Diagnostic Help? (coolant issue)

Hey Guys,

I just drove my new to me 2004 325Ci for about 500 miles and am having my first real mechanical issue (besides an SES light).

Quick scenario and question: I drove my car about 40 miles around town today with multiple stops... I got home parked in the garage and went out about an hour later. When I started my car the yellow coolant level light came on and I shut it down immediately. I looked under my car and there was a puddle of coolant towards the drivers side front... probably 2-4 cups worth of coolant. I am hoping someone has had this issue before or could suggest the first places to look for a leak or what could possibly be going wrong. I know that the entire cooling system is probably a good idea to replace (92,000 miles) but would like to find the main issue so that I could at least get the car drivable while I get the parts to do the whole system. Thanks again for anyone's input!

Could be expansion tank crack or the hose that connects to it is ruptures. Get under there with a flashlight and look around.

maybe cracked expansion tank. check if your tank is leaking.

Sorry for the dumb question... (haven't even gotten any manuals on the car yet) Could you please tell me the whereabouts of the expansion tank... I'm hoping its on the drivers side....

If you are standing at the front of the car it is on your right side. It is where you fill the coolant. Check closely, sometimes you can't even tell they are busted.
At 92k I would replace everything except the radiator.
Upper and lower coolant hose
water pump
thermostat
expansion tank (obviously)
Coolant temp. sensor
and there are two hoses from the expansion tank to the motor. One of them is very easy but I'm not sure about the other.

Welcome to the club!

Thanks for the reply.. I kept looking for another "tank" but I figured it out from the RealOEM diagrams of the system. Replacing the cooling system components is on my "to do" especially the water pump. I ordered that specialty tool for the water pump fan tonight! Can anyone think of what component would cause the coolant to leak only after the engine has been on and warmed up... I can't find any active leaks when the engine is running but after its shut down is when it appears to leak a few cups of coolant out. I am going to try tomorrow in the daylight to pinpoint where this is coming from.

expansion tank

Maybe the way the pressure builds up has something to do with it? Feel free to message me when you change stuff if you run into any problems. When you replace the t-stat and water pump, make sure you clean the engine block really well otherwise you'll get small leaks. Ask me how I know...

The reason to do the entire system at once is b/c you are dissassembling most of the system to remove the expansion tank (which is probably the culprit). Thus, you could just replace the tank, but you will have to remove a bunch of the same stuff if you decide to later to the other parts.

Just an update for anyone else facing this problem. The issue did turn out to be the radiator expansion tank. I used the DIY's on this site and some others to replace it this afternoon and the problem is solved. Thanks again to everyone who posted suggestions.