Hey so weird stuff started on my e39 its a 525d

Was going back home when my car suddenly stopped heating had this happen before 2 or 3 times but i would just add coolant because level dropped and be on with it

last time same happened but when i opened expansion tank(hope spelled the right part) to top it off i had a weird bubly foam like in it. Still had few kms to drive back so i added few bits of coolant and left car to sit when i came back. At first peeps said oil might be mixing with coolant and making it foamy so we drained all coolant replaced it with water ran it till car warmed up and there was no oil nothing in it so we drained it out filled it with coolant and just rode around like that while checking it from time to time everything was ok until one check the coolant tank was dry empty. Car was warmed up and not overheating. Stopped turned ignition off opened the coolant tank went to grab some coolant and when i got back some antifreeze was pouring back in. So topped it back up went back home and left car to sit till i sort out what problem might be but the more forums i read the more different solutions there might be for it makes me feel like i should just change the whole cooling system. P.S. as far as i understand the head is not blown since the oil is dark as is. when i checked the dipstick no milky stuff or anything weird in oil. No white smoke when running the car.


the car:e39 525d 2002 auto

oil is not milky

No white smoke from exaust

no puddles under the car

dont see oil in coolant

engine not overheating

car is not chipped. full stock


Hope someone would be able to pinpoint me to a useful direction i should start since i might not need to swap the whole cooling system. Would feel dumb either if after replacing problem would still be there. Will be grateful for any help.

P.S. might have made some grammar mistakes. Hope its understamdable enough.