. About a year ago I brought it into the service department for this possible issue and after leak testing it overnight, they said there were no leaks.

Although I do not think a car should loose any coolant, is this considered normal and does any one else have the same issue?

[fun2drive]

8oz is NOT normal something is up. I have had issues with a similar issue and you cannot find the source while warm or hot but shows a few drops cold. Did they pressure test the system cold?
I am guessing you have a crack in one of the components causing a leak that might not be detected until cold. Lets hope it isn't a cylinder head issue too which can do the same things...

[BluesDriver]

I don't know how hot the engine was when they first tested it but they tested it during the day and did not find any leaks. They then kept it pressure tested overnight and still showed no leaks.

[mike3000fl]

I kept losing coolant too. Half the time when I would overheat I cant tell if it's because the car lost coolant and then overheated, or the waterpump took a temporary shit. In the end I replaced the expansion tank cap. I figure maybe the spring in it is weak and it is venting coolant on hot days.

[BluesDriver]

Bump!

[drunkenup]

Coolant goes somewhere.. if its not the system, it might be going through the engine like fun2drive said. My mom's Audi Q5 had a bad head gasket that slowly burnt coolant and got worse gradually until you could smell and see coolant through the exhaust. Ironically, my e92's coolant expansion tank is leaking at the edge near the top and spews coolant around that area...

My only suggestion is to document how full it is now (when cold) and keep checking on it over the next couple of weeks. If coolant continues to disappear you should go back to the dealer. It is either going through your engine or is leaking somewhere, which could lead to a catastrophic failure later. Good luck!

[Efthreeoh]

Try a new coolant reservoir cap first, they are about $11. The cap is designed to vent the system when there is an over pressure situation. If the coolant pump goes the system can over-pressure quite quickly and the cap can be degraded where it will let a normally operating system vent coolant as vapor. A new cap will solve that problem.

There is no mystery to a cooling system, it either has a physical leak you can see, it looses coolant internally through engine problems via a bad head gasket (or in the case of a N52/54 a bad oil filter housing gasket), or a bad reservoir cap.

[gds52]

Make sure it doent leak. If it leaks it would be around passenger door and passenger side fender. Its 2011 car, there shouldnt be any leakage, but make sure it doesnt leak.

[BluesDriver]

I will definitely keep my eye on this and check for any leaks from the heater core. In any case the dealer will be seeing me again.

One thing I didn't mention is that I first started noticing this after the first "free" oil change. When I started smelling coolant I checked the reservoir and it was overfilled. Maybe it got over pressurized and either caused some seal to fail or as Efthreeoh said it ruined the cap.

[chronos6]

Originally Posted by Efthreeoh

Try a new coolant reservoir cap first, they are about $11. The cap is designed to vent the system when there is an over pressure situation. If the coolant pump goes the system can over-pressure quite quickly and the cap can be degraded where it will let a normally operating system vent coolant as vapor. A new cap will solve that problem.

There is no mystery to a cooling system, it either has a physical leak you can see, it looses coolant internally through engine problems via a bad head gasket (or in the case of a N52/54 a bad oil filter housing gasket), or a bad reservoir cap.

The cap must be my problem why I see vapor exiting from my passenger kidney grill as if the car was smoking (light smoke/vapor). But that may mean my coolant pump is taking a shit and will crap out sooner or later.